Messages in this thread | | | Date | Wed, 9 Aug 2023 17:00:51 +0800 | Subject | Re: [PATCH v5 15/19] KVM:x86: Optimize CET supervisor SSP save/reload | From | "Yang, Weijiang" <> |
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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!
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