From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
On entering/exiting TDX vcpu, Preserved or clobbered CPU state is different
from VMX case. Add TDX hooks to save/restore host/guest CPU state.
Save/restore kernel GS base MSR.
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/vmx/main.c | 30 ++++++++++++++++++++++++++--
arch/x86/kvm/vmx/tdx.c | 41 ++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/vmx/tdx.h | 4 ++++
arch/x86/kvm/vmx/x86_ops.h | 4 ++++
4 files changed, 77 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
index be5eb3a6965d..d4edb479648e 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -169,6 +169,32 @@ static void vt_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
vmx_vcpu_reset(vcpu, init_event);
}
+static void vt_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
+{
+ /*
+ * All host state is saved/restored across SEAMCALL/SEAMRET, and the
+ * guest state of a TD is obviously off limits. Deferring MSRs and DRs
+ * is pointless because the TDX module needs to load *something* so as
+ * not to expose guest state.
+ */
+ 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))
@@ -304,9 +330,9 @@ 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 = vmx_vcpu_load,
- .vcpu_put = vmx_vcpu_put,
+ .vcpu_put = vt_vcpu_put,
.update_exception_bitmap = vmx_update_exception_bitmap,
.get_msr_feature = vmx_get_msr_feature,
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index a2c7569ddeb4..0a71601c78f9 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/cpu.h>
+#include <linux/mmu_context.h>
#include <asm/tdx.h>
@@ -372,6 +373,8 @@ u8 tdx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
int tdx_vcpu_create(struct kvm_vcpu *vcpu)
{
+ struct vcpu_tdx *tdx = to_tdx(vcpu);
+
/*
* On cpu creation, cpuid entry is blank. Forcibly enable
* X2APIC feature to allow X2APIC.
@@ -396,9 +399,45 @@ int tdx_vcpu_create(struct kvm_vcpu *vcpu)
vcpu->arch.guest_state_protected =
!(to_kvm_tdx(vcpu->kvm)->attributes & TDX_TD_ATTRIBUTE_DEBUG);
+ tdx->host_state_need_save = true;
+ tdx->host_state_need_restore = false;
+
return 0;
}
+void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_tdx *tdx = to_tdx(vcpu);
+
+ if (!tdx->host_state_need_save)
+ return;
+
+ if (likely(is_64bit_mm(current->mm)))
+ tdx->msr_host_kernel_gs_base = current->thread.gsbase;
+ else
+ tdx->msr_host_kernel_gs_base = read_msr(MSR_KERNEL_GS_BASE);
+
+ tdx->host_state_need_save = false;
+}
+
+static void tdx_prepare_switch_to_host(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_tdx *tdx = to_tdx(vcpu);
+
+ tdx->host_state_need_save = true;
+ if (!tdx->host_state_need_restore)
+ return;
+
+ wrmsrl(MSR_KERNEL_GS_BASE, tdx->msr_host_kernel_gs_base);
+ tdx->host_state_need_restore = 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 vcpu_tdx *tdx = to_tdx(vcpu);
@@ -469,6 +508,8 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu)
tdx_vcpu_enter_exit(vcpu, tdx);
+ tdx->host_state_need_restore = true;
+
vcpu->arch.regs_avail &= ~VMX_REGS_LAZY_LOAD_SET;
trace_kvm_exit(vcpu, KVM_ISA_VMX);
diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
index f54f27ef006c..a3c64a2ec9e0 100644
--- a/arch/x86/kvm/vmx/tdx.h
+++ b/arch/x86/kvm/vmx/tdx.h
@@ -66,6 +66,10 @@ struct vcpu_tdx {
bool initialized;
+ bool host_state_need_save;
+ bool host_state_need_restore;
+ u64 msr_host_kernel_gs_base;
+
/*
* Dummy to make pmu_intel not corrupt memory.
* TODO: Support PMU for TDX. Future work.
diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
index fa41d6352d52..8fcc5807e594 100644
--- a/arch/x86/kvm/vmx/x86_ops.h
+++ b/arch/x86/kvm/vmx/x86_ops.h
@@ -152,6 +152,8 @@ int tdx_vcpu_create(struct kvm_vcpu *vcpu);
void tdx_vcpu_free(struct kvm_vcpu *vcpu);
void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event);
fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu);
+void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu);
+void tdx_vcpu_put(struct kvm_vcpu *vcpu);
u8 tdx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp);
@@ -180,6 +182,8 @@ static inline int tdx_vcpu_create(struct kvm_vcpu *vcpu) { return -EOPNOTSUPP; }
static inline void tdx_vcpu_free(struct kvm_vcpu *vcpu) {}
static inline void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) {}
static inline fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu) { 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 u8 tdx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio) { return 0; }
static inline int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { return -EOPNOTSUPP; }
--
2.25.1
