2024-03-09 01:38:09

by Sean Christopherson

Subject: [PATCH v6 3/9] KVM: x86: Stuff vCPU's PAT with default value at RESET, not creation

Move the stuffing of the vCPU's PAT to the architectural "default" value
from kvm_arch_vcpu_create() to kvm_vcpu_reset(), guarded by !init_event,
to better capture that the default value is the value "Following Power-up
or Reset". E.g. setting PAT only during creation would break if KVM were
to expose a RESET ioctl() to userspace (which is unlikely, but that's not
a good reason to have unintuitive code).

No functional change.

Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/x86.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 66c4381460dc..eac97b1b8379 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12134,8 +12134,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu);

- vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;
-
kvm_async_pf_hash_reset(vcpu);

vcpu->arch.perf_capabilities = kvm_caps.supported_perf_cap;
@@ -12302,6 +12300,8 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
if (!init_event) {
vcpu->arch.smbase = 0x30000;

+ vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;
+
vcpu->arch.msr_misc_features_enables = 0;
vcpu->arch.ia32_misc_enable_msr = MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL |
MSR_IA32_MISC_ENABLE_BTS_UNAVAIL;
--
2.44.0.278.ge034bb2e1d-goog

2024-03-27 11:23:09

by Huang, Kai

Subject: Re: [PATCH v6 3/9] KVM: x86: Stuff vCPU's PAT with default value at RESET, not creation

On Fri, 2024-03-08 at 17:27 -0800, Sean Christopherson wrote:
> Move the stuffing of the vCPU's PAT to the architectural "default" value
> from kvm_arch_vcpu_create() to kvm_vcpu_reset(), guarded by !init_event,
> to better capture that the default value is the value "Following Power-up
> or Reset". E.g. setting PAT only during creation would break if KVM were
> to expose a RESET ioctl() to userspace (which is unlikely, but that's not
> a good reason to have unintuitive code).
>
> No functional change.
>
> Signed-off-by: Sean Christopherson <[email protected]>
>

Reviewed-by: Kai Huang <[email protected]>

2024-04-01 06:01:10

by Xiaoyao Li

Subject: Re: [PATCH v6 3/9] KVM: x86: Stuff vCPU's PAT with default value at RESET, not creation

On 3/9/2024 9:27 AM, Sean Christopherson wrote:
> Move the stuffing of the vCPU's PAT to the architectural "default" value
> from kvm_arch_vcpu_create() to kvm_vcpu_reset(), guarded by !init_event,
> to better capture that the default value is the value "Following Power-up
> or Reset". E.g. setting PAT only during creation would break if KVM were
> to expose a RESET ioctl() to userspace (which is unlikely, but that's not
> a good reason to have unintuitive code).
>
> No functional change.
>
> Signed-off-by: Sean Christopherson <[email protected]>

Reviewed-by: Xiaoyao Li <[email protected]>

> ---
> arch/x86/kvm/x86.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 66c4381460dc..eac97b1b8379 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12134,8 +12134,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
> vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
> vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu);
>
> - vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;
> -
> kvm_async_pf_hash_reset(vcpu);
>
> vcpu->arch.perf_capabilities = kvm_caps.supported_perf_cap;
> @@ -12302,6 +12300,8 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
> if (!init_event) {
> vcpu->arch.smbase = 0x30000;
>
> + vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;
> +
> vcpu->arch.msr_misc_features_enables = 0;
> vcpu->arch.ia32_misc_enable_msr = MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL |
> MSR_IA32_MISC_ENABLE_BTS_UNAVAIL;