Revert "KVM: VMX: Save HOST_CR3 in vmx_set_host_fs_gs()"

Undo a nested VMX fix as a step toward reverting the commit it fixed,
15ad9762d69f ("KVM: VMX: Save HOST_CR3 in vmx_prepare_switch_to_guest()"),
as the underlying premise that "host CR3 in the vcpu thread can only be
changed when scheduling" is wrong.

This reverts commit a9f2705ec84449e3b8d70c804766f8e97e23080d.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220224191917.3508476-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index ba34e94..c12f950 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -246,8 +246,7 @@ static void vmx_sync_vmcs_host_state(struct vcpu_vmx *vmx,
        src = &prev->host_state;
        dest = &vmx->loaded_vmcs->host_state;
 
-       vmx_set_vmcs_host_state(dest, src->cr3, src->fs_sel, src->gs_sel,
-                               src->fs_base, src->gs_base);
+       vmx_set_host_fs_gs(dest, 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;

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index efda5e4..beb68cd 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1080,14 +1080,9 @@ static void pt_guest_exit(struct vcpu_vmx *vmx)
                wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
 }
 
-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)
+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)
 {
-       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);
@@ -1119,6 +1114,7 @@ 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;
@@ -1182,8 +1178,14 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
        gs_base = segment_base(gs_sel);
 #endif
 
-       vmx_set_vmcs_host_state(host_state, __get_current_cr3_fast(),
-                               fs_sel, gs_sel, fs_base, gs_base);
+       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->guest_state_loaded = true;
 }

diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 7f2c82e..9c6bfcd 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -374,9 +374,8 @@ 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_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);
+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);
 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);