2021-05-05 19:49:00

by Vitaly Kuznetsov

Subject: [PATCH 0/3] KVM: selftests: evmcs_test: Check issues induced by late eVMCS mapping upon restore

A regression was introduced by commit f2c7ef3ba955
("KVM: nSVM: cancel KVM_REQ_GET_NESTED_STATE_PAGES on nested vmexit"). When
L2->L1 exit is forced immediately after restoring nested state,
KVM_REQ_GET_NESTED_STATE_PAGES request is cleared and VMCS12 changes (e.g.
fresh RIP) are not reflected to eVMCS. The consequent nested vCPU run gets
broken. Add a test for the condition (PATCH2). PATCH1 is a preparatory
change, PATCH3 adds a test for a situation when KVM_GET_NESTED_STATE is
requested right after KVM_SET_NESTED_STATE, this is still broken in KVM
(so the patch is not to be committed).

Vitaly Kuznetsov (3):
KVM: selftests: evmcs_test: Check that VMLAUNCH with bogus EVMPTR is
causing #UD
KVM: selftests: evmcs_test: Check that VMCS12 is alway properly synced
to eVMCS after restore
KVM: selftests: evmcs_test: Test that KVM_STATE_NESTED_EVMCS is never
lost

.../testing/selftests/kvm/x86_64/evmcs_test.c | 150 +++++++++++++-----
1 file changed, 108 insertions(+), 42 deletions(-)

--
2.30.2

2021-05-05 19:49:05

by Vitaly Kuznetsov

Subject: [PATCH 3/3] KVM: selftests: evmcs_test: Test that KVM_STATE_NESTED_EVMCS is never lost

Do KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE for a freshly restored VM
(before the first KVM_RUN) to check that KVM_STATE_NESTED_EVMCS is not
lost.

Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
- Note: this test is not yet to be commited as it is known to fail. A
patch like
https://lore.kernel.org/kvm/[email protected]/T/#u
is needed to make it pass. The patch itself requires more work.
---
.../testing/selftests/kvm/x86_64/evmcs_test.c | 62 ++++++++++++-------
1 file changed, 38 insertions(+), 24 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/evmcs_test.c b/tools/testing/selftests/kvm/x86_64/evmcs_test.c
index 63096cea26c6..8d1a63da5c63 100644
--- a/tools/testing/selftests/kvm/x86_64/evmcs_test.c
+++ b/tools/testing/selftests/kvm/x86_64/evmcs_test.c
@@ -121,14 +121,39 @@ void inject_nmi(struct kvm_vm *vm)
vcpu_events_set(vm, VCPU_ID, &events);
}

+static void save_restore_vm(struct kvm_vm *vm, struct kvm_run *run)
+{
+ struct kvm_regs regs1, regs2;
+ struct kvm_x86_state *state;
+
+ state = vcpu_save_state(vm, VCPU_ID);
+ memset(&regs1, 0, sizeof(regs1));
+ vcpu_regs_get(vm, VCPU_ID, &regs1);
+
+ kvm_vm_release(vm);
+
+ /* Restore state in a new VM. */
+ kvm_vm_restart(vm, O_RDWR);
+ vm_vcpu_add(vm, VCPU_ID);
+ vcpu_set_hv_cpuid(vm, VCPU_ID);
+ vcpu_enable_evmcs(vm, VCPU_ID);
+ vcpu_load_state(vm, VCPU_ID, state);
+ run = vcpu_state(vm, VCPU_ID);
+ free(state);
+
+ memset(&regs2, 0, sizeof(regs2));
+ vcpu_regs_get(vm, VCPU_ID, &regs2);
+ TEST_ASSERT(!memcmp(&regs1, &regs2, sizeof(regs2)),
+ "Unexpected register values after vcpu_load_state; rdi: %lx rsi: %lx",
+ (ulong) regs2.rdi, (ulong) regs2.rsi);
+}
+
int main(int argc, char *argv[])
{
vm_vaddr_t vmx_pages_gva = 0;

- struct kvm_regs regs1, regs2;
struct kvm_vm *vm;
struct kvm_run *run;
- struct kvm_x86_state *state;
struct ucall uc;
int stage;

@@ -147,8 +172,6 @@ int main(int argc, char *argv[])

run = vcpu_state(vm, VCPU_ID);

- vcpu_regs_get(vm, VCPU_ID, &regs1);
-
vcpu_alloc_vmx(vm, &vmx_pages_gva);
vcpu_args_set(vm, VCPU_ID, 1, vmx_pages_gva);

@@ -184,32 +207,23 @@ int main(int argc, char *argv[])
uc.args[1] == stage, "Stage %d: Unexpected register values vmexit, got %lx",
stage, (ulong)uc.args[1]);

- state = vcpu_save_state(vm, VCPU_ID);
- memset(&regs1, 0, sizeof(regs1));
- vcpu_regs_get(vm, VCPU_ID, &regs1);
-
- kvm_vm_release(vm);
-
- /* Restore state in a new VM. */
- kvm_vm_restart(vm, O_RDWR);
- vm_vcpu_add(vm, VCPU_ID);
- vcpu_set_hv_cpuid(vm, VCPU_ID);
- vcpu_enable_evmcs(vm, VCPU_ID);
- vcpu_load_state(vm, VCPU_ID, state);
- run = vcpu_state(vm, VCPU_ID);
- free(state);
-
- memset(&regs2, 0, sizeof(regs2));
- vcpu_regs_get(vm, VCPU_ID, &regs2);
- TEST_ASSERT(!memcmp(&regs1, &regs2, sizeof(regs2)),
- "Unexpected register values after vcpu_load_state; rdi: %lx rsi: %lx",
- (ulong) regs2.rdi, (ulong) regs2.rsi);
+ save_restore_vm(vm, run);

/* Force immediate L2->L1 exit before resuming */
if (stage == 8) {
pr_info("Injecting NMI into L1 before L2 had a chance to run after restore\n");
inject_nmi(vm);
}
+
+ /*
+ * Do KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE for a freshly
+ * restored VM (before the first KVM_RUN) to check that
+ * KVM_STATE_NESTED_EVMCS is not lost.
+ */
+ if (stage == 9) {
+ pr_info("Trying extra KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE cycle\n");
+ save_restore_vm(vm, run);
+ }
}

done:
--
2.30.2

2021-05-05 20:49:50

by Paolo Bonzini

Subject: Re: [PATCH 0/3] KVM: selftests: evmcs_test: Check issues induced by late eVMCS mapping upon restore

On 05/05/21 17:18, Vitaly Kuznetsov wrote:
> A regression was introduced by commit f2c7ef3ba955
> ("KVM: nSVM: cancel KVM_REQ_GET_NESTED_STATE_PAGES on nested vmexit"). When
> L2->L1 exit is forced immediately after restoring nested state,
> KVM_REQ_GET_NESTED_STATE_PAGES request is cleared and VMCS12 changes (e.g.
> fresh RIP) are not reflected to eVMCS. The consequent nested vCPU run gets
> broken. Add a test for the condition (PATCH2). PATCH1 is a preparatory
> change, PATCH3 adds a test for a situation when KVM_GET_NESTED_STATE is
> requested right after KVM_SET_NESTED_STATE, this is still broken in KVM
> (so the patch is not to be committed).
>
> Vitaly Kuznetsov (3):
> KVM: selftests: evmcs_test: Check that VMLAUNCH with bogus EVMPTR is
> causing #UD
> KVM: selftests: evmcs_test: Check that VMCS12 is alway properly synced
> to eVMCS after restore
> KVM: selftests: evmcs_test: Test that KVM_STATE_NESTED_EVMCS is never
> lost
>
> .../testing/selftests/kvm/x86_64/evmcs_test.c | 150 +++++++++++++-----
> 1 file changed, 108 insertions(+), 42 deletions(-)
>

Queued 1-2, thanks.

Paolo