[PATCH 04/15] KVM: VMX: Save HOST_CR3 in vmx_prepare_switch_to_guest()

Lai Jiangshan
2021-11-18T11:09:37Z

The host CR3 in the vcpu thread can only be changed when scheduling.
Moving the code in vmx_prepare_switch_to_guest() makes the code
simpler.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
arch/x86/kvm/vmx/nested.c | 8 +-------
arch/x86/kvm/vmx/vmx.c | 17 ++++++++++-------
2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 2d9565b37fe0..d8d0dbc4fc18 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3028,7 +3028,7 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu,
static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
- unsigned long cr3, cr4;
+ unsigned long cr4;
bool vm_fail;

if (!nested_early_check)
@@ -3051,12 +3051,6 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
*/
vmcs_writel(GUEST_RFLAGS, 0);

- cr3 = __get_current_cr3_fast();
- if (unlikely(cr3 != vmx->loaded_vmcs->host_state.cr3)) {
- vmcs_writel(HOST_CR3, cr3);
- vmx->loaded_vmcs->host_state.cr3 = cr3;
- }
-
cr4 = cr4_read_shadow();
if (unlikely(cr4 != vmx->loaded_vmcs->host_state.cr4)) {
vmcs_writel(HOST_CR4, cr4);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index fc7aa7f30ad5..e8a41fdc3c4d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1103,6 +1103,7 @@ 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;
@@ -1167,6 +1168,14 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
#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->guest_state_loaded = true;
}

@@ -6590,7 +6599,7 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
- unsigned long cr3, cr4;
+ unsigned long cr4;

/* Record the guest's net vcpu time for enforced NMI injections. */
if (unlikely(!enable_vnmi &&
@@ -6634,12 +6643,6 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
if (kvm_register_is_dirty(vcpu, VCPU_REGS_RIP))
vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]);

- cr3 = __get_current_cr3_fast();
- if (unlikely(cr3 != vmx->loaded_vmcs->host_state.cr3)) {
- vmcs_writel(HOST_CR3, cr3);
- vmx->loaded_vmcs->host_state.cr3 = cr3;
- }
-
cr4 = cr4_read_shadow();
if (unlikely(cr4 != vmx->loaded_vmcs->host_state.cr4)) {
vmcs_writel(HOST_CR4, cr4);
--
2.19.1.6.gb485710b