From: Paul Durrant <[email protected]>
This series has some small fixes from what was in version 10 [1]:
* KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA
This required a small fix to kvm_gpc_check() for an error that was
introduced in version 8.
* KVM: xen: separate initialization of shared_info cache and content
This accidentally regressed a fix in commit 5d6d6a7d7e66a ("KVM: x86:
Refine calculation of guest wall clock to use a single TSC read").
* KVM: xen: re-initialize shared_info if guest (32/64-bit) mode is set
This mistakenly removed the initialization of shared_info from the code
setting the KVM_XEN_ATTR_TYPE_SHARED_INFO attribute, which broke the self-
tests.
* KVM: xen: split up kvm_xen_set_evtchn_fast()
This had a /32 and a /64 swapped in set_vcpu_info_evtchn_pending().
[1] https://lore.kernel.org/kvm/[email protected]/
Paul Durrant (19):
KVM: pfncache: Add a map helper function
KVM: pfncache: remove unnecessary exports
KVM: xen: mark guest pages dirty with the pfncache lock held
KVM: pfncache: add a mark-dirty helper
KVM: pfncache: remove KVM_GUEST_USES_PFN usage
KVM: pfncache: stop open-coding offset_in_page()
KVM: pfncache: include page offset in uhva and use it consistently
KVM: pfncache: allow a cache to be activated with a fixed (userspace)
HVA
KVM: xen: separate initialization of shared_info cache and content
KVM: xen: re-initialize shared_info if guest (32/64-bit) mode is set
KVM: xen: allow shared_info to be mapped by fixed HVA
KVM: xen: allow vcpu_info to be mapped by fixed HVA
KVM: selftests / xen: map shared_info using HVA rather than GFN
KVM: selftests / xen: re-map vcpu_info using HVA rather than GPA
KVM: xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability
KVM: xen: split up kvm_xen_set_evtchn_fast()
KVM: xen: don't block on pfncache locks in kvm_xen_set_evtchn_fast()
KVM: pfncache: check the need for invalidation under read lock first
KVM: xen: allow vcpu_info content to be 'safely' copied
Documentation/virt/kvm/api.rst | 53 ++-
arch/x86/kvm/x86.c | 7 +-
arch/x86/kvm/xen.c | 360 +++++++++++-------
include/linux/kvm_host.h | 40 +-
include/linux/kvm_types.h | 8 -
include/uapi/linux/kvm.h | 9 +-
.../selftests/kvm/x86_64/xen_shinfo_test.c | 59 ++-
virt/kvm/pfncache.c | 188 ++++-----
8 files changed, 466 insertions(+), 258 deletions(-)
base-commit: f2a3fb7234e52f72ff4a38364dbf639cf4c7d6c6
--
2.39.2
From: Paul Durrant <[email protected]>
Taking a write lock on a pfncache will be disruptive if the cache is
heavily used (which only requires a read lock). Hence, in the MMU notifier
callback, take read locks on caches to check for a match; only taking a
write lock to actually perform an invalidation (after a another check).
Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
---
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: David Woodhouse <[email protected]>
v10:
- New in this version.
---
virt/kvm/pfncache.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index ae822bff812f..70394d7c9a38 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -29,14 +29,30 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start,
spin_lock(&kvm->gpc_lock);
list_for_each_entry(gpc, &kvm->gpc_list, list) {
- write_lock_irq(&gpc->lock);
+ read_lock_irq(&gpc->lock);
/* Only a single page so no need to care about length */
if (gpc->valid && !is_error_noslot_pfn(gpc->pfn) &&
gpc->uhva >= start && gpc->uhva < end) {
- gpc->valid = false;
+ read_unlock_irq(&gpc->lock);
+
+ /*
+ * There is a small window here where the cache could
+ * be modified, and invalidation would no longer be
+ * necessary. Hence check again whether invalidation
+ * is still necessary once the write lock has been
+ * acquired.
+ */
+
+ write_lock_irq(&gpc->lock);
+ if (gpc->valid && !is_error_noslot_pfn(gpc->pfn) &&
+ gpc->uhva >= start && gpc->uhva < end)
+ gpc->valid = false;
+ write_unlock_irq(&gpc->lock);
+ continue;
}
- write_unlock_irq(&gpc->lock);
+
+ read_unlock_irq(&gpc->lock);
}
spin_unlock(&kvm->gpc_lock);
}
--
2.39.2
From: Paul Durrant <[email protected]>
Using the HVA of the shared_info page is more efficient, so if the
capability (KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA) is present use that method
to do the mapping.
NOTE: Have the juggle_shinfo_state() thread map and unmap using both
GFN and HVA, to make sure the older mechanism is not broken.
Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
---
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: David Woodhouse <[email protected]>
v3:
- Re-work the juggle_shinfo_state() thread.
v2:
- New in this version.
---
.../selftests/kvm/x86_64/xen_shinfo_test.c | 44 +++++++++++++++----
1 file changed, 35 insertions(+), 9 deletions(-)
diff --git a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
index 9ec9ab60b63e..a61500ff0822 100644
--- a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
@@ -389,6 +389,7 @@ static int cmp_timespec(struct timespec *a, struct timespec *b)
return 0;
}
+static struct shared_info *shinfo;
static struct vcpu_info *vinfo;
static struct kvm_vcpu *vcpu;
@@ -404,20 +405,38 @@ static void *juggle_shinfo_state(void *arg)
{
struct kvm_vm *vm = (struct kvm_vm *)arg;
- struct kvm_xen_hvm_attr cache_activate = {
+ struct kvm_xen_hvm_attr cache_activate_gfn = {
.type = KVM_XEN_ATTR_TYPE_SHARED_INFO,
.u.shared_info.gfn = SHINFO_REGION_GPA / PAGE_SIZE
};
- struct kvm_xen_hvm_attr cache_deactivate = {
+ struct kvm_xen_hvm_attr cache_deactivate_gfn = {
.type = KVM_XEN_ATTR_TYPE_SHARED_INFO,
.u.shared_info.gfn = KVM_XEN_INVALID_GFN
};
+ struct kvm_xen_hvm_attr cache_activate_hva = {
+ .type = KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA,
+ .u.shared_info.hva = (unsigned long)shinfo
+ };
+
+ struct kvm_xen_hvm_attr cache_deactivate_hva = {
+ .type = KVM_XEN_ATTR_TYPE_SHARED_INFO,
+ .u.shared_info.hva = 0
+ };
+
+ int xen_caps = kvm_check_cap(KVM_CAP_XEN_HVM);
+
for (;;) {
- __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_activate);
- __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_deactivate);
+ __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_activate_gfn);
pthread_testcancel();
+ __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_deactivate_gfn);
+
+ if (xen_caps & KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA) {
+ __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_activate_hva);
+ pthread_testcancel();
+ __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_deactivate_hva);
+ }
}
return NULL;
@@ -442,6 +461,7 @@ int main(int argc, char *argv[])
bool do_runstate_flag = !!(xen_caps & KVM_XEN_HVM_CONFIG_RUNSTATE_UPDATE_FLAG);
bool do_eventfd_tests = !!(xen_caps & KVM_XEN_HVM_CONFIG_EVTCHN_2LEVEL);
bool do_evtchn_tests = do_eventfd_tests && !!(xen_caps & KVM_XEN_HVM_CONFIG_EVTCHN_SEND);
+ bool has_shinfo_hva = !!(xen_caps & KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA);
clock_gettime(CLOCK_REALTIME, &min_ts);
@@ -452,7 +472,7 @@ int main(int argc, char *argv[])
SHINFO_REGION_GPA, SHINFO_REGION_SLOT, 3, 0);
virt_map(vm, SHINFO_REGION_GVA, SHINFO_REGION_GPA, 3);
- struct shared_info *shinfo = addr_gpa2hva(vm, SHINFO_VADDR);
+ shinfo = addr_gpa2hva(vm, SHINFO_VADDR);
int zero_fd = open("/dev/zero", O_RDONLY);
TEST_ASSERT(zero_fd != -1, "Failed to open /dev/zero");
@@ -488,10 +508,16 @@ int main(int argc, char *argv[])
"Failed to read back RUNSTATE_UPDATE_FLAG attr");
}
- struct kvm_xen_hvm_attr ha = {
- .type = KVM_XEN_ATTR_TYPE_SHARED_INFO,
- .u.shared_info.gfn = SHINFO_REGION_GPA / PAGE_SIZE,
- };
+ struct kvm_xen_hvm_attr ha = {};
+
+ if (has_shinfo_hva) {
+ ha.type = KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA;
+ ha.u.shared_info.hva = (unsigned long)shinfo;
+ } else {
+ ha.type = KVM_XEN_ATTR_TYPE_SHARED_INFO;
+ ha.u.shared_info.gfn = SHINFO_ADDR / PAGE_SIZE;
+ }
+
vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &ha);
/*
--
2.39.2
From: Paul Durrant <[email protected]>
If the relevant capability (KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA) is present
then re-map vcpu_info using the HVA part way through the tests to make sure
then there is no functional change.
Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
---
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: David Woodhouse <[email protected]>
v5:
- New in this version.
---
.../selftests/kvm/x86_64/xen_shinfo_test.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
index a61500ff0822..d2ea0435f4f7 100644
--- a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
@@ -62,6 +62,7 @@ enum {
TEST_POLL_TIMEOUT,
TEST_POLL_MASKED,
TEST_POLL_WAKE,
+ SET_VCPU_INFO,
TEST_TIMER_PAST,
TEST_LOCKING_SEND_RACE,
TEST_LOCKING_POLL_RACE,
@@ -321,6 +322,10 @@ static void guest_code(void)
GUEST_SYNC(TEST_POLL_WAKE);
+ /* Set the vcpu_info to point at exactly the place it already is to
+ * make sure the attribute is functional. */
+ GUEST_SYNC(SET_VCPU_INFO);
+
/* A timer wake an *unmasked* port which should wake us with an
* actual interrupt, while we're polling on a different port. */
ports[0]++;
@@ -888,6 +893,16 @@ int main(int argc, char *argv[])
alarm(1);
break;
+ case SET_VCPU_INFO:
+ if (has_shinfo_hva) {
+ struct kvm_xen_vcpu_attr vih = {
+ .type = KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA,
+ .u.hva = (unsigned long)vinfo
+ };
+ vcpu_ioctl(vcpu, KVM_XEN_VCPU_SET_ATTR, &vih);
+ }
+ break;
+
case TEST_TIMER_PAST:
TEST_ASSERT(!evtchn_irq_expected,
"Expected event channel IRQ but it didn't happen");
--
2.39.2
From: Paul Durrant <[email protected]>
If the shared_info PFN cache has already been initialized then the content
of the shared_info page needs to be re-initialized whenever the guest
mode is (re)set.
Setting the guest mode is either done explicitly by the VMM via the
KVM_XEN_ATTR_TYPE_LONG_MODE attribute, or implicitly when the guest writes
the MSR to set up the hypercall page.
Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
---
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: [email protected]
v11:
- Drop the hunk removing the call to kvm_xen_shared_info_init() when
KVM_XEN_ATTR_TYPE_SHARED_INFO is set; it was a mistake and causes self-
test failures.
v10:
- New in this version.
---
arch/x86/kvm/xen.c | 33 +++++++++++++++++++++++++++++----
1 file changed, 29 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index df53fea73747..27d0e89fc4ab 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -623,10 +623,20 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
if (!IS_ENABLED(CONFIG_64BIT) && data->u.long_mode) {
r = -EINVAL;
} else {
+ bool lm = !!data->u.long_mode;
+
mutex_lock(&kvm->arch.xen.xen_lock);
- kvm->arch.xen.long_mode = !!data->u.long_mode;
+ if (kvm->arch.xen.long_mode != lm) {
+ kvm->arch.xen.long_mode = lm;
+
+ /*
+ * Re-initialize shared_info to put the wallclock in the
+ * correct place.
+ */
+ r = kvm->arch.xen.shinfo_cache.active ?
+ kvm_xen_shared_info_init(kvm) : 0;
+ }
mutex_unlock(&kvm->arch.xen.xen_lock);
- r = 0;
}
break;
@@ -1101,9 +1111,24 @@ int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data)
u32 page_num = data & ~PAGE_MASK;
u64 page_addr = data & PAGE_MASK;
bool lm = is_long_mode(vcpu);
+ int r = 0;
+
+ mutex_lock(&kvm->arch.xen.xen_lock);
+ if (kvm->arch.xen.long_mode != lm) {
+ kvm->arch.xen.long_mode = lm;
+
+ /*
+ * Re-initialize shared_info to put the wallclock in the
+ * correct place.
+ */
+ if (kvm->arch.xen.shinfo_cache.active &&
+ kvm_xen_shared_info_init(kvm))
+ r = 1;
+ }
+ mutex_unlock(&kvm->arch.xen.xen_lock);
- /* Latch long_mode for shared_info pages etc. */
- vcpu->kvm->arch.xen.long_mode = lm;
+ if (r)
+ return r;
/*
* If Xen hypercall intercept is enabled, fill the hypercall
--
2.39.2
From: Paul Durrant <[email protected]>
Now that all relevant kernel changes and selftests are in place, enable the
new capability.
Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
---
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: [email protected]
v2:
- New in this version.
---
arch/x86/kvm/x86.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 19e6cc1dadfe..4864251dca41 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4678,7 +4678,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
KVM_XEN_HVM_CONFIG_SHARED_INFO |
KVM_XEN_HVM_CONFIG_EVTCHN_2LEVEL |
KVM_XEN_HVM_CONFIG_EVTCHN_SEND |
- KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE;
+ KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE |
+ KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA;
if (sched_info_on())
r |= KVM_XEN_HVM_CONFIG_RUNSTATE |
KVM_XEN_HVM_CONFIG_RUNSTATE_UPDATE_FLAG;
--
2.39.2
From: Paul Durrant <[email protected]>
The implementation of kvm_xen_set_evtchn_fast() is a rather lengthy piece
of code that performs two operations: updating of the shared_info
evtchn_pending mask, and updating of the vcpu_info evtchn_pending_sel
mask. Introduce a separate function to perform each of those operations and
re-work kvm_xen_set_evtchn_fast() to use them.
No functional change intended.
Signed-off-by: Paul Durrant <[email protected]>
---
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: [email protected]
v11:
- Fixed /64 vs /32 switcheroo and changed type of port_word_bit back to
int.
v10:
- Updated in this version. Dropped David'd R-b since the updates are
non-trivial.
v8:
- New in this version.
---
arch/x86/kvm/xen.c | 175 ++++++++++++++++++++++++++-------------------
1 file changed, 100 insertions(+), 75 deletions(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 9b8f9f8e2da2..4ebd24c3ae70 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1667,6 +1667,101 @@ static void kvm_xen_check_poller(struct kvm_vcpu *vcpu, int port)
}
}
+static int set_shinfo_evtchn_pending(struct kvm_vcpu *vcpu, u32 port)
+{
+ struct kvm *kvm = vcpu->kvm;
+ struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache;
+ unsigned long *pending_bits, *mask_bits;
+ unsigned long flags;
+ int rc = -EWOULDBLOCK;
+
+ read_lock_irqsave(&gpc->lock, flags);
+ if (!kvm_gpc_check(gpc, PAGE_SIZE))
+ goto out;
+
+ if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
+ struct shared_info *shinfo = gpc->khva;
+
+ pending_bits = (unsigned long *)&shinfo->evtchn_pending;
+ mask_bits = (unsigned long *)&shinfo->evtchn_mask;
+ } else {
+ struct compat_shared_info *shinfo = gpc->khva;
+
+ pending_bits = (unsigned long *)&shinfo->evtchn_pending;
+ mask_bits = (unsigned long *)&shinfo->evtchn_mask;
+ }
+
+ if (test_and_set_bit(port, pending_bits)) {
+ rc = 0; /* It was already raised */
+ } else if (test_bit(port, mask_bits)) {
+ rc = -ENOTCONN; /* It is masked */
+ kvm_xen_check_poller(vcpu, port);
+ } else {
+ rc = 1; /* It is newly raised */
+ }
+
+ out:
+ read_unlock_irqrestore(&gpc->lock, flags);
+ return rc;
+}
+
+static bool set_vcpu_info_evtchn_pending(struct kvm_vcpu *vcpu, u32 port)
+{
+ struct kvm *kvm = vcpu->kvm;
+ struct gfn_to_pfn_cache *gpc = &vcpu->arch.xen.vcpu_info_cache;
+ unsigned long flags;
+ bool kick_vcpu = false;
+
+ read_lock_irqsave(&gpc->lock, flags);
+
+ /*
+ * Try to deliver the event directly to the vcpu_info. If successful and
+ * the guest is using upcall_vector delivery, send the MSI.
+ * If the pfncache is invalid, set the shadow. In this case, or if the
+ * guest is using another form of event delivery, the vCPU must be
+ * kicked to complete the delivery.
+ */
+ if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
+ struct vcpu_info *vcpu_info = gpc->khva;
+ int port_word_bit = port / 64;
+
+ if (!kvm_gpc_check(gpc, sizeof(*vcpu_info))) {
+ if (!test_and_set_bit(port_word_bit, &vcpu->arch.xen.evtchn_pending_sel))
+ kick_vcpu = true;
+ goto out;
+ }
+
+ if (!test_and_set_bit(port_word_bit, &vcpu_info->evtchn_pending_sel)) {
+ WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
+ kick_vcpu = true;
+ }
+ } else {
+ struct compat_vcpu_info *vcpu_info = gpc->khva;
+ int port_word_bit = port / 32;
+
+ if (!kvm_gpc_check(gpc, sizeof(*vcpu_info))) {
+ if (!test_and_set_bit(port_word_bit, &vcpu->arch.xen.evtchn_pending_sel))
+ kick_vcpu = true;
+ goto out;
+ }
+
+ if (!test_and_set_bit(port_word_bit,
+ (unsigned long *)&vcpu_info->evtchn_pending_sel)) {
+ WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
+ kick_vcpu = true;
+ }
+ }
+
+ if (kick_vcpu && vcpu->arch.xen.upcall_vector) {
+ kvm_xen_inject_vcpu_vector(vcpu);
+ kick_vcpu = false;
+ }
+
+ out:
+ read_unlock_irqrestore(&gpc->lock, flags);
+ return kick_vcpu;
+}
+
/*
* The return value from this function is propagated to kvm_set_irq() API,
* so it returns:
@@ -1675,15 +1770,12 @@ static void kvm_xen_check_poller(struct kvm_vcpu *vcpu, int port)
* > 0 Number of CPUs interrupt was delivered to
*
* It is also called directly from kvm_arch_set_irq_inatomic(), where the
- * only check on its return value is a comparison with -EWOULDBLOCK'.
+ * only check on its return value is a comparison with -EWOULDBLOCK
+ * (which may be returned by set_shinfo_evtchn_pending()).
*/
int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
{
- struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache;
struct kvm_vcpu *vcpu;
- unsigned long *pending_bits, *mask_bits;
- unsigned long flags;
- int port_word_bit;
bool kick_vcpu = false;
int vcpu_idx, idx, rc;
@@ -1703,79 +1795,12 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
if (xe->port >= max_evtchn_port(kvm))
return -EINVAL;
- rc = -EWOULDBLOCK;
-
idx = srcu_read_lock(&kvm->srcu);
- read_lock_irqsave(&gpc->lock, flags);
- if (!kvm_gpc_check(gpc, PAGE_SIZE))
- goto out_rcu;
-
- if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
- struct shared_info *shinfo = gpc->khva;
- pending_bits = (unsigned long *)&shinfo->evtchn_pending;
- mask_bits = (unsigned long *)&shinfo->evtchn_mask;
- port_word_bit = xe->port / 64;
- } else {
- struct compat_shared_info *shinfo = gpc->khva;
- pending_bits = (unsigned long *)&shinfo->evtchn_pending;
- mask_bits = (unsigned long *)&shinfo->evtchn_mask;
- port_word_bit = xe->port / 32;
- }
+ rc = set_shinfo_evtchn_pending(vcpu, xe->port);
+ if (rc == 1) /* Delivered to the bitmap in shared_info */
+ kick_vcpu = set_vcpu_info_evtchn_pending(vcpu, xe->port);
- /*
- * If this port wasn't already set, and if it isn't masked, then
- * we try to set the corresponding bit in the in-kernel shadow of
- * evtchn_pending_sel for the target vCPU. And if *that* wasn't
- * already set, then we kick the vCPU in question to write to the
- * *real* evtchn_pending_sel in its own guest vcpu_info struct.
- */
- if (test_and_set_bit(xe->port, pending_bits)) {
- rc = 0; /* It was already raised */
- } else if (test_bit(xe->port, mask_bits)) {
- rc = -ENOTCONN; /* Masked */
- kvm_xen_check_poller(vcpu, xe->port);
- } else {
- rc = 1; /* Delivered to the bitmap in shared_info. */
- /* Now switch to the vCPU's vcpu_info to set the index and pending_sel */
- read_unlock_irqrestore(&gpc->lock, flags);
- gpc = &vcpu->arch.xen.vcpu_info_cache;
-
- read_lock_irqsave(&gpc->lock, flags);
- if (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {
- /*
- * Could not access the vcpu_info. Set the bit in-kernel
- * and prod the vCPU to deliver it for itself.
- */
- if (!test_and_set_bit(port_word_bit, &vcpu->arch.xen.evtchn_pending_sel))
- kick_vcpu = true;
- goto out_rcu;
- }
-
- if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
- struct vcpu_info *vcpu_info = gpc->khva;
- if (!test_and_set_bit(port_word_bit, &vcpu_info->evtchn_pending_sel)) {
- WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
- kick_vcpu = true;
- }
- } else {
- struct compat_vcpu_info *vcpu_info = gpc->khva;
- if (!test_and_set_bit(port_word_bit,
- (unsigned long *)&vcpu_info->evtchn_pending_sel)) {
- WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
- kick_vcpu = true;
- }
- }
-
- /* For the per-vCPU lapic vector, deliver it as MSI. */
- if (kick_vcpu && vcpu->arch.xen.upcall_vector) {
- kvm_xen_inject_vcpu_vector(vcpu);
- kick_vcpu = false;
- }
- }
-
- out_rcu:
- read_unlock_irqrestore(&gpc->lock, flags);
srcu_read_unlock(&kvm->srcu, idx);
if (kick_vcpu) {
--
2.39.2
From: Paul Durrant <[email protected]>
As described in [1] compiling with CONFIG_PROVE_RAW_LOCK_NESTING shows that
kvm_xen_set_evtchn_fast() is blocking on pfncache locks in IRQ context.
There is only actually blocking with PREEMPT_RT because the locks will
turned into mutexes. There is no 'raw' version of rwlock_t that can be used
to avoid that, so use read_trylock() and treat failure to lock the same as
an invalid cache.
[1] https://lore.kernel.org/lkml/[email protected]/T/#mbd06e5a04534ce9c0ee94bd8f1e8d942b2d45bd6
Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
---
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: [email protected]
v11:
- Amended the commit comment.
v10:
- New in this version.
---
arch/x86/kvm/xen.c | 30 ++++++++++++++++++++----------
1 file changed, 20 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 4ebd24c3ae70..845ff23c8399 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1675,10 +1675,13 @@ static int set_shinfo_evtchn_pending(struct kvm_vcpu *vcpu, u32 port)
unsigned long flags;
int rc = -EWOULDBLOCK;
- read_lock_irqsave(&gpc->lock, flags);
- if (!kvm_gpc_check(gpc, PAGE_SIZE))
+ local_irq_save(flags);
+ if (!read_trylock(&gpc->lock))
goto out;
+ if (!kvm_gpc_check(gpc, PAGE_SIZE))
+ goto out_unlock;
+
if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
struct shared_info *shinfo = gpc->khva;
@@ -1700,8 +1703,10 @@ static int set_shinfo_evtchn_pending(struct kvm_vcpu *vcpu, u32 port)
rc = 1; /* It is newly raised */
}
+ out_unlock:
+ read_unlock(&gpc->lock);
out:
- read_unlock_irqrestore(&gpc->lock, flags);
+ local_irq_restore(flags);
return rc;
}
@@ -1711,21 +1716,23 @@ static bool set_vcpu_info_evtchn_pending(struct kvm_vcpu *vcpu, u32 port)
struct gfn_to_pfn_cache *gpc = &vcpu->arch.xen.vcpu_info_cache;
unsigned long flags;
bool kick_vcpu = false;
+ bool locked;
- read_lock_irqsave(&gpc->lock, flags);
+ local_irq_save(flags);
+ locked = read_trylock(&gpc->lock);
/*
* Try to deliver the event directly to the vcpu_info. If successful and
* the guest is using upcall_vector delivery, send the MSI.
- * If the pfncache is invalid, set the shadow. In this case, or if the
- * guest is using another form of event delivery, the vCPU must be
- * kicked to complete the delivery.
+ * If the pfncache lock is contended or the cache is invalid, set the
+ * shadow. In this case, or if the guest is using another form of event
+ * delivery, the vCPU must be kicked to complete the delivery.
*/
if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
struct vcpu_info *vcpu_info = gpc->khva;
int port_word_bit = port / 64;
- if (!kvm_gpc_check(gpc, sizeof(*vcpu_info))) {
+ if ((!locked || !kvm_gpc_check(gpc, sizeof(*vcpu_info)))) {
if (!test_and_set_bit(port_word_bit, &vcpu->arch.xen.evtchn_pending_sel))
kick_vcpu = true;
goto out;
@@ -1739,7 +1746,7 @@ static bool set_vcpu_info_evtchn_pending(struct kvm_vcpu *vcpu, u32 port)
struct compat_vcpu_info *vcpu_info = gpc->khva;
int port_word_bit = port / 32;
- if (!kvm_gpc_check(gpc, sizeof(*vcpu_info))) {
+ if ((!locked || !kvm_gpc_check(gpc, sizeof(*vcpu_info)))) {
if (!test_and_set_bit(port_word_bit, &vcpu->arch.xen.evtchn_pending_sel))
kick_vcpu = true;
goto out;
@@ -1758,7 +1765,10 @@ static bool set_vcpu_info_evtchn_pending(struct kvm_vcpu *vcpu, u32 port)
}
out:
- read_unlock_irqrestore(&gpc->lock, flags);
+ if (locked)
+ read_unlock(&gpc->lock);
+
+ local_irq_restore(flags);
return kick_vcpu;
}
--
2.39.2
From: Paul Durrant <[email protected]>
The shared_info page is not guest memory as such. It is a dedicated page
allocated by the VMM and overlaid onto guest memory in a GFN chosen by the
guest and specified in the XENMEM_add_to_physmap hypercall. The guest may
even request that shared_info be moved from one GFN to another by
re-issuing that hypercall, but the HVA is never going to change.
Because the shared_info page is an overlay the memory slots need to be
updated in response to the hypercall. However, memory slot adjustment is
not atomic and, whilst all vCPUs are paused, there is still the possibility
that events may be delivered (which requires the shared_info page to be
updated) whilst the shared_info GPA is absent. The HVA is never absent
though, so it makes much more sense to use that as the basis for the
kernel's mapping.
Hence add a new KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA attribute type for this
purpose and a KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA flag to advertize its
availability. Don't actually advertize it yet though. That will be done in
a subsequent patch, which will also add tests for the new attribute type.
Also update the KVM API documentation with the new attribute and also fix
it up to consistently refer to 'shared_info' (with the underscore).
Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
---
Cc: David Woodhouse <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
v8:
- Re-base.
v2:
- Define the new attribute and capability but don't advertize the
capability yet.
- Add API documentation.
---
Documentation/virt/kvm/api.rst | 25 ++++++++++++++++------
arch/x86/kvm/xen.c | 39 ++++++++++++++++++++++++++--------
include/uapi/linux/kvm.h | 6 +++++-
3 files changed, 54 insertions(+), 16 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index dca83c65d97f..bb78371807f1 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -372,7 +372,7 @@ The bits in the dirty bitmap are cleared before the ioctl returns, unless
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is enabled. For more information,
see the description of the capability.
-Note that the Xen shared info page, if configured, shall always be assumed
+Note that the Xen shared_info page, if configured, shall always be assumed
to be dirty. KVM will not explicitly mark it such.
@@ -5499,8 +5499,9 @@ KVM_PV_ASYNC_CLEANUP_PERFORM
__u8 long_mode;
__u8 vector;
__u8 runstate_update_flag;
- struct {
+ union {
__u64 gfn;
+ __u64 hva;
} shared_info;
struct {
__u32 send_port;
@@ -5528,10 +5529,10 @@ type values:
KVM_XEN_ATTR_TYPE_LONG_MODE
Sets the ABI mode of the VM to 32-bit or 64-bit (long mode). This
- determines the layout of the shared info pages exposed to the VM.
+ determines the layout of the shared_info page exposed to the VM.
KVM_XEN_ATTR_TYPE_SHARED_INFO
- Sets the guest physical frame number at which the Xen "shared info"
+ Sets the guest physical frame number at which the Xen shared_info
page resides. Note that although Xen places vcpu_info for the first
32 vCPUs in the shared_info page, KVM does not automatically do so
and instead requires that KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO be used
@@ -5540,7 +5541,7 @@ KVM_XEN_ATTR_TYPE_SHARED_INFO
not be aware of the Xen CPU id which is used as the index into the
vcpu_info[] array, so may know the correct default location.
- Note that the shared info page may be constantly written to by KVM;
+ Note that the shared_info page may be constantly written to by KVM;
it contains the event channel bitmap used to deliver interrupts to
a Xen guest, amongst other things. It is exempt from dirty tracking
mechanisms — KVM will not explicitly mark the page as dirty each
@@ -5549,9 +5550,21 @@ KVM_XEN_ATTR_TYPE_SHARED_INFO
any vCPU has been running or any event channel interrupts can be
routed to the guest.
- Setting the gfn to KVM_XEN_INVALID_GFN will disable the shared info
+ Setting the gfn to KVM_XEN_INVALID_GFN will disable the shared_info
page.
+KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA
+ If the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA flag is also set in the
+ Xen capabilities, then this attribute may be used to set the
+ userspace address at which the shared_info page resides, which
+ will always be fixed in the VMM regardless of where it is mapped
+ in guest physical address space. This attribute should be used in
+ preference to KVM_XEN_ATTR_TYPE_SHARED_INFO as it avoids
+ unnecessary invalidation of an internal cache when the page is
+ re-mapped in guest physcial address space.
+
+ Setting the hva to zero will disable the shared_info page.
+
KVM_XEN_ATTR_TYPE_UPCALL_VECTOR
Sets the exception vector used to deliver Xen event channel upcalls.
This is the HVM-wide vector injected directly by the hypervisor
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 27d0e89fc4ab..8ea68c64a467 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -617,7 +617,6 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
{
int r = -ENOENT;
-
switch (data->type) {
case KVM_XEN_ATTR_TYPE_LONG_MODE:
if (!IS_ENABLED(CONFIG_64BIT) && data->u.long_mode) {
@@ -640,20 +639,32 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
}
break;
- case KVM_XEN_ATTR_TYPE_SHARED_INFO: {
+ case KVM_XEN_ATTR_TYPE_SHARED_INFO:
+ case KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA: {
int idx;
mutex_lock(&kvm->arch.xen.xen_lock);
idx = srcu_read_lock(&kvm->srcu);
- if (data->u.shared_info.gfn == KVM_XEN_INVALID_GFN) {
- kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache);
- r = 0;
+ if (data->type == KVM_XEN_ATTR_TYPE_SHARED_INFO) {
+ if (data->u.shared_info.gfn == KVM_XEN_INVALID_GFN) {
+ kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache);
+ r = 0;
+ } else {
+ r = kvm_gpc_activate(&kvm->arch.xen.shinfo_cache,
+ gfn_to_gpa(data->u.shared_info.gfn),
+ PAGE_SIZE);
+ }
} else {
- r = kvm_gpc_activate(&kvm->arch.xen.shinfo_cache,
- gfn_to_gpa(data->u.shared_info.gfn),
- PAGE_SIZE);
+ if (data->u.shared_info.hva == 0) {
+ kvm_gpc_deactivate(&kvm->arch.xen.shinfo_cache);
+ r = 0;
+ } else {
+ r = kvm_gpc_activate_hva(&kvm->arch.xen.shinfo_cache,
+ data->u.shared_info.hva,
+ PAGE_SIZE);
+ }
}
srcu_read_unlock(&kvm->srcu, idx);
@@ -717,13 +728,23 @@ int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
break;
case KVM_XEN_ATTR_TYPE_SHARED_INFO:
- if (kvm->arch.xen.shinfo_cache.active)
+ if (kvm->arch.xen.shinfo_cache.active &&
+ kvm->arch.xen.shinfo_cache.gpa != KVM_XEN_INVALID_GPA)
data->u.shared_info.gfn = gpa_to_gfn(kvm->arch.xen.shinfo_cache.gpa);
else
data->u.shared_info.gfn = KVM_XEN_INVALID_GFN;
r = 0;
break;
+ case KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA:
+ if (kvm->arch.xen.shinfo_cache.active &&
+ kvm->arch.xen.shinfo_cache.gpa == KVM_XEN_INVALID_GPA)
+ data->u.shared_info.hva = kvm->arch.xen.shinfo_cache.uhva;
+ else
+ data->u.shared_info.hva = 0;
+ r = 0;
+ break;
+
case KVM_XEN_ATTR_TYPE_UPCALL_VECTOR:
data->u.vector = kvm->arch.xen.upcall_vector;
r = 0;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 175420b26e36..1a878689a76e 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1319,6 +1319,7 @@ struct kvm_x86_mce {
#define KVM_XEN_HVM_CONFIG_EVTCHN_SEND (1 << 5)
#define KVM_XEN_HVM_CONFIG_RUNSTATE_UPDATE_FLAG (1 << 6)
#define KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE (1 << 7)
+#define KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA (1 << 8)
struct kvm_xen_hvm_config {
__u32 flags;
@@ -1834,9 +1835,10 @@ struct kvm_xen_hvm_attr {
__u8 long_mode;
__u8 vector;
__u8 runstate_update_flag;
- struct {
+ union {
__u64 gfn;
#define KVM_XEN_INVALID_GFN ((__u64)-1)
+ __u64 hva;
} shared_info;
struct {
__u32 send_port;
@@ -1878,6 +1880,8 @@ struct kvm_xen_hvm_attr {
#define KVM_XEN_ATTR_TYPE_XEN_VERSION 0x4
/* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_RUNSTATE_UPDATE_FLAG */
#define KVM_XEN_ATTR_TYPE_RUNSTATE_UPDATE_FLAG 0x5
+/* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA */
+#define KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA 0x6
/* Per-vCPU Xen attributes */
#define KVM_XEN_VCPU_GET_ATTR _IOWR(KVMIO, 0xca, struct kvm_xen_vcpu_attr)
--
2.39.2
On 19 December 2023 16:11:06 GMT, Paul Durrant <[email protected]> wrote:
>From: Paul Durrant <[email protected]>
>
>The implementation of kvm_xen_set_evtchn_fast() is a rather lengthy piece
>of code that performs two operations: updating of the shared_info
>evtchn_pending mask, and updating of the vcpu_info evtchn_pending_sel
>mask. Introduce a separate function to perform each of those operations and
>re-work kvm_xen_set_evtchn_fast() to use them.
>
>No functional change intended.
>
>Signed-off-by: Paul Durrant <[email protected]
Reviewed-by: <[email protected]>
Would still like to see the xen_shinfo_test use an evtchn port# which triggers the bug in the precious version.
From: Paul Durrant <[email protected]>
If the guest sets an explicit vcpu_info GPA then, for any of the first 32
vCPUs, the content of the default vcpu_info in the shared_info page must be
copied into the new location. Because this copy may race with event
delivery (which updates the 'evtchn_pending_sel' field in vcpu_info) there
needs to be a way to defer that until the copy is complete.
Happily there is already a shadow of 'evtchn_pending_sel' in kvm_vcpu_xen
that is used in atomic context if the vcpu_info PFN cache has been
invalidated so that the update of vcpu_info can be deferred until the
cache can be refreshed (on vCPU thread's the way back into guest context).
Also use this shadow if the vcpu_info cache has been *deactivated*, so that
the VMM can safely copy the vcpu_info content and then re-activate the
cache with the new GPA. To do this, stop considering an inactive vcpu_info
cache as a hard error in kvm_xen_set_evtchn_fast().
Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
---
Cc: David Woodhouse <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
v8:
- Update commit comment.
v6:
- New in this version.
---
arch/x86/kvm/xen.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 845ff23c8399..99eeb9b68a02 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1799,9 +1799,6 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
WRITE_ONCE(xe->vcpu_idx, vcpu->vcpu_idx);
}
- if (!vcpu->arch.xen.vcpu_info_cache.active)
- return -EINVAL;
-
if (xe->port >= max_evtchn_port(kvm))
return -EINVAL;
--
2.39.2
From: Paul Durrant <[email protected]>
If the guest does not explicitly set the GPA of vcpu_info structure in
memory then, for guests with 32 vCPUs or fewer, the vcpu_info embedded
in the shared_info page may be used. As described in a previous commit,
the shared_info page is an overlay at a fixed HVA within the VMM, so in
this case it also more optimal to activate the vcpu_info cache with a
fixed HVA to avoid unnecessary invalidation if the guest memory layout
is modified.
Signed-off-by: Paul Durrant <[email protected]>
Reviewed-by: David Woodhouse <[email protected]>
---
Cc: David Woodhouse <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
v8:
- Re-base.
v5:
- New in this version.
---
Documentation/virt/kvm/api.rst | 26 +++++++++++++++++++++-----
arch/x86/kvm/xen.c | 34 ++++++++++++++++++++++++++++------
include/uapi/linux/kvm.h | 3 +++
3 files changed, 52 insertions(+), 11 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index bb78371807f1..34c04e2c0e9b 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5535,11 +5535,12 @@ KVM_XEN_ATTR_TYPE_SHARED_INFO
Sets the guest physical frame number at which the Xen shared_info
page resides. Note that although Xen places vcpu_info for the first
32 vCPUs in the shared_info page, KVM does not automatically do so
- and instead requires that KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO be used
- explicitly even when the vcpu_info for a given vCPU resides at the
- "default" location in the shared_info page. This is because KVM may
- not be aware of the Xen CPU id which is used as the index into the
- vcpu_info[] array, so may know the correct default location.
+ and instead requires that KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO or
+ KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA be used explicitly even when
+ the vcpu_info for a given vCPU resides at the "default" location
+ in the shared_info page. This is because KVM may not be aware of
+ the Xen CPU id which is used as the index into the vcpu_info[]
+ array, so may know the correct default location.
Note that the shared_info page may be constantly written to by KVM;
it contains the event channel bitmap used to deliver interrupts to
@@ -5661,6 +5662,21 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO
on dirty logging. Setting the gpa to KVM_XEN_INVALID_GPA will disable
the vcpu_info.
+KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA
+ If the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA flag is also set in the
+ Xen capabilities, then this attribute may be used to set the
+ userspace address of the vcpu_info for a given vCPU. It should
+ only be used when the vcpu_info resides at the "default" location
+ in the shared_info page. In this case it is safe to assume the
+ userspace address will not change, because the shared_info page is
+ an overlay on guest memory and remains at a fixed host address
+ regardless of where it is mapped in guest physical address space
+ and hence unnecessary invalidation of an internal cache may be
+ avoided if the guest memory layout is modified.
+ If the vcpu_info does not reside at the "default" location then
+ it is not guaranteed to remain at the same host address and
+ hence the aforementioned cache invalidation is required.
+
KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
Sets the guest physical address of an additional pvclock structure
for a given vCPU. This is typically used for guest vsyscall support.
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 8ea68c64a467..9b8f9f8e2da2 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -781,20 +781,33 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
switch (data->type) {
case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO:
+ case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA:
/* No compat necessary here. */
BUILD_BUG_ON(sizeof(struct vcpu_info) !=
sizeof(struct compat_vcpu_info));
BUILD_BUG_ON(offsetof(struct vcpu_info, time) !=
offsetof(struct compat_vcpu_info, time));
- if (data->u.gpa == KVM_XEN_INVALID_GPA) {
- kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
- r = 0;
- break;
+ if (data->type == KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO) {
+ if (data->u.gpa == KVM_XEN_INVALID_GPA) {
+ kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
+ r = 0;
+ break;
+ }
+
+ r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache,
+ data->u.gpa, sizeof(struct vcpu_info));
+ } else {
+ if (data->u.hva == 0) {
+ kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
+ r = 0;
+ break;
+ }
+
+ r = kvm_gpc_activate_hva(&vcpu->arch.xen.vcpu_info_cache,
+ data->u.hva, sizeof(struct vcpu_info));
}
- r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache,
- data->u.gpa, sizeof(struct vcpu_info));
if (!r)
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
@@ -1023,6 +1036,15 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
r = 0;
break;
+ case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA:
+ if (vcpu->arch.xen.vcpu_info_cache.active &&
+ vcpu->arch.xen.vcpu_info_cache.gpa == KVM_XEN_INVALID_GPA)
+ data->u.hva = vcpu->arch.xen.vcpu_info_cache.uhva;
+ else
+ data->u.hva = 0;
+ r = 0;
+ break;
+
case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
if (vcpu->arch.xen.vcpu_time_info_cache.active)
data->u.gpa = vcpu->arch.xen.vcpu_time_info_cache.gpa;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 1a878689a76e..02da0cd4153d 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1899,6 +1899,7 @@ struct kvm_xen_vcpu_attr {
union {
__u64 gpa;
#define KVM_XEN_INVALID_GPA ((__u64)-1)
+ __u64 hva;
__u64 pad[8];
struct {
__u64 state;
@@ -1929,6 +1930,8 @@ struct kvm_xen_vcpu_attr {
#define KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID 0x6
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#define KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR 0x8
+/* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA */
+#define KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA 0x9
/* Secure Encrypted Virtualization command */
enum sev_cmd_id {
--
2.39.2