lkml.org 
[lkml]   [2021]   [Dec]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v2 23/23] kvm: x86: Disable RDMSR interception of IA32_XFD_ERR
From
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);
>

\
 
 \ /
  Last update: 2021-12-20 10:09    [W:0.459 / U:0.704 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site