On 3/8/2025 5:20 AM, Paolo Bonzini wrote:
From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
On entering/exiting TDX vcpu, preserved or clobbered CPU state is different
from the VMX case. Add TDX hooks to save/restore host/guest CPU state.
Save/restore kernel GS base MSR.
Reviewed-by: Xiayao Li <xiaoyao.li@xxxxxxxxx>
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Message-ID: <20250129095902.16391-7-adrian.hunter@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/vmx/main.c | 24 +++++++++++++++++++++--
arch/x86/kvm/vmx/tdx.c | 40 ++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/vmx/x86_ops.h | 4 ++++
3 files changed, 66 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
index 037590fc05e9..c0497ed0c9be 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -145,6 +145,26 @@ static void vt_update_cpu_dirty_logging(struct kvm_vcpu *vcpu)
vmx_update_cpu_dirty_logging(vcpu);
}
+static void vt_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
+{
+ if (is_td_vcpu(vcpu)) {
+ tdx_prepare_switch_to_guest(vcpu);
+ return;
+ }
+
+ vmx_prepare_switch_to_guest(vcpu);
+}
+
+static void vt_vcpu_put(struct kvm_vcpu *vcpu)
+{
+ if (is_td_vcpu(vcpu)) {
+ tdx_vcpu_put(vcpu);
+ return;
+ }
+
+ vmx_vcpu_put(vcpu);
+}
+
static int vt_vcpu_pre_run(struct kvm_vcpu *vcpu)
{
if (is_td_vcpu(vcpu))
@@ -265,9 +285,9 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
.vcpu_free = vt_vcpu_free,
.vcpu_reset = vt_vcpu_reset,
- .prepare_switch_to_guest = vmx_prepare_switch_to_guest,
+ .prepare_switch_to_guest = vt_prepare_switch_to_guest,
.vcpu_load = vt_vcpu_load,
- .vcpu_put = vmx_vcpu_put,
+ .vcpu_put = vt_vcpu_put,
.update_exception_bitmap = vmx_update_exception_bitmap,
.get_feature_msr = vmx_get_feature_msr,
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index f50565f45b6a..94e08fdcb775 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -3,6 +3,7 @@
#include <linux/cpu.h>
#include <asm/cpufeature.h>
#include <linux/misc_cgroup.h>
+#include <linux/mmu_context.h>
#include <asm/tdx.h>
#include "capabilities.h"
#include "mmu.h"
@@ -12,6 +13,7 @@
#include "vmx.h"
#include "mmu/spte.h"
#include "common.h"
+#include "posted_intr.h"
#include <trace/events/kvm.h>
#include "trace.h"
@@ -624,6 +626,44 @@ void tdx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
local_irq_enable();
}
+/*
+ * Compared to vmx_prepare_switch_to_guest(), there is not much to do
+ * as SEAMCALL/SEAMRET calls take care of most of save and restore.
+ */
+void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vt *vt = to_vt(vcpu);
+
+ if (vt->guest_state_loaded)
+ return;
+
+ if (likely(is_64bit_mm(current->mm)))
+ vt->msr_host_kernel_gs_base = current->thread.gsbase;
+ else
+ vt->msr_host_kernel_gs_base = read_msr(MSR_KERNEL_GS_BASE);
+
+ vt->guest_state_loaded = true;
+}
+
+static void tdx_prepare_switch_to_host(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vt *vt = to_vt(vcpu);
+
+ if (!vt->guest_state_loaded)
+ return;
+
+ ++vcpu->stat.host_state_reload;
+ wrmsrl(MSR_KERNEL_GS_BASE, vt->msr_host_kernel_gs_base);
+
+ vt->guest_state_loaded = false;
+}
+
+void tdx_vcpu_put(struct kvm_vcpu *vcpu)
+{
+ vmx_vcpu_pi_put(vcpu);
+ tdx_prepare_switch_to_host(vcpu);
+}
+
void tdx_vcpu_free(struct kvm_vcpu *vcpu)
{
struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
index 578c26d3aec4..cd18e9b1e124 100644
--- a/arch/x86/kvm/vmx/x86_ops.h
+++ b/arch/x86/kvm/vmx/x86_ops.h
@@ -133,6 +133,8 @@ void tdx_vcpu_free(struct kvm_vcpu *vcpu);
void tdx_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
int tdx_vcpu_pre_run(struct kvm_vcpu *vcpu);
fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit);
+void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu);
+void tdx_vcpu_put(struct kvm_vcpu *vcpu);
int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp);
@@ -164,6 +166,8 @@ static inline fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediat
{
return EXIT_FASTPATH_NONE;
}
+static inline void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) {}
+static inline void tdx_vcpu_put(struct kvm_vcpu *vcpu) {}
static inline int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { return -EOPNOTSUPP; }
