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@xxxxxxxxx>
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);
