KVM: VMX: Save HOST_CR3 in vmx_set_host_fs_gs()

The host CR3 in the vcpu thread can only be changed when scheduling,
so commit 15ad9762 ("KVM: VMX: Save HOST_CR3 in vmx_prepare_switch_to_guest()")
changed vmx.c to only save it in vmx_prepare_switch_to_guest().

However, it also has to be synced in vmx_sync_vmcs_host_state() when switching VMCS.
vmx_set_host_fs_gs() is called in both places, so rename it to
vmx_set_vmcs_host_state() and make it update HOST_CR3.

Fixes: 15ad9762 ("KVM: VMX: Save HOST_CR3 in vmx_prepare_switch_to_guest()")
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Message-Id: <20211216021938.11752-2-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -245,7 +245,8 @@ static void vmx_sync_vmcs_host_state(struct vcpu_vmx *vmx,
 	src = &prev->host_state;
 	dest = &vmx->loaded_vmcs->host_state;
 
-	vmx_set_host_fs_gs(dest, src->fs_sel, src->gs_sel, src->fs_base, src->gs_base);
+	vmx_set_vmcs_host_state(dest, src->cr3, src->fs_sel, src->gs_sel,
+				src->fs_base, src->gs_base);
 	dest->ldt_sel = src->ldt_sel;
 #ifdef CONFIG_X86_64
 	dest->ds_sel = src->ds_sel;

arch/x86/kvm/vmx/vmx.c

@@ -1069,9 +1069,14 @@ static void pt_guest_exit(struct vcpu_vmx *vmx)
 		wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
 }
 
-void vmx_set_host_fs_gs(struct vmcs_host_state *host, u16 fs_sel, u16 gs_sel,
-			unsigned long fs_base, unsigned long gs_base)
+void vmx_set_vmcs_host_state(struct vmcs_host_state *host, unsigned long cr3,
+			     u16 fs_sel, u16 gs_sel,
+			     unsigned long fs_base, unsigned long gs_base)
 {
+	if (unlikely(cr3 != host->cr3)) {
+		vmcs_writel(HOST_CR3, cr3);
+		host->cr3 = cr3;
+	}
 	if (unlikely(fs_sel != host->fs_sel)) {
 		if (!(fs_sel & 7))
 			vmcs_write16(HOST_FS_SELECTOR, fs_sel);
@@ -1103,7 +1108,6 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
 #ifdef CONFIG_X86_64
 	int cpu = raw_smp_processor_id();
 #endif
-	unsigned long cr3;
 	unsigned long fs_base, gs_base;
 	u16 fs_sel, gs_sel;
 	int i;
@@ -1167,14 +1171,8 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
 	gs_base = segment_base(gs_sel);
 #endif
 
-	vmx_set_host_fs_gs(host_state, fs_sel, gs_sel, fs_base, gs_base);
-
-	/* Host CR3 including its PCID is stable when guest state is loaded. */
-	cr3 = __get_current_cr3_fast();
-	if (unlikely(cr3 != host_state->cr3)) {
-		vmcs_writel(HOST_CR3, cr3);
-		host_state->cr3 = cr3;
-	}
+	vmx_set_vmcs_host_state(host_state, __get_current_cr3_fast(),
+				fs_sel, gs_sel, fs_base, gs_base);
 
 	vmx->guest_state_loaded = true;
 }

arch/x86/kvm/vmx/vmx.h

@@ -371,8 +371,9 @@ int allocate_vpid(void);
 void free_vpid(int vpid);
 void vmx_set_constant_host_state(struct vcpu_vmx *vmx);
 void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu);
-void vmx_set_host_fs_gs(struct vmcs_host_state *host, u16 fs_sel, u16 gs_sel,
-			unsigned long fs_base, unsigned long gs_base);
+void vmx_set_vmcs_host_state(struct vmcs_host_state *host, unsigned long cr3,
+			     u16 fs_sel, u16 gs_sel,
+			     unsigned long fs_base, unsigned long gs_base);
 int vmx_get_cpl(struct kvm_vcpu *vcpu);
 bool vmx_emulation_required(struct kvm_vcpu *vcpu);
 unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu);