Messages in this thread | | | Date | Tue, 18 Jan 2022 17:17:01 +0100 | Subject | Re: [PATCH v2 0/4] KVM: x86: Partially allow KVM_SET_CPUID{,2} after KVM_RUN for CPU hotplug | From | Paolo Bonzini <> |
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On 1/18/22 15:35, Igor Mammedov wrote: > Can you check following scenario: > * on host that has IA32_TSX_CTRL and TSX enabled (RTM/HLE cpuid bits present) > * boot 2 vcpus VM with TSX enabled on VMM side but with tsx=off on kernel CLI > > that should cause kernel to set MSR_IA32_TSX_CTRL to 3H from initial 0H > and clear RTM+HLE bits in CPUID, check that RTM/HLE cpuid it cleared > > * hotunplug a VCPU and then replug it again > if IA32_TSX_CTRL is reset to initial state, that should re-enable > RTM/HLE cpuid bits and KVM_SET_CPUID2 might fail due to difference > > and as Sean pointed out there might be other non constant leafs, > where exact match check could leave userspace broken.
MSR_IA32_TSX_CTRL is handled differently straight during the CPUID call:
if (function == 7 && index == 0) { u64 data; if (!__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) && (data & TSX_CTRL_CPUID_CLEAR)) *ebx &= ~(F(RTM) | F(HLE)); }
and I think we should redo all or most of kvm_update_cpuid_runtime the same way.
Paolo
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