[07/11] KVM: vmx: compute need to reload FS/GS/LDT on demand
diff mbox series

Message ID 20180723193250.13555-8-sean.j.christopherson@intel.com
State New
Headers show
Series
  • KVM: vmx: optimize VMWRITEs to host FS/GS fields
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Commit Message

Sean Christopherson July 23, 2018, 7:32 p.m. UTC
Remove fs_reload_needed and gs_ldt_reload_needed from host_state
and instead compute whether we need to reload various state at
the time we actually do the reload.  The state that is tracked
by the *_reload_needed variables is not any more volatile than
the trackers themselves.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kvm/vmx.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

Comments

Peter Shier July 24, 2018, 10:40 p.m. UTC | #1
On Mon, Jul 23, 2018 at 12:33 PM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> Remove fs_reload_needed and gs_ldt_reload_needed from host_state
> and instead compute whether we need to reload various state at
> the time we actually do the reload.  The state that is tracked
> by the *_reload_needed variables is not any more volatile than
> the trackers themselves.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>

Reviewed-by: Peter Shier <pshier@google.com>
Tested-by: Peter Shier <pshier@google.com>

Patch
diff mbox series

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 5e884ad3ec51..2f070f192906 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -804,8 +804,6 @@  struct vcpu_vmx {
 #ifdef CONFIG_X86_64
 		u16           ds_sel, es_sel;
 #endif
-		int           gs_ldt_reload_needed;
-		int           fs_reload_needed;
 	} host_state;
 	struct {
 		int vm86_active;
@@ -2590,7 +2588,6 @@  static void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
 	 * allow segment selectors with cpl > 0 or ti == 1.
 	 */
 	vmx->host_state.ldt_sel = kvm_read_ldt();
-	vmx->host_state.gs_ldt_reload_needed = vmx->host_state.ldt_sel;
 
 #ifdef CONFIG_X86_64
 	savesegment(ds, vmx->host_state.ds_sel);
@@ -2613,20 +2610,15 @@  static void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
 #endif
 
 	vmx->host_state.fs_sel = fs_sel;
-	if (!(fs_sel & 7)) {
+	if (!(fs_sel & 7))
 		vmcs_write16(HOST_FS_SELECTOR, fs_sel);
-		vmx->host_state.fs_reload_needed = 0;
-	} else {
+	else
 		vmcs_write16(HOST_FS_SELECTOR, 0);
-		vmx->host_state.fs_reload_needed = 1;
-	}
 	vmx->host_state.gs_sel = gs_sel;
 	if (!(gs_sel & 7))
 		vmcs_write16(HOST_GS_SELECTOR, gs_sel);
-	else {
+	else
 		vmcs_write16(HOST_GS_SELECTOR, 0);
-		vmx->host_state.gs_ldt_reload_needed = 1;
-	}
 
 	vmcs_writel(HOST_FS_BASE, fs_base);
 	vmcs_writel(HOST_GS_BASE, gs_base);
@@ -2653,7 +2645,7 @@  static void vmx_prepare_switch_to_host(struct vcpu_vmx *vmx)
 	if (is_long_mode(&vmx->vcpu))
 		rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
 #endif
-	if (vmx->host_state.gs_ldt_reload_needed) {
+	if (vmx->host_state.ldt_sel || (vmx->host_state.gs_sel & 7)) {
 		kvm_load_ldt(vmx->host_state.ldt_sel);
 #ifdef CONFIG_X86_64
 		load_gs_index(vmx->host_state.gs_sel);
@@ -2661,7 +2653,7 @@  static void vmx_prepare_switch_to_host(struct vcpu_vmx *vmx)
 		loadsegment(gs, vmx->host_state.gs_sel);
 #endif
 	}
-	if (vmx->host_state.fs_reload_needed)
+	if (vmx->host_state.fs_sel & 7)
 		loadsegment(fs, vmx->host_state.fs_sel);
 #ifdef CONFIG_X86_64
 	if (unlikely(vmx->host_state.ds_sel | vmx->host_state.es_sel)) {