The arm64 kernel doesn't yet support the full generic entry
infrastructure. That being said, KVM/arm64 doesn't properly handle
TIF_NOTIFY_RESUME and could pick this up by switching to the generic
guest entry infrasturture.
Patch 1 adds a missing vCPU stat to ARM64 to record the number of signal
exits to userspace.
Patch 2 unhitches entry-kvm from entry-generic, as ARM64 doesn't
currently support the generic infrastructure.
Patch 3 replaces the open-coded entry handling with the generic xfer
function.
This series was tested on an Ampere Mt. Jade reference system. The
series cleanly applies to kvm/queue (note that this is deliberate as the
generic kvm stats patches have not yet propagated to kvm-arm/queue) at
the following commit:
8ad5e63649ff ("KVM: Don't take mmu_lock for range invalidation unless necessary")
Oliver Upton (3):
KVM: arm64: Record number of signal exits as a vCPU stat
entry: KVM: Allow use of generic KVM entry w/o full generic support
KVM: arm64: Use generic KVM xfer to guest work function
arch/arm64/include/asm/kvm_host.h | 1 +
arch/arm64/kvm/Kconfig | 1 +
arch/arm64/kvm/arm.c | 26 ++++++++++++++------------
arch/arm64/kvm/guest.c | 3 ++-
include/linux/entry-kvm.h | 6 +++++-
5 files changed, 23 insertions(+), 14 deletions(-)
--
2.32.0.554.ge1b32706d8-goog
Most other architectures that implement KVM record a statistic
indicating the number of times a vCPU has exited due to a pending
signal. Add support for that stat to arm64.
Cc: Jing Zhang <[email protected]>
Signed-off-by: Oliver Upton <[email protected]>
---
arch/arm64/include/asm/kvm_host.h | 1 +
arch/arm64/kvm/arm.c | 1 +
arch/arm64/kvm/guest.c | 3 ++-
3 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 41911585ae0c..70e129f2b574 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -576,6 +576,7 @@ struct kvm_vcpu_stat {
u64 wfi_exit_stat;
u64 mmio_exit_user;
u64 mmio_exit_kernel;
+ u64 signal_exits;
u64 exits;
};
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index e9a2b8f27792..60d0a546d7fd 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -783,6 +783,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
if (signal_pending(current)) {
ret = -EINTR;
run->exit_reason = KVM_EXIT_INTR;
+ ++vcpu->stat.signal_exits;
}
/*
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 1dfb83578277..50fc16ad872f 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -50,7 +50,8 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
STATS_DESC_COUNTER(VCPU, wfi_exit_stat),
STATS_DESC_COUNTER(VCPU, mmio_exit_user),
STATS_DESC_COUNTER(VCPU, mmio_exit_kernel),
- STATS_DESC_COUNTER(VCPU, exits)
+ STATS_DESC_COUNTER(VCPU, exits),
+ STATS_DESC_COUNTER(VCPU, signal_exits),
};
static_assert(ARRAY_SIZE(kvm_vcpu_stats_desc) ==
sizeof(struct kvm_vcpu_stat) / sizeof(u64));
--
2.32.0.554.ge1b32706d8-goog
Clean up handling of checks for pending work by switching to the generic
infrastructure to do so.
We pick up handling for TIF_NOTIFY_RESUME from this switch, meaning that
task work will be correctly handled.
Signed-off-by: Oliver Upton <[email protected]>
---
arch/arm64/kvm/Kconfig | 1 +
arch/arm64/kvm/arm.c | 27 ++++++++++++++-------------
2 files changed, 15 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index a4eba0908bfa..8bc1fac5fa26 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -26,6 +26,7 @@ menuconfig KVM
select HAVE_KVM_ARCH_TLB_FLUSH_ALL
select KVM_MMIO
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
+ select KVM_XFER_TO_GUEST_WORK
select SRCU
select KVM_VFIO
select HAVE_KVM_EVENTFD
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 60d0a546d7fd..9762e2129813 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -6,6 +6,7 @@
#include <linux/bug.h>
#include <linux/cpu_pm.h>
+#include <linux/entry-kvm.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/kvm_host.h>
@@ -714,6 +715,13 @@ static bool vcpu_mode_is_bad_32bit(struct kvm_vcpu *vcpu)
static_branch_unlikely(&arm64_mismatched_32bit_el0);
}
+static bool kvm_vcpu_exit_request(struct kvm_vcpu *vcpu)
+{
+ return kvm_request_pending(vcpu) ||
+ need_new_vmid_gen(&vcpu->arch.hw_mmu->vmid) ||
+ xfer_to_guest_mode_work_pending();
+}
+
/**
* kvm_arch_vcpu_ioctl_run - the main VCPU run function to execute guest code
* @vcpu: The VCPU pointer
@@ -757,7 +765,11 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
/*
* Check conditions before entering the guest
*/
- cond_resched();
+ if (__xfer_to_guest_mode_work_pending()) {
+ ret = xfer_to_guest_mode_handle_work(vcpu);
+ if (!ret)
+ ret = 1;
+ }
update_vmid(&vcpu->arch.hw_mmu->vmid);
@@ -776,16 +788,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
kvm_vgic_flush_hwstate(vcpu);
- /*
- * Exit if we have a signal pending so that we can deliver the
- * signal to user space.
- */
- if (signal_pending(current)) {
- ret = -EINTR;
- run->exit_reason = KVM_EXIT_INTR;
- ++vcpu->stat.signal_exits;
- }
-
/*
* If we're using a userspace irqchip, then check if we need
* to tell a userspace irqchip about timer or PMU level
@@ -809,8 +811,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
*/
smp_store_mb(vcpu->mode, IN_GUEST_MODE);
- if (ret <= 0 || need_new_vmid_gen(&vcpu->arch.hw_mmu->vmid) ||
- kvm_request_pending(vcpu)) {
+ if (ret <= 0 || kvm_vcpu_exit_request(vcpu)) {
vcpu->mode = OUTSIDE_GUEST_MODE;
isb(); /* Ensure work in x_flush_hwstate is committed */
kvm_pmu_sync_hwstate(vcpu);
--
2.32.0.554.ge1b32706d8-goog
Some architectures (e.g. arm64) have yet to adopt the generic entry
infrastructure. Despite that, it would be nice to use some common
plumbing for guest entry/exit handling. For example, KVM/arm64 currently
does not handle TIF_NOTIFY_PENDING correctly.
Allow use of only the generic KVM entry code by tightening up the
include list. No functional change intended.
Signed-off-by: Oliver Upton <[email protected]>
---
include/linux/entry-kvm.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
index 136b8d97d8c0..0d7865a0731c 100644
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -2,7 +2,11 @@
#ifndef __LINUX_ENTRYKVM_H
#define __LINUX_ENTRYKVM_H
-#include <linux/entry-common.h>
+#include <linux/static_call_types.h>
+#include <linux/tracehook.h>
+#include <linux/syscalls.h>
+#include <linux/seccomp.h>
+#include <linux/sched.h>
#include <linux/tick.h>
/* Transfer to guest mode work */
--
2.32.0.554.ge1b32706d8-goog
On Thu, Jul 29, 2021 at 12:56 PM Oliver Upton <[email protected]> wrote:
>
> Most other architectures that implement KVM record a statistic
> indicating the number of times a vCPU has exited due to a pending
> signal. Add support for that stat to arm64.
>
> Cc: Jing Zhang <[email protected]>
> Signed-off-by: Oliver Upton <[email protected]>
> ---
> arch/arm64/include/asm/kvm_host.h | 1 +
> arch/arm64/kvm/arm.c | 1 +
> arch/arm64/kvm/guest.c | 3 ++-
> 3 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 41911585ae0c..70e129f2b574 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -576,6 +576,7 @@ struct kvm_vcpu_stat {
> u64 wfi_exit_stat;
> u64 mmio_exit_user;
> u64 mmio_exit_kernel;
> + u64 signal_exits;
> u64 exits;
> };
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index e9a2b8f27792..60d0a546d7fd 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -783,6 +783,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> if (signal_pending(current)) {
> ret = -EINTR;
> run->exit_reason = KVM_EXIT_INTR;
> + ++vcpu->stat.signal_exits;
> }
>
> /*
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 1dfb83578277..50fc16ad872f 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -50,7 +50,8 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
> STATS_DESC_COUNTER(VCPU, wfi_exit_stat),
> STATS_DESC_COUNTER(VCPU, mmio_exit_user),
> STATS_DESC_COUNTER(VCPU, mmio_exit_kernel),
> - STATS_DESC_COUNTER(VCPU, exits)
> + STATS_DESC_COUNTER(VCPU, exits),
> + STATS_DESC_COUNTER(VCPU, signal_exits),
How about put signal_exits before exits as the same order in
kvm_vcpu_stat just for readability?
> };
> static_assert(ARRAY_SIZE(kvm_vcpu_stats_desc) ==
> sizeof(struct kvm_vcpu_stat) / sizeof(u64));
> --
> 2.32.0.554.ge1b32706d8-goog
>
Reviewed-by: Jing Zhang <[email protected]>
Thanks,
Jing
On Thu, Jul 29, 2021 at 1:07 PM Jing Zhang <[email protected]> wrote:
>
> On Thu, Jul 29, 2021 at 12:56 PM Oliver Upton <[email protected]> wrote:
> >
> > Most other architectures that implement KVM record a statistic
> > indicating the number of times a vCPU has exited due to a pending
> > signal. Add support for that stat to arm64.
> >
> > Cc: Jing Zhang <[email protected]>
> > Signed-off-by: Oliver Upton <[email protected]>
> > ---
> > arch/arm64/include/asm/kvm_host.h | 1 +
> > arch/arm64/kvm/arm.c | 1 +
> > arch/arm64/kvm/guest.c | 3 ++-
> > 3 files changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > index 41911585ae0c..70e129f2b574 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -576,6 +576,7 @@ struct kvm_vcpu_stat {
> > u64 wfi_exit_stat;
> > u64 mmio_exit_user;
> > u64 mmio_exit_kernel;
> > + u64 signal_exits;
> > u64 exits;
> > };
> >
> > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> > index e9a2b8f27792..60d0a546d7fd 100644
> > --- a/arch/arm64/kvm/arm.c
> > +++ b/arch/arm64/kvm/arm.c
> > @@ -783,6 +783,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> > if (signal_pending(current)) {
> > ret = -EINTR;
> > run->exit_reason = KVM_EXIT_INTR;
> > + ++vcpu->stat.signal_exits;
> > }
> >
> > /*
> > diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> > index 1dfb83578277..50fc16ad872f 100644
> > --- a/arch/arm64/kvm/guest.c
> > +++ b/arch/arm64/kvm/guest.c
> > @@ -50,7 +50,8 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
> > STATS_DESC_COUNTER(VCPU, wfi_exit_stat),
> > STATS_DESC_COUNTER(VCPU, mmio_exit_user),
> > STATS_DESC_COUNTER(VCPU, mmio_exit_kernel),
> > - STATS_DESC_COUNTER(VCPU, exits)
> > + STATS_DESC_COUNTER(VCPU, exits),
> > + STATS_DESC_COUNTER(VCPU, signal_exits),
> How about put signal_exits before exits as the same order in
> kvm_vcpu_stat just for readability?
Definitely.
> > };
> > static_assert(ARRAY_SIZE(kvm_vcpu_stats_desc) ==
> > sizeof(struct kvm_vcpu_stat) / sizeof(u64));
> > --
> > 2.32.0.554.ge1b32706d8-goog
> >
> Reviewed-by: Jing Zhang <[email protected]>
Thanks Jing!