[PATCH v5 05/19] KVM:x86: Initialize kvm_caps.supported_xss

Yang Weijiang
2023-08-03T07:37:17Z

Set kvm_caps.supported_xss to host_xss && KVM XSS mask.
host_xss contains the host supported xstate feature bits for thread
context switch, KVM_SUPPORTED_XSS includes all KVM enabled XSS feature
bits, the operation result represents all KVM supported feature bits.
Since the result is subset of host_xss, the related XSAVE-managed MSRs
are automatically swapped for guest and host when vCPU exits to
userspace.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/kvm/vmx/vmx.c | 1 -
arch/x86/kvm/x86.c | 6 +++++-
2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 0ecf4be2c6af..c8d9870cfecb 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7849,7 +7849,6 @@ static __init void vmx_set_cpu_caps(void)
kvm_cpu_cap_set(X86_FEATURE_UMIP);

/* CPUID 0xD.1 */
- kvm_caps.supported_xss = 0;
if (!cpu_has_vmx_xsaves())
kvm_cpu_cap_clear(X86_FEATURE_XSAVES);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5d6d6fa33e5b..e9f3627d5fdd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -225,6 +225,8 @@ 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);

@@ -9498,8 +9500,10 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)

rdmsrl_safe(MSR_EFER, &host_efer);

- if (boot_cpu_has(X86_FEATURE_XSAVES))
+ if (boot_cpu_has(X86_FEATURE_XSAVES)) {
rdmsrl(MSR_IA32_XSS, host_xss);
+ kvm_caps.supported_xss = host_xss & KVM_SUPPORTED_XSS;
+ }

kvm_init_pmu_capability(ops->pmu_ops);

--
2.27.0