| Message ID | 20180723193250.13555-10-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: vmx: optimize VMWRITEs to host FS/GS fields | expand |
On Mon, Jul 23, 2018 at 12:33 PM Sean Christopherson <sean.j.christopherson@intel.com> wrote: > > The HOST_{FS,GS}_BASE fields are guaranteed to be written prior to > VMENTER, by way of vmx_prepare_switch_to_guest(). Initialize the > fields to zero for 64-bit kernels instead of pulling the base values > from their respective MSRs. In addition to eliminating two RDMSRs, > vmx_prepare_switch_to_guest() can safely assume the initial value of > the fields is zero in all cases. > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Reviewed-by: Peter Shier <pshier@google.com> Tested-by: Peter Shier <pshier@google.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index c66fcb01f355..b24cd74c905c 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -6223,9 +6223,6 @@ static void ept_set_mmio_spte_mask(void) */ static void vmx_vcpu_setup(struct vcpu_vmx *vmx) { -#ifdef CONFIG_X86_64 - unsigned long a; -#endif int i; if (enable_shadow_vmcs) { @@ -6280,15 +6277,8 @@ static void vmx_vcpu_setup(struct vcpu_vmx *vmx) vmcs_write16(HOST_FS_SELECTOR, 0); /* 22.2.4 */ vmcs_write16(HOST_GS_SELECTOR, 0); /* 22.2.4 */ vmx_set_constant_host_state(vmx); -#ifdef CONFIG_X86_64 - rdmsrl(MSR_FS_BASE, a); - vmcs_writel(HOST_FS_BASE, a); /* 22.2.4 */ - rdmsrl(MSR_GS_BASE, a); - vmcs_writel(HOST_GS_BASE, a); /* 22.2.4 */ -#else vmcs_writel(HOST_FS_BASE, 0); /* 22.2.4 */ vmcs_writel(HOST_GS_BASE, 0); /* 22.2.4 */ -#endif if (cpu_has_vmx_vmfunc()) vmcs_write64(VM_FUNCTION_CONTROL, 0);
The HOST_{FS,GS}_BASE fields are guaranteed to be written prior to VMENTER, by way of vmx_prepare_switch_to_guest(). Initialize the fields to zero for 64-bit kernels instead of pulling the base values from their respective MSRs. In addition to eliminating two RDMSRs, vmx_prepare_switch_to_guest() can safely assume the initial value of the fields is zero in all cases. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/vmx.c | 10 ---------- 1 file changed, 10 deletions(-)