On 8/4/2023 4:43 PM, Chao Gao wrote:
On Thu, Aug 03, 2023 at 12:27:28AM -0400, Yang Weijiang wrote:Make PL{0,1,2}_SSP as write-intercepted to detect whether guest is using these MSRs. Disable intercept to the MSRs if they're written with non-zero values. KVM does save/ reload for the MSRs only if they're used by guest.What would happen if guest tries to use XRSTORS to load S_CET state from a xsave area without any writes to the PL0-2_SSP (i.e., at that point, writes to the MSRs are still intercepted)?
I need to do some experiments to get the details, but now expect some kind of error in guest is seen.
@@ -2420,6 +2432,14 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) else vmx->pt_desc.guest.addr_a[index / 2] = data; break; + case MSR_IA32_PL0_SSP ... MSR_IA32_PL2_SSP: + if (kvm_set_msr_common(vcpu, msr_info)) + return 1; + if (data) { + vmx_disable_write_intercept_sss_msr(vcpu); + wrmsrl(msr_index, data);Is it necessary to do the wrmsl()? looks the next kvm_x86_prepare_switch_to_guest() will load PL0-2_SSP from the caching values.
Oh, yes, it's not necessary after moving the reload logic to kvm_x86_prepare_switch_to_guest(). Thanks!
