Messages in this thread | | | Subject | Re: [PATCH] kvm/x86/vmx: switch MSR_MISC_FEATURES_ENABLES between host and guest | From | Paolo Bonzini <> | Date | Thu, 14 Mar 2019 15:44:39 +0100 |
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On 14/03/19 13:37, Xiaoyao Li wrote: >> Adding a RDMSR for this to each vmentry is too heavy. Since we emulate >> MSR_MISC_FEATURES_ENABLES, you can just clear the MSR on vcpu_load and >> restore it on vcpu_put. > One question here. Just clear the MSR on vcpu_load instead of writing the > emulated value to MSR? > > I think writing the emulated value to MSR is better. As I mentioned in case 3, > if hardware has cpuid faulting feature. Using hardware capability is more > efficient than emulation that the emulation solution needs VM exit to inject > #GP.
You can do that too, yes. You can add it to vmx_msr_index and it will be handled like that.
However, that wouldn't work on AMD (which doesn't use the kvm_define_shared_msr infrastructure) and also on hosts that don't have MSR_MISC_FEATURES_ENABLES, so my suggestion is to add this optimization as a separate patch.
Paolo
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