[PATCH v3] KVM: x86: Sync the states size with the XCR0/IA32_XSS at, any time

[Like Xu]

From: Like Xu <likexu@xxxxxxxxxxx>

XCR0 is reset to 1 by RESET but not INIT and IA32_XSS is zeroed by
both RESET and INIT. The kvm_set_msr_common()'s handling of MSR_IA32_XSS
also needs to update kvm_update_cpuid_runtime(). In the above cases, the
size in bytes of the XSAVE area containing all states enabled by XCR0 or
(XCRO | IA32_XSS) needs to be updated.

For simplicity and consistency, existing helpers are used to write values
and call kvm_update_cpuid_runtime(), and it's not exactly a fast path.

Fixes: a554d207dc46 ("KVM: X86: Processor States following Reset or INIT")
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
v2 -> v3 Changelog:
- Apply s/legacy/existing in the commit message; (Sean)
- Invoke kvm_update_cpuid_runtime() for MSR_IA32_XSS; (Sean)

 arch/x86/kvm/x86.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 55518b7d3b96..4b509b26d9ab 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3535,6 +3535,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct 
msr_data *msr_info)
 		if (data & ~supported_xss)
 			return 1;
 		vcpu->arch.ia32_xss = data;
+		kvm_update_cpuid_runtime(vcpu);
 		break;
 	case MSR_SMI_COUNT:
 		if (!msr_info->host_initiated)
@@ -11256,7 +11257,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)

 		vcpu->arch.msr_misc_features_enables = 0;

-		vcpu->arch.xcr0 = XFEATURE_MASK_FP;
+		__kvm_set_xcr(vcpu, 0, XFEATURE_MASK_FP);
 	}

 	/* All GPRs except RDX (handled below) are zeroed on RESET/INIT. */
@@ -11273,7 +11274,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	cpuid_0x1 = kvm_find_cpuid_entry(vcpu, 1, 0);
 	kvm_rdx_write(vcpu, cpuid_0x1 ? cpuid_0x1->eax : 0x600);

-	vcpu->arch.ia32_xss = 0;
+	__kvm_set_msr(vcpu, MSR_IA32_XSS, 0, true);

 	static_call(kvm_x86_vcpu_reset)(vcpu, init_event);

--
2.33.1