Messages in this thread | | | Date | Thu, 12 May 2022 15:18:40 +0200 | Subject | Re: [PATCH v11 14/16] KVM: x86/vmx: Flip Arch LBREn bit on guest state change | From | Paolo Bonzini <> |
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On 5/11/22 09:43, Yang, Weijiang wrote: >> >> Instead of using flip_arch_lbr_ctl, SMM should save the value of the MSR >> in kvm_x86_ops->enter_smm, and restore it in kvm_x86_ops->leave_smm >> (feel free to do it only if guest_cpuid_has(vcpu, X86_FEATURE_LM), i.e. >> the 32-bit case can be ignored). > > In the case of migration in SMM, I assume kvm_x86_ops->enter_smm() > called in source side > > and kvm_x86_ops->leave_smm() is called at destination, then should the > saved LBREn be transferred > > to destination too? The destination can rely on the bit to defer setting > LBREn bit in
Hi, it's transferred automatically if the MSR is saved in the SMM save state area. Both enter_smm and leave_smm can access the save state area.
The enter_smm callback is called after saving "normal" state, and it has to save the state + clear the bit; likewise, the leave_smm callback is called before saving "normal" state and will restore the old value of the MSR.
Thanks,
Paolo
> VMCS until kvm_x86_ops->leave_smm() is called. is it good? thanks!
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