When running as an SEV-ES guest, the PL0_SSP, PL1_SSP, PL2_SSP, PL3_SSP,
and U_CET fields in the VMCB save area are type B, meaning the host
state is automatically loaded on a VMEXIT, but is not saved on a VMRUN.
The other shadow stack MSRs, S_CET, SSP, and ISST_ADDR are type A,
meaning they are loaded on VMEXIT and saved on VMRUN. PL0_SSP, PL1_SSP,
and PL2_SSP are currently unused. Manually save the other type B host
MSR values before VMRUN.
Signed-off-by: John Allen <john.allen@xxxxxxx>
---
v3:
- Don't save unused PL0_SSP, PL1_SSP, and PL2_SSP MSRs.
---
arch/x86/kvm/svm/sev.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 2cd15783dfb9..021ead4dd201 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3097,6 +3097,15 @@ void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa)
hostsa->dr2_addr_mask = amd_get_dr_addr_mask(2);
hostsa->dr3_addr_mask = amd_get_dr_addr_mask(3);
}
+
+ if (boot_cpu_has(X86_FEATURE_SHSTK)) {
+ /*
+ * MSR_IA32_U_CET and MSR_IA32_PL3_SSP are restored on VMEXIT,
+ * save the current host values.
+ */
+ rdmsrl(MSR_IA32_U_CET, hostsa->u_cet);
+ rdmsrl(MSR_IA32_PL3_SSP, hostsa->pl3_ssp);
+ }
}
void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector)
--
2.39.1
