KVM: vmx: compute need to reload FS/GS/LDT on demand

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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 5 insertions, 13 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index a135c91d44f8..c8a583ff7bf2 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -824,8 +824,6 @@ 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;
@@ -2681,7 +2679,6 @@ 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);
@@ -2711,20 +2708,15 @@ 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);
@@ -2749,7 +2741,7 @@ 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);
@@ -2757,7 +2749,7 @@ 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)) {