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Subject[PATCH v11 5/9] KVM: X86: Refresh CPUID once guest XSS MSR changes
Date
CPUID(0xd, 1) reports the current required storage size of
XCR0 | XSS, when guest updates the XSS, it's necessary to update
the CPUID leaf, otherwise guest will fetch old state size, and
results to some WARN traces during guest running.

Co-developed-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/cpuid.c | 21 ++++++++++++++++++---
arch/x86/kvm/x86.c | 9 +++++++--
3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 24c90ea5ddbd..2c944ad99692 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -650,6 +650,7 @@ struct kvm_vcpu_arch {

u64 xcr0;
u64 guest_supported_xcr0;
+ u64 guest_supported_xss;
u32 guest_xstate_size;

struct kvm_pio_request pio;
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 78d461be2102..25e9a11291b3 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -95,9 +95,24 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
}

best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
- if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
- cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
- best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
+ if (best) {
+ if (best->eax & (F(XSAVES) | F(XSAVEC))) {
+ u64 xstate = vcpu->arch.xcr0 | vcpu->arch.ia32_xss;
+
+ best->ebx = xstate_required_size(xstate, true);
+ }
+
+ if (best->eax & F(XSAVES)) {
+ vcpu->arch.guest_supported_xss =
+ (best->ecx | ((u64)best->edx << 32)) & supported_xss;
+ } else {
+ best->ecx = 0;
+ best->edx = 0;
+ vcpu->arch.guest_supported_xss = 0;
+ }
+ } else {
+ vcpu->arch.guest_supported_xss = 0;
+ }

/*
* The existing code assumes virtual address is 48-bit or 57-bit in the
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 90acdbbb8a5a..51ecb496d47d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2836,9 +2836,12 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
* IA32_XSS[bit 8]. Guests have to use RDMSR/WRMSR rather than
* XSAVES/XRSTORS to save/restore PT MSRs.
*/
- if (data & ~supported_xss)
+ if (data & ~vcpu->arch.guest_supported_xss)
return 1;
- vcpu->arch.ia32_xss = data;
+ if (vcpu->arch.ia32_xss != data) {
+ vcpu->arch.ia32_xss = data;
+ kvm_update_cpuid(vcpu);
+ }
break;
case MSR_SMI_COUNT:
if (!msr_info->host_initiated)
@@ -9635,6 +9638,8 @@ int kvm_arch_hardware_setup(void)

if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
supported_xss = 0;
+ else
+ supported_xss = host_xss & KVM_SUPPORTED_XSS;

cr4_reserved_bits = kvm_host_cr4_reserved_bits(&boot_cpu_data);

--
2.17.2
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