Messages in this thread | | | Date | Mon, 20 Dec 2021 10:08:49 +0100 | Subject | Re: [PATCH v2 23/23] kvm: x86: Disable RDMSR interception of IA32_XFD_ERR | From | Paolo Bonzini <> |
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On 12/17/21 16:30, Jing Liu wrote: > Also disable read emulation of IA32_XFD_ERR MSR at the same point > where r/w emulation of IA32_XFD MSR is disabled. This saves one > unnecessary VM-exit in guest #NM handler, given that the MSR is > already restored with the guest value before the guest is resumed. > > Signed-off-by: Jing Liu <jing2.liu@intel.com>
Why not do this unconditionally (i.e. in patch 13, with the call to vmx_disable_intercept_for_msr in function vmx_create_vcpu)?
Thanks,
Paolo
> --- > arch/x86/kvm/vmx/vmx.c | 2 ++ > arch/x86/kvm/vmx/vmx.h | 2 +- > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 97a823a3f23f..b66a005f076b 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -163,6 +163,7 @@ static u32 vmx_possible_passthrough_msrs[MAX_POSSIBLE_PASSTHROUGH_MSRS] = { > MSR_GS_BASE, > MSR_KERNEL_GS_BASE, > MSR_IA32_XFD, > + MSR_IA32_XFD_ERR, > #endif > MSR_IA32_SYSENTER_CS, > MSR_IA32_SYSENTER_ESP, > @@ -1934,6 +1935,7 @@ static u64 vcpu_supported_debugctl(struct kvm_vcpu *vcpu) > static void vmx_set_xfd_passthrough(struct kvm_vcpu *vcpu) > { > vmx_disable_intercept_for_msr(vcpu, MSR_IA32_XFD, MSR_TYPE_RW); > + vmx_disable_intercept_for_msr(vcpu, MSR_IA32_XFD_ERR, MSR_TYPE_R); > vcpu->arch.xfd_out_of_sync = true; > } > #endif > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h > index bf9d3051cd6c..0a00242a91e7 100644 > --- a/arch/x86/kvm/vmx/vmx.h > +++ b/arch/x86/kvm/vmx/vmx.h > @@ -340,7 +340,7 @@ struct vcpu_vmx { > struct lbr_desc lbr_desc; > > /* Save desired MSR intercept (read: pass-through) state */ > -#define MAX_POSSIBLE_PASSTHROUGH_MSRS 14 > +#define MAX_POSSIBLE_PASSTHROUGH_MSRS 15 > struct { > DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS); > DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS); >
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