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KVM: vmx: always initialize HOST_{FS,GS}_BASE to zero during setup

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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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2018-07-23 12:32:48 -07:00 committed by Paolo Bonzini
parent d7ee039e2b
commit f3bbc0dced
1 changed files with 0 additions and 10 deletions
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10
arch/x86/kvm/vmx.c
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@ -6361,9 +6361,6 @@ static void ept_set_mmio_spte_mask(void)
*/ */
static void vmx_vcpu_setup(struct vcpu_vmx *vmx) static void vmx_vcpu_setup(struct vcpu_vmx *vmx)
{ {
#ifdef CONFIG_X86_64
unsigned long a;
#endif
int i; int i;
if (enable_shadow_vmcs) { if (enable_shadow_vmcs) {
@ -6418,15 +6415,8 @@ static void vmx_vcpu_setup(struct vcpu_vmx *vmx)
vmcs_write16(HOST_FS_SELECTOR, 0); /* 22.2.4 */ vmcs_write16(HOST_FS_SELECTOR, 0); /* 22.2.4 */
vmcs_write16(HOST_GS_SELECTOR, 0); /* 22.2.4 */ vmcs_write16(HOST_GS_SELECTOR, 0); /* 22.2.4 */
vmx_set_constant_host_state(vmx); 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_FS_BASE, 0); /* 22.2.4 */
vmcs_writel(HOST_GS_BASE, 0); /* 22.2.4 */ vmcs_writel(HOST_GS_BASE, 0); /* 22.2.4 */
#endif
if (cpu_has_vmx_vmfunc()) if (cpu_has_vmx_vmfunc())
vmcs_write64(VM_FUNCTION_CONTROL, 0); vmcs_write64(VM_FUNCTION_CONTROL, 0);