KVM: x86: drop TSC offsetting kvm_x86_ops to fix KVM_GET/SET_CLOCK

Since commit 243d7e3daabf ("kvm: x86: add tsc_offset field to struct
kvm_vcpu_arch", 2016-09-07) the offset between host and L1 TSC is
cached and need not be fished out of the VMCS or VMCB.  This means
that we can implement adjust_tsc_offset_guest and read_l1_tsc
entirely in generic code.  The simplification is particularly
significant for VMX code, where vmx->nested.vmcs01_tsc_offset
was duplicating what is now in vcpu->arch.tsc_offset.  Therefore
the vmcs01_tsc_offset can be dropped completely.

More importantly, this fixes KVM_GET_CLOCK/KVM_SET_CLOCK
which, after commit 4e7f0f01b367 ("KVM: x86: introduce get_kvmclock_ns",
2016-09-01) called read_l1_tsc while the VMCS was not loaded.
It thus returned bogus values on Intel CPUs.

Fixes: 4e7f0f01b367d95b9149a8ca54151b961d7fd76e
Reported-by: Roman Kagan <rkagan@virtuozzo.com>
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4b20f7304b9c241f58dcaa6b33a486a7308af9c4..bdde80731f490ecc05af1234d99c6ae2820975d4 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -948,7 +948,6 @@ struct kvm_x86_ops {
        int (*get_lpage_level)(void);
        bool (*rdtscp_supported)(void);
        bool (*invpcid_supported)(void);
-       void (*adjust_tsc_offset_guest)(struct kvm_vcpu *vcpu, s64 adjustment);
 
        void (*set_tdp_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);
 
@@ -958,8 +957,6 @@ struct kvm_x86_ops {
 
        void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
 
-       u64 (*read_l1_tsc)(struct kvm_vcpu *vcpu, u64 host_tsc);
-
        void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);
 
        int (*check_intercept)(struct kvm_vcpu *vcpu,

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index f8157a36ab099a2d3336ef422208b5f078154064..8ca1eca5038d5ce50f6376393abb83df79c4524f 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1138,21 +1138,6 @@ static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
        mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
 }
 
-static void svm_adjust_tsc_offset_guest(struct kvm_vcpu *vcpu, s64 adjustment)
-{
-       struct vcpu_svm *svm = to_svm(vcpu);
-
-       svm->vmcb->control.tsc_offset += adjustment;
-       if (is_guest_mode(vcpu))
-               svm->nested.hsave->control.tsc_offset += adjustment;
-       else
-               trace_kvm_write_tsc_offset(vcpu->vcpu_id,
-                                    svm->vmcb->control.tsc_offset - adjustment,
-                                    svm->vmcb->control.tsc_offset);
-
-       mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
-}
-
 static void avic_init_vmcb(struct vcpu_svm *svm)
 {
        struct vmcb *vmcb = svm->vmcb;
@@ -3449,12 +3434,6 @@ static int cr8_write_interception(struct vcpu_svm *svm)
        return 0;
 }
 
-static u64 svm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
-{
-       struct vmcb *vmcb = get_host_vmcb(to_svm(vcpu));
-       return vmcb->control.tsc_offset + host_tsc;
-}
-
 static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
@@ -5422,8 +5401,6 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
        .has_wbinvd_exit = svm_has_wbinvd_exit,
 
        .write_tsc_offset = svm_write_tsc_offset,
-       .adjust_tsc_offset_guest = svm_adjust_tsc_offset_guest,
-       .read_l1_tsc = svm_read_l1_tsc,
 
        .set_tdp_cr3 = set_tdp_cr3,
 

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 74a4df993a515837d407082588ae16db9389474b..754c3a7f444a79d223647f655d283bd4b90fc270 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -421,7 +421,6 @@ struct nested_vmx {
        /* vmcs02_list cache of VMCSs recently used to run L2 guests */
        struct list_head vmcs02_pool;
        int vmcs02_num;
-       u64 vmcs01_tsc_offset;
        bool change_vmcs01_virtual_x2apic_mode;
        /* L2 must run next, and mustn't decide to exit to L1. */
        bool nested_run_pending;
@@ -2604,20 +2603,6 @@ static u64 guest_read_tsc(struct kvm_vcpu *vcpu)
        return kvm_scale_tsc(vcpu, host_tsc) + tsc_offset;
 }
 
-/*
- * Like guest_read_tsc, but always returns L1's notion of the timestamp
- * counter, even if a nested guest (L2) is currently running.
- */
-static u64 vmx_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
-{
-       u64 tsc_offset;
-
-       tsc_offset = is_guest_mode(vcpu) ?
-               to_vmx(vcpu)->nested.vmcs01_tsc_offset :
-               vmcs_read64(TSC_OFFSET);
-       return host_tsc + tsc_offset;
-}
-
 /*
  * writes 'offset' into guest's timestamp counter offset register
  */
@@ -2631,7 +2616,6 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
                 * to the newly set TSC to get L2's TSC.
                 */
                struct vmcs12 *vmcs12;
-               to_vmx(vcpu)->nested.vmcs01_tsc_offset = offset;
                /* recalculate vmcs02.TSC_OFFSET: */
                vmcs12 = get_vmcs12(vcpu);
                vmcs_write64(TSC_OFFSET, offset +
@@ -2644,19 +2628,6 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
        }
 }
 
-static void vmx_adjust_tsc_offset_guest(struct kvm_vcpu *vcpu, s64 adjustment)
-{
-       u64 offset = vmcs_read64(TSC_OFFSET);
-
-       vmcs_write64(TSC_OFFSET, offset + adjustment);
-       if (is_guest_mode(vcpu)) {
-               /* Even when running L2, the adjustment needs to apply to L1 */
-               to_vmx(vcpu)->nested.vmcs01_tsc_offset += adjustment;
-       } else
-               trace_kvm_write_tsc_offset(vcpu->vcpu_id, offset,
-                                          offset + adjustment);
-}
-
 static bool guest_cpuid_has_vmx(struct kvm_vcpu *vcpu)
 {
        struct kvm_cpuid_entry2 *best = kvm_find_cpuid_entry(vcpu, 1, 0);
@@ -10061,9 +10032,9 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 
        if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
                vmcs_write64(TSC_OFFSET,
-                       vmx->nested.vmcs01_tsc_offset + vmcs12->tsc_offset);
+                       vcpu->arch.tsc_offset + vmcs12->tsc_offset);
        else
-               vmcs_write64(TSC_OFFSET, vmx->nested.vmcs01_tsc_offset);
+               vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
        if (kvm_has_tsc_control)
                decache_tsc_multiplier(vmx);
 
@@ -10293,8 +10264,6 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 
        enter_guest_mode(vcpu);
 
-       vmx->nested.vmcs01_tsc_offset = vmcs_read64(TSC_OFFSET);
-
        if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
                vmx->nested.vmcs01_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
 
@@ -10818,7 +10787,7 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
        load_vmcs12_host_state(vcpu, vmcs12);
 
        /* Update any VMCS fields that might have changed while L2 ran */
-       vmcs_write64(TSC_OFFSET, vmx->nested.vmcs01_tsc_offset);
+       vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
        if (vmx->hv_deadline_tsc == -1)
                vmcs_clear_bits(PIN_BASED_VM_EXEC_CONTROL,
                                PIN_BASED_VMX_PREEMPTION_TIMER);
@@ -11339,8 +11308,6 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
        .has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,
 
        .write_tsc_offset = vmx_write_tsc_offset,
-       .adjust_tsc_offset_guest = vmx_adjust_tsc_offset_guest,
-       .read_l1_tsc = vmx_read_l1_tsc,
 
        .set_tdp_cr3 = vmx_set_cr3,
 

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e954be8a3185dd619db457dac75266ecb85a5b34..3017de0431bd743551e37ea7296acdb60ce1773e 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1409,7 +1409,7 @@ 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 kvm_x86_ops->read_l1_tsc(vcpu, kvm_scale_tsc(vcpu, host_tsc));
+       return vcpu->arch.tsc_offset + kvm_scale_tsc(vcpu, host_tsc);
 }
 EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);
 
@@ -1547,7 +1547,7 @@ EXPORT_SYMBOL_GPL(kvm_write_tsc);
 static inline void adjust_tsc_offset_guest(struct kvm_vcpu *vcpu,
                                           s64 adjustment)
 {
-       kvm_x86_ops->adjust_tsc_offset_guest(vcpu, adjustment);
+       kvm_vcpu_write_tsc_offset(vcpu, vcpu->arch.tsc_offset + adjustment);
 }
 
 static inline void adjust_tsc_offset_host(struct kvm_vcpu *vcpu, s64 adjustment)
@@ -1555,7 +1555,7 @@ static inline void adjust_tsc_offset_host(struct kvm_vcpu *vcpu, s64 adjustment)
        if (vcpu->arch.tsc_scaling_ratio != kvm_default_tsc_scaling_ratio)
                WARN_ON(adjustment < 0);
        adjustment = kvm_scale_tsc(vcpu, (u64) adjustment);
-       kvm_x86_ops->adjust_tsc_offset_guest(vcpu, adjustment);
+       adjust_tsc_offset_guest(vcpu, adjustment);
 }
 
 #ifdef CONFIG_X86_64