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KVM: VMX: Restore host's MSR_IA32_RTIT_CTL when it's not zero

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A minor optimization to WRMSR MSR_IA32_RTIT_CTL when necessary.

Opportunistically refine the comment to call out that KVM requires
VM_EXIT_CLEAR_IA32_RTIT_CTL to expose PT to the guest.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-Id: <20210827070249.924633-2-xiaoyao.li@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Xiaoyao Li 2021-08-27 15:02:43 +08:00 committed by Paolo Bonzini
parent 2839180ce5
commit 2e6e0d683b
1 changed files with 6 additions and 2 deletions
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8
arch/x86/kvm/vmx/vmx.c
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@ -1074,8 +1074,12 @@ static void pt_guest_exit(struct vcpu_vmx *vmx)
pt_load_msr(&vmx->pt_desc.host, vmx->pt_desc.addr_range);
}
/* Reload host state (IA32_RTIT_CTL will be cleared on VM exit). */
wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
/*
* KVM requires VM_EXIT_CLEAR_IA32_RTIT_CTL to expose PT to the guest,
* i.e. RTIT_CTL is always cleared on VM-Exit. Restore it if necessary.
*/
if (vmx->pt_desc.host.ctl)
wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
}
void vmx_set_host_fs_gs(struct vmcs_host_state *host, u16 fs_sel, u16 gs_sel,