On 5/23/2023 4:57 PM, Binbin Wu wrote:
On 5/11/2023 12:08 PM, Yang Weijiang wrote:
Introduce a host-only synthetic MSR, MSR_KVM_GUEST_SSP, so that the VMM
can read/write the guest's SSP, e.g. to migrate CET state. Use a
synthetic
MSR, e.g. as opposed to a VCPU_REG_, as GUEST_SSP is subject to the same
consistency checks as the PL*_SSP MSRs, i.e. can share code.
Co-developed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
arch/x86/include/uapi/asm/kvm_para.h | 1 +
arch/x86/kvm/vmx/vmx.c | 15 ++++++++++++---
arch/x86/kvm/x86.c | 4 ++++
3 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/uapi/asm/kvm_para.h
b/arch/x86/include/uapi/asm/kvm_para.h
index 6e64b27b2c1e..7af465e4e0bd 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -58,6 +58,7 @@
#define MSR_KVM_ASYNC_PF_INT 0x4b564d06
#define MSR_KVM_ASYNC_PF_ACK 0x4b564d07
#define MSR_KVM_MIGRATION_CONTROL 0x4b564d08
+#define MSR_KVM_GUEST_SSP 0x4b564d09
struct kvm_steal_time {
__u64 steal;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 0ccaa467d7d3..72149156bbd3 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2095,9 +2095,13 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu,
struct msr_data *msr_info)
break;
case MSR_IA32_U_CET:
case MSR_IA32_PL3_SSP:
+ case MSR_KVM_GUEST_SSP:
if (!kvm_cet_is_msr_accessible(vcpu, msr_info))
return 1;
- kvm_get_xsave_msr(msr_info);
+ if (msr_info->index == MSR_KVM_GUEST_SSP)
+ msr_info->data = vmcs_readl(GUEST_SSP);
According to the change of the kvm_cet_is_msr_accessible() below,
kvm_cet_is_msr_accessible() will return false for MSR_KVM_GUEST_SSP,
then this code is unreachable?
No, when the access is initiated from host side,
kvm_cet_is_msr_accessible() return true for MSR_KVM_GUEST_SSP.
So the code is reachable:
if (msr->host_initiated)
return true;
[...]
