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Subject[PATCH v9 5/7] KVM: X86: Enable CET bits update in IA32_XSS
Date
Previously, KVM did not support setting any bits in XSS
so it's hardcoded to check and inject a #GP if Guest
attempted to write a non-zero value to XSS, now it supports
CET related bits setting.

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 | 12 ++++++++++--
arch/x86/kvm/vmx/vmx.c | 6 +-----
3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4e59f17ded50..64bf379381e4 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -620,6 +620,7 @@ 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 546cfe123ba7..126a31b99823 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -125,8 +125,16 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
}

best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
- if (best && (best->eax & (F(XSAVES) | F(XSAVEC))))
- best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
+ if (best && (best->eax & (F(XSAVES) | F(XSAVEC)))) {
+ u64 xstate = vcpu->arch.xcr0 | vcpu->arch.ia32_xss;
+
+ best->ebx = xstate_required_size(xstate, true);
+ vcpu->arch.guest_supported_xss =
+ (best->ecx | ((u64)best->edx << 32)) &
+ kvm_supported_xss();
+ } 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/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 95063cc7da89..0a75b65d03f0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2081,11 +2081,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
!(guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&
guest_cpuid_has(vcpu, X86_FEATURE_XSAVES))))
return 1;
- /*
- * The only supported bit as of Skylake is bit 8, but
- * it is not supported on KVM.
- */
- if (data != 0)
+ if (data & ~vcpu->arch.guest_supported_xss)
return 1;
vcpu->arch.ia32_xss = data;
if (vcpu->arch.ia32_xss != host_xss)
--
2.17.2
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