X86/KVM: Properly update 'tsc_offset' to represent the running guest

Update 'tsc_offset' on vmentry/vmexit of L2 guests to ensure that it always
captures the TSC_OFFSET of the running guest whether it is the L1 or L2
guest.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Jim Mattson <jmattson@google.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
[AMD changes, fix update_ia32_tsc_adjust_msr. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

4 files changed, 56 insertions, 22 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 949c977bc4c9..c25775fad4ed 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1013,6 +1013,7 @@ struct kvm_x86_ops {
 
         bool (*has_wbinvd_exit)(void);
 
+        u64 (*read_l1_tsc_offset)(struct kvm_vcpu *vcpu);
         void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
 
         void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index b3ebc8ad6891..e77a536d0b7c 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1424,12 +1424,23 @@ static void init_sys_seg(struct vmcb_seg *seg, uint32_t type)
         seg->base = 0;
 }
 
+static u64 svm_read_l1_tsc_offset(struct kvm_vcpu *vcpu)
+{
+        struct vcpu_svm *svm = to_svm(vcpu);
+
+        if (is_guest_mode(vcpu))
+                return svm->nested.hsave->control.tsc_offset;
+
+        return vcpu->arch.tsc_offset;
+}
+
 static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
 {
         struct vcpu_svm *svm = to_svm(vcpu);
         u64 g_tsc_offset = 0;
 
         if (is_guest_mode(vcpu)) {
+                /* Write L1's TSC offset.  */
                 g_tsc_offset = svm->vmcb->control.tsc_offset -
                                svm->nested.hsave->control.tsc_offset;
                 svm->nested.hsave->control.tsc_offset = offset;
@@ -3323,6 +3334,7 @@ static int nested_svm_vmexit(struct vcpu_svm *svm)
         /* Restore the original control entries */
         copy_vmcb_control_area(vmcb, hsave);
 
+        svm->vcpu.arch.tsc_offset = svm->vmcb->control.tsc_offset;
         kvm_clear_exception_queue(&svm->vcpu);
         kvm_clear_interrupt_queue(&svm->vcpu);
 
@@ -3483,10 +3495,12 @@ static void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
         /* We don't want to see VMMCALLs from a nested guest */
         clr_intercept(svm, INTERCEPT_VMMCALL);
 
+        svm->vcpu.arch.tsc_offset += nested_vmcb->control.tsc_offset;
+        svm->vmcb->control.tsc_offset = svm->vcpu.arch.tsc_offset;
+
         svm->vmcb->control.virt_ext = nested_vmcb->control.virt_ext;
         svm->vmcb->control.int_vector = nested_vmcb->control.int_vector;
         svm->vmcb->control.int_state = nested_vmcb->control.int_state;
-        svm->vmcb->control.tsc_offset += nested_vmcb->control.tsc_offset;
         svm->vmcb->control.event_inj = nested_vmcb->control.event_inj;
         svm->vmcb->control.event_inj_err = nested_vmcb->control.event_inj_err;
 
@@ -7102,6 +7116,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 
         .has_wbinvd_exit = svm_has_wbinvd_exit,
 
+        .read_l1_tsc_offset = svm_read_l1_tsc_offset,
         .write_tsc_offset = svm_write_tsc_offset,
 
         .set_tdp_cr3 = set_tdp_cr3,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index a13c603bdefb..7207e6cc07c1 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2874,6 +2874,17 @@ static void setup_msrs(struct vcpu_vmx *vmx)
                 vmx_update_msr_bitmap(&vmx->vcpu);
 }
 
+static u64 vmx_read_l1_tsc_offset(struct kvm_vcpu *vcpu)
+{
+        struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
+
+        if (is_guest_mode(vcpu) &&
+            (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING))
+                return vcpu->arch.tsc_offset - vmcs12->tsc_offset;
+
+        return vcpu->arch.tsc_offset;
+}
+
 /*
  * reads and returns guest's timestamp counter "register"
  * guest_tsc = (host_tsc * tsc multiplier) >> 48 + tsc_offset
@@ -11175,11 +11186,8 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
                 vmcs_write64(GUEST_IA32_PAT, vmx->vcpu.arch.pat);
         }
 
-        if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
-                vmcs_write64(TSC_OFFSET,
-                        vcpu->arch.tsc_offset + vmcs12->tsc_offset);
-        else
-                vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
+        vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
+
         if (kvm_has_tsc_control)
                 decache_tsc_multiplier(vmx);
 
@@ -11427,6 +11435,7 @@ static int enter_vmx_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
         struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
         u32 msr_entry_idx;
         u32 exit_qual;
+        int r;
 
         enter_guest_mode(vcpu);
 
@@ -11436,26 +11445,21 @@ static int enter_vmx_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
         vmx_switch_vmcs(vcpu, &vmx->nested.vmcs02);
         vmx_segment_cache_clear(vmx);
 
-        if (prepare_vmcs02(vcpu, vmcs12, from_vmentry, &exit_qual)) {
-                leave_guest_mode(vcpu);
-                vmx_switch_vmcs(vcpu, &vmx->vmcs01);
-                nested_vmx_entry_failure(vcpu, vmcs12,
-                                         EXIT_REASON_INVALID_STATE, exit_qual);
-                return 1;
-        }
+        if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
+                vcpu->arch.tsc_offset += vmcs12->tsc_offset;
+
+        r = EXIT_REASON_INVALID_STATE;
+        if (prepare_vmcs02(vcpu, vmcs12, from_vmentry, &exit_qual))
+                goto fail;
 
         nested_get_vmcs12_pages(vcpu, vmcs12);
 
+        r = EXIT_REASON_MSR_LOAD_FAIL;
         msr_entry_idx = nested_vmx_load_msr(vcpu,
                                             vmcs12->vm_entry_msr_load_addr,
                                             vmcs12->vm_entry_msr_load_count);
-        if (msr_entry_idx) {
-                leave_guest_mode(vcpu);
-                vmx_switch_vmcs(vcpu, &vmx->vmcs01);
-                nested_vmx_entry_failure(vcpu, vmcs12,
-                                EXIT_REASON_MSR_LOAD_FAIL, msr_entry_idx);
-                return 1;
-        }
+        if (msr_entry_idx)
+                goto fail;
 
         /*
          * Note no nested_vmx_succeed or nested_vmx_fail here. At this point
@@ -11464,6 +11468,14 @@ static int enter_vmx_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
          * the success flag) when L2 exits (see nested_vmx_vmexit()).
          */
         return 0;
+
+fail:
+        if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
+                vcpu->arch.tsc_offset -= vmcs12->tsc_offset;
+        leave_guest_mode(vcpu);
+        vmx_switch_vmcs(vcpu, &vmx->vmcs01);
+        nested_vmx_entry_failure(vcpu, vmcs12, r, exit_qual);
+        return 1;
 }
 
 /*
@@ -12035,6 +12047,9 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
 
         leave_guest_mode(vcpu);
 
+        if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
+                vcpu->arch.tsc_offset -= vmcs12->tsc_offset;
+
         if (likely(!vmx->fail)) {
                 if (exit_reason == -1)
                         sync_vmcs12(vcpu, vmcs12);
@@ -12725,6 +12740,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
 
         .has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,
 
+        .read_l1_tsc_offset = vmx_read_l1_tsc_offset,
         .write_tsc_offset = vmx_write_tsc_offset,
 
         .set_tdp_cr3 = vmx_set_cr3,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0334b250e102..3f3fba58c960 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1490,7 +1490,7 @@ static void kvm_track_tsc_matching(struct kvm_vcpu *vcpu)
 
 static void update_ia32_tsc_adjust_msr(struct kvm_vcpu *vcpu, s64 offset)
 {
-        u64 curr_offset = vcpu->arch.tsc_offset;
+        u64 curr_offset = kvm_x86_ops->read_l1_tsc_offset(vcpu);
         vcpu->arch.ia32_tsc_adjust_msr += offset - curr_offset;
 }
 
@@ -1532,7 +1532,9 @@ static u64 kvm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
 
 u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
 {
-        return vcpu->arch.tsc_offset + kvm_scale_tsc(vcpu, host_tsc);
+        u64 tsc_offset = kvm_x86_ops->read_l1_tsc_offset(vcpu);
+
+        return tsc_offset + kvm_scale_tsc(vcpu, host_tsc);
 }
 EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);