2023-09-14 09:46:46

by Yang Weijiang

Subject: [PATCH v6 13/25] KVM: x86: Initialize kvm_caps.supported_xss

Set original kvm_caps.supported_xss to (host_xss & KVM_SUPPORTED_XSS) if
XSAVES is supported. host_xss contains the host supported xstate feature
bits for thread FPU context switch, KVM_SUPPORTED_XSS includes all KVM
enabled XSS feature bits, the resulting value represents the supervisor
xstates that are available to guest and are backed by host FPU framework
for swapping {guest,host} XSAVE-managed registers/MSRs.

Signed-off-by: Yang Weijiang <[email protected]>
---
arch/x86/kvm/x86.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9a616d84bd39..66edbed25db8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -226,6 +226,8 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
| XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)

+#define KVM_SUPPORTED_XSS 0
+
u64 __read_mostly host_efer;
EXPORT_SYMBOL_GPL(host_efer);

@@ -9515,12 +9517,13 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
kvm_caps.supported_xcr0 = host_xcr0 & KVM_SUPPORTED_XCR0;
}
+ if (boot_cpu_has(X86_FEATURE_XSAVES)) {
+ rdmsrl(MSR_IA32_XSS, host_xss);
+ kvm_caps.supported_xss = host_xss & KVM_SUPPORTED_XSS;
+ }

rdmsrl_safe(MSR_EFER, &host_efer);

- if (boot_cpu_has(X86_FEATURE_XSAVES))
- rdmsrl(MSR_IA32_XSS, host_xss);
-
kvm_init_pmu_capability(ops->pmu_ops);

if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
--
2.27.0

2023-10-31 17:52:21

by Maxim Levitsky

Subject: Re: [PATCH v6 13/25] KVM: x86: Initialize kvm_caps.supported_xss

On Thu, 2023-09-14 at 02:33 -0400, Yang Weijiang wrote:
> Set original kvm_caps.supported_xss to (host_xss & KVM_SUPPORTED_XSS) if
> XSAVES is supported. host_xss contains the host supported xstate feature
> bits for thread FPU context switch, KVM_SUPPORTED_XSS includes all KVM
> enabled XSS feature bits, the resulting value represents the supervisor
> xstates that are available to guest and are backed by host FPU framework
> for swapping {guest,host} XSAVE-managed registers/MSRs.
>
> Signed-off-by: Yang Weijiang <[email protected]>
> ---
> arch/x86/kvm/x86.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9a616d84bd39..66edbed25db8 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -226,6 +226,8 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
> | XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
> | XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)
>
> +#define KVM_SUPPORTED_XSS 0
> +
> u64 __read_mostly host_efer;
> EXPORT_SYMBOL_GPL(host_efer);
>
> @@ -9515,12 +9517,13 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
> host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
> kvm_caps.supported_xcr0 = host_xcr0 & KVM_SUPPORTED_XCR0;
> }
> + if (boot_cpu_has(X86_FEATURE_XSAVES)) {
> + rdmsrl(MSR_IA32_XSS, host_xss);
> + kvm_caps.supported_xss = host_xss & KVM_SUPPORTED_XSS;
> + }
>
> rdmsrl_safe(MSR_EFER, &host_efer);
>
> - if (boot_cpu_has(X86_FEATURE_XSAVES))
> - rdmsrl(MSR_IA32_XSS, host_xss);
> -
> kvm_init_pmu_capability(ops->pmu_ops);
>
> if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))


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

Best regards,
Maxim Levitsky