2022-11-03 14:29:10

by Maxim Levitsky

Subject: [PATCH v2 7/9] KVM: x86: allow L1 to not intercept triple fault

This is SVM correctness fix - although a sane L1 would intercept
SHUTDOWN event, it doesn't have to, so we have to honour this.

Signed-off-by: Maxim Levitsky <[email protected]>
---
arch/x86/kvm/svm/nested.c | 6 ++++++
arch/x86/kvm/vmx/nested.c | 1 +
arch/x86/kvm/x86.c | 11 ++++++-----
3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index bcc4f6620f8aec..3aa9184d1e4ed7 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1092,6 +1092,12 @@ int nested_svm_vmexit(struct vcpu_svm *svm)

static void nested_svm_triple_fault(struct kvm_vcpu *vcpu)
{
+ struct vcpu_svm *svm = to_svm(vcpu);
+
+ if (!vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SHUTDOWN))
+ return;
+
+ kvm_clear_request(KVM_REQ_TRIPLE_FAULT, vcpu);
nested_svm_simple_vmexit(to_svm(vcpu), SVM_EXIT_SHUTDOWN);
}

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 1ebe141a0a015f..7924dea9367813 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4855,6 +4855,7 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,

static void nested_vmx_triple_fault(struct kvm_vcpu *vcpu)
{
+ kvm_clear_request(KVM_REQ_TRIPLE_FAULT, vcpu);
nested_vmx_vmexit(vcpu, EXIT_REASON_TRIPLE_FAULT, 0, 0);
}

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3fd900504e683b..f0a0102a78f5c3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9741,7 +9741,7 @@ static void update_cr8_intercept(struct kvm_vcpu *vcpu)

int kvm_check_nested_events(struct kvm_vcpu *vcpu)
{
- if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
+ if (kvm_test_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
kvm_x86_ops.nested_ops->triple_fault(vcpu);
return 1;
}
@@ -10255,15 +10255,16 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
r = 0;
goto out;
}
- if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
- if (is_guest_mode(vcpu)) {
+ if (kvm_test_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
+ if (is_guest_mode(vcpu))
kvm_x86_ops.nested_ops->triple_fault(vcpu);
- } else {
+
+ if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
vcpu->mmio_needed = 0;
r = 0;
- goto out;
}
+ goto out;
}
if (kvm_check_request(KVM_REQ_APF_HALT, vcpu)) {
/* Page is swapped out. Do synthetic halt */
--
2.34.3

2022-11-21 16:38:25

by Liam Merwick

Subject: Re: [PATCH v2 7/9] KVM: x86: allow L1 to not intercept triple fault

On 03/11/2022 14:13, Maxim Levitsky wrote:
> This is SVM correctness fix - although a sane L1 would intercept
> SHUTDOWN event, it doesn't have to, so we have to honour this.
>
> Signed-off-by: Maxim Levitsky <[email protected]>
> ---
> arch/x86/kvm/svm/nested.c | 6 ++++++
> arch/x86/kvm/vmx/nested.c | 1 +
> arch/x86/kvm/x86.c | 11 ++++++-----
> 3 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index bcc4f6620f8aec..3aa9184d1e4ed7 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -1092,6 +1092,12 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
>
> static void nested_svm_triple_fault(struct kvm_vcpu *vcpu)
> {
> + struct vcpu_svm *svm = to_svm(vcpu);
> +
> + if (!vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SHUTDOWN))
> + return;
> +
> + kvm_clear_request(KVM_REQ_TRIPLE_FAULT, vcpu);
> nested_svm_simple_vmexit(to_svm(vcpu), SVM_EXIT_SHUTDOWN);

You could replace 'to_svm(vcpu)' with 'svm' here
But LGTM either way.

Reviewed-by: Liam Merwick <[email protected]>


> }
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 1ebe141a0a015f..7924dea9367813 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -4855,6 +4855,7 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
>
> static void nested_vmx_triple_fault(struct kvm_vcpu *vcpu)
> {
> + kvm_clear_request(KVM_REQ_TRIPLE_FAULT, vcpu);
> nested_vmx_vmexit(vcpu, EXIT_REASON_TRIPLE_FAULT, 0, 0);
> }
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3fd900504e683b..f0a0102a78f5c3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9741,7 +9741,7 @@ static void update_cr8_intercept(struct kvm_vcpu *vcpu)
>
> int kvm_check_nested_events(struct kvm_vcpu *vcpu)
> {
> - if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
> + if (kvm_test_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
> kvm_x86_ops.nested_ops->triple_fault(vcpu);
> return 1;
> }
> @@ -10255,15 +10255,16 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> r = 0;
> goto out;
> }
> - if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
> - if (is_guest_mode(vcpu)) {
> + if (kvm_test_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
> + if (is_guest_mode(vcpu))
> kvm_x86_ops.nested_ops->triple_fault(vcpu);
> - } else {
> +
> + if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
> vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
> vcpu->mmio_needed = 0;
> r = 0;
> - goto out;
> }
> + goto out;
> }
> if (kvm_check_request(KVM_REQ_APF_HALT, vcpu)) {
> /* Page is swapped out. Do synthetic halt */