* [PATCH v2] KVM: x86: Add a helper to dedup loading guest/host XCR0 and XSS
@ 2025-11-10 5:05 Binbin Wu
2025-11-10 12:54 ` Xiaoyao Li
2025-11-21 18:55 ` Sean Christopherson
0 siblings, 2 replies; 3+ messages in thread
From: Binbin Wu @ 2025-11-10 5:05 UTC (permalink / raw)
To: seanjc, pbonzini; +Cc: kvm, linux-kernel, chao.gao, xiaoyao.li, binbin.wu
Add and use a helper, kvm_load_xfeatures(), to dedup the code that loads
guest/host xfeatures.
Opportunistically return early if X86_CR4_OSXSAVE is not set to reduce
indentations.
No functional change intended.
Suggested-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
---
v2:
- Pass a bool to distinguish guest/host. [Chao, Xiaoyao]
- Fix a typo in the short log. [Chao]
- Opportunistically return early if X86_CR4_OSXSAVE is not set to reduce
indentations.
v1:
- https://lore.kernel.org/kvm/20251106101138.2756175-1-binbin.wu@linux.intel.com
---
arch/x86/kvm/x86.c | 33 ++++++++++-----------------------
1 file changed, 10 insertions(+), 23 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9c2e28028c2b..2c521902e2c6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1219,34 +1219,21 @@ void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw)
}
EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_lmsw);
-static void kvm_load_guest_xfeatures(struct kvm_vcpu *vcpu)
+static void kvm_load_xfeatures(struct kvm_vcpu *vcpu, bool load_guest)
{
if (vcpu->arch.guest_state_protected)
return;
- if (kvm_is_cr4_bit_set(vcpu, X86_CR4_OSXSAVE)) {
- if (vcpu->arch.xcr0 != kvm_host.xcr0)
- xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
-
- if (guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVES) &&
- vcpu->arch.ia32_xss != kvm_host.xss)
- wrmsrq(MSR_IA32_XSS, vcpu->arch.ia32_xss);
- }
-}
-
-static void kvm_load_host_xfeatures(struct kvm_vcpu *vcpu)
-{
- if (vcpu->arch.guest_state_protected)
+ if (!kvm_is_cr4_bit_set(vcpu, X86_CR4_OSXSAVE))
return;
- if (kvm_is_cr4_bit_set(vcpu, X86_CR4_OSXSAVE)) {
- if (vcpu->arch.xcr0 != kvm_host.xcr0)
- xsetbv(XCR_XFEATURE_ENABLED_MASK, kvm_host.xcr0);
+ if (vcpu->arch.xcr0 != kvm_host.xcr0)
+ xsetbv(XCR_XFEATURE_ENABLED_MASK,
+ load_guest ? vcpu->arch.xcr0 : kvm_host.xcr0);
- if (guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVES) &&
- vcpu->arch.ia32_xss != kvm_host.xss)
- wrmsrq(MSR_IA32_XSS, kvm_host.xss);
- }
+ if (guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVES) &&
+ vcpu->arch.ia32_xss != kvm_host.xss)
+ wrmsrq(MSR_IA32_XSS, load_guest ? vcpu->arch.ia32_xss : kvm_host.xss);
}
static void kvm_load_guest_pkru(struct kvm_vcpu *vcpu)
@@ -11333,7 +11320,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
if (vcpu->arch.guest_fpu.xfd_err)
wrmsrq(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
- kvm_load_guest_xfeatures(vcpu);
+ kvm_load_xfeatures(vcpu, true);
if (unlikely(vcpu->arch.switch_db_regs &&
!(vcpu->arch.switch_db_regs & KVM_DEBUGREG_AUTO_SWITCH))) {
@@ -11429,7 +11416,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
vcpu->mode = OUTSIDE_GUEST_MODE;
smp_wmb();
- kvm_load_host_xfeatures(vcpu);
+ kvm_load_xfeatures(vcpu, false);
/*
* Sync xfd before calling handle_exit_irqoff() which may
base-commit: 9052f4f6c539ea1fb7b282a34e6bb33154ce0b63
--
2.46.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] KVM: x86: Add a helper to dedup loading guest/host XCR0 and XSS
2025-11-10 5:05 [PATCH v2] KVM: x86: Add a helper to dedup loading guest/host XCR0 and XSS Binbin Wu
@ 2025-11-10 12:54 ` Xiaoyao Li
2025-11-21 18:55 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: Xiaoyao Li @ 2025-11-10 12:54 UTC (permalink / raw)
To: Binbin Wu, seanjc, pbonzini; +Cc: kvm, linux-kernel, chao.gao
On 11/10/2025 1:05 PM, Binbin Wu wrote:
> Add and use a helper, kvm_load_xfeatures(), to dedup the code that loads
> guest/host xfeatures.
>
> Opportunistically return early if X86_CR4_OSXSAVE is not set to reduce
> indentations.
>
> No functional change intended.
>
> Suggested-by: Chao Gao <chao.gao@intel.com>
> Reviewed-by: Chao Gao <chao.gao@intel.com>
> Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
> v2:
> - Pass a bool to distinguish guest/host. [Chao, Xiaoyao]
> - Fix a typo in the short log. [Chao]
> - Opportunistically return early if X86_CR4_OSXSAVE is not set to reduce
> indentations.
>
> v1:
> - https://lore.kernel.org/kvm/20251106101138.2756175-1-binbin.wu@linux.intel.com
> ---
> arch/x86/kvm/x86.c | 33 ++++++++++-----------------------
> 1 file changed, 10 insertions(+), 23 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9c2e28028c2b..2c521902e2c6 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1219,34 +1219,21 @@ void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw)
> }
> EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_lmsw);
>
> -static void kvm_load_guest_xfeatures(struct kvm_vcpu *vcpu)
> +static void kvm_load_xfeatures(struct kvm_vcpu *vcpu, bool load_guest)
> {
> if (vcpu->arch.guest_state_protected)
> return;
>
> - if (kvm_is_cr4_bit_set(vcpu, X86_CR4_OSXSAVE)) {
> - if (vcpu->arch.xcr0 != kvm_host.xcr0)
> - xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
> -
> - if (guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVES) &&
> - vcpu->arch.ia32_xss != kvm_host.xss)
> - wrmsrq(MSR_IA32_XSS, vcpu->arch.ia32_xss);
> - }
> -}
> -
> -static void kvm_load_host_xfeatures(struct kvm_vcpu *vcpu)
> -{
> - if (vcpu->arch.guest_state_protected)
> + if (!kvm_is_cr4_bit_set(vcpu, X86_CR4_OSXSAVE))
> return;
>
> - if (kvm_is_cr4_bit_set(vcpu, X86_CR4_OSXSAVE)) {
> - if (vcpu->arch.xcr0 != kvm_host.xcr0)
> - xsetbv(XCR_XFEATURE_ENABLED_MASK, kvm_host.xcr0);
> + if (vcpu->arch.xcr0 != kvm_host.xcr0)
> + xsetbv(XCR_XFEATURE_ENABLED_MASK,
> + load_guest ? vcpu->arch.xcr0 : kvm_host.xcr0);
>
> - if (guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVES) &&
> - vcpu->arch.ia32_xss != kvm_host.xss)
> - wrmsrq(MSR_IA32_XSS, kvm_host.xss);
> - }
> + if (guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVES) &&
> + vcpu->arch.ia32_xss != kvm_host.xss)
> + wrmsrq(MSR_IA32_XSS, load_guest ? vcpu->arch.ia32_xss : kvm_host.xss);
> }
>
> static void kvm_load_guest_pkru(struct kvm_vcpu *vcpu)
> @@ -11333,7 +11320,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> if (vcpu->arch.guest_fpu.xfd_err)
> wrmsrq(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
>
> - kvm_load_guest_xfeatures(vcpu);
> + kvm_load_xfeatures(vcpu, true);
>
> if (unlikely(vcpu->arch.switch_db_regs &&
> !(vcpu->arch.switch_db_regs & KVM_DEBUGREG_AUTO_SWITCH))) {
> @@ -11429,7 +11416,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> vcpu->mode = OUTSIDE_GUEST_MODE;
> smp_wmb();
>
> - kvm_load_host_xfeatures(vcpu);
> + kvm_load_xfeatures(vcpu, false);
>
> /*
> * Sync xfd before calling handle_exit_irqoff() which may
>
> base-commit: 9052f4f6c539ea1fb7b282a34e6bb33154ce0b63
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] KVM: x86: Add a helper to dedup loading guest/host XCR0 and XSS
2025-11-10 5:05 [PATCH v2] KVM: x86: Add a helper to dedup loading guest/host XCR0 and XSS Binbin Wu
2025-11-10 12:54 ` Xiaoyao Li
@ 2025-11-21 18:55 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: Sean Christopherson @ 2025-11-21 18:55 UTC (permalink / raw)
To: Sean Christopherson, pbonzini, Binbin Wu
Cc: kvm, linux-kernel, chao.gao, xiaoyao.li
On Mon, 10 Nov 2025 13:05:39 +0800, Binbin Wu wrote:
> Add and use a helper, kvm_load_xfeatures(), to dedup the code that loads
> guest/host xfeatures.
>
> Opportunistically return early if X86_CR4_OSXSAVE is not set to reduce
> indentations.
>
> No functional change intended.
>
> [...]
Applied to kvm-x86 misc, thanks!
[1/1] KVM: x86: Add a helper to dedup loading guest/host XCR0 and XSS
https://github.com/kvm-x86/linux/commit/0b28f21ad462
--
https://github.com/kvm-x86/linux/tree/next
^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-11-10 12:54 ` Xiaoyao Li
2025-11-21 18:55 ` Sean Christopherson
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