2022-10-01 01:17:39

by Sean Christopherson

Subject: [PATCH v4 31/32] Revert "KVM: SVM: Do not throw warning when calling avic_vcpu_load on a running vcpu"

Turns out that some warnings exist for good reasons. Restore the warning
in avic_vcpu_load() that guards against calling avic_vcpu_load() on a
running vCPU now that KVM avoids doing so when switching between x2APIC
and xAPIC. The entire point of the WARN is to highlight that KVM should
not be reloading an AVIC.

Opportunistically convert the WARN_ON() to WARN_ON_ONCE() to avoid
spamming the kernel if it does fire.

This reverts commit c0caeee65af3944b7b8abbf566e7cc1fae15c775.

Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/svm/avic.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 953b1fd14b6d..35b0ef877e53 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -1038,6 +1038,7 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
return;

entry = READ_ONCE(*(svm->avic_physical_id_cache));
+ WARN_ON_ONCE(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK);

entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK;
entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK);
--
2.38.0.rc1.362.ged0d419d3c-goog

2022-12-08 22:40:33

by Maxim Levitsky

Subject: Re: [PATCH v4 31/32] Revert "KVM: SVM: Do not throw warning when calling avic_vcpu_load on a running vcpu"

On Sat, 2022-10-01 at 00:59 +0000, Sean Christopherson wrote:
> Turns out that some warnings exist for good reasons. Restore the warning
> in avic_vcpu_load() that guards against calling avic_vcpu_load() on a
> running vCPU now that KVM avoids doing so when switching between x2APIC
> and xAPIC. The entire point of the WARN is to highlight that KVM should
> not be reloading an AVIC.
>
> Opportunistically convert the WARN_ON() to WARN_ON_ONCE() to avoid
> spamming the kernel if it does fire.
>
> This reverts commit c0caeee65af3944b7b8abbf566e7cc1fae15c775.
>
> Signed-off-by: Sean Christopherson <[email protected]>
> ---
> arch/x86/kvm/svm/avic.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 953b1fd14b6d..35b0ef877e53 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -1038,6 +1038,7 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> return;
>
> entry = READ_ONCE(*(svm->avic_physical_id_cache));
> + WARN_ON_ONCE(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK);
>
> entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK;
> entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK);


Reviewed-by: Maxim Levitsky <[email protected]>


Best regards,
Maxim Levitsky