KVM: x86: Unify TSC logic

Move the TSC control logic from the vendor backends into x86.c
by adding adjust_tsc_offset to x86 ops.  Now all TSC decisions
can be done in one place.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 57b4394..5ab1c3f 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -255,7 +255,6 @@ struct kvm_mmu {
 };
 
 struct kvm_vcpu_arch {
-       u64 host_tsc;
        /*
         * rip and regs accesses must go through
         * kvm_{register,rip}_{read,write} functions.
@@ -336,9 +335,10 @@ struct kvm_vcpu_arch {
 
        gpa_t time;
        struct pvclock_vcpu_time_info hv_clock;
-       unsigned int hv_clock_tsc_khz;
+       unsigned int hw_tsc_khz;
        unsigned int time_offset;
        struct page *time_page;
+       u64 last_host_tsc;
 
        bool nmi_pending;
        bool nmi_injected;
@@ -520,6 +520,7 @@ struct kvm_x86_ops {
        u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
        int (*get_lpage_level)(void);
        bool (*rdtscp_supported)(void);
+       void (*adjust_tsc_offset)(struct kvm_vcpu *vcpu, s64 adjustment);
 
        void (*set_supported_cpuid)(u32 func, struct kvm_cpuid_entry2 *entry);
 

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ea41c55..ff28f65 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -715,6 +715,15 @@ static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
        svm->vmcb->control.tsc_offset = offset + g_tsc_offset;
 }
 
+static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment)
+{
+       struct vcpu_svm *svm = to_svm(vcpu);
+
+       svm->vmcb->control.tsc_offset += adjustment;
+       if (is_nested(svm))
+               svm->nested.hsave->control.tsc_offset += adjustment;
+}
+
 static void init_vmcb(struct vcpu_svm *svm)
 {
        struct vmcb_control_area *control = &svm->vmcb->control;
@@ -961,20 +970,6 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
        int i;
 
        if (unlikely(cpu != vcpu->cpu)) {
-               u64 delta;
-
-               if (check_tsc_unstable()) {
-                       /*
-                        * Make sure that the guest sees a monotonically
-                        * increasing TSC.
-                        */
-                       delta = vcpu->arch.host_tsc - native_read_tsc();
-                       svm->vmcb->control.tsc_offset += delta;
-                       if (is_nested(svm))
-                               svm->nested.hsave->control.tsc_offset += delta;
-               }
-               vcpu->cpu = cpu;
-               kvm_migrate_timers(vcpu);
                svm->asid_generation = 0;
        }
 
@@ -990,8 +985,6 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
        ++vcpu->stat.host_state_reload;
        for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
                wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
-
-       vcpu->arch.host_tsc = native_read_tsc();
 }
 
 static unsigned long svm_get_rflags(struct kvm_vcpu *vcpu)
@@ -3553,6 +3546,7 @@ static struct kvm_x86_ops svm_x86_ops = {
        .has_wbinvd_exit = svm_has_wbinvd_exit,
 
        .write_tsc_offset = svm_write_tsc_offset,
+       .adjust_tsc_offset = svm_adjust_tsc_offset,
 };
 
 static int __init svm_init(void)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 138746d..275a81d 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -505,7 +505,6 @@ static void __vcpu_clear(void *arg)
                vmcs_clear(vmx->vmcs);
        if (per_cpu(current_vmcs, cpu) == vmx->vmcs)
                per_cpu(current_vmcs, cpu) = NULL;
-       rdtscll(vmx->vcpu.arch.host_tsc);
        list_del(&vmx->local_vcpus_link);
        vmx->vcpu.cpu = -1;
        vmx->launched = 0;
@@ -881,7 +880,6 @@ static void vmx_load_host_state(struct vcpu_vmx *vmx)
 static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
        struct vcpu_vmx *vmx = to_vmx(vcpu);
-       u64 tsc_this, delta, new_offset;
        u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
 
        if (!vmm_exclusive)
@@ -898,14 +896,12 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
                struct desc_ptr *gdt = &__get_cpu_var(host_gdt);
                unsigned long sysenter_esp;
 
-               kvm_migrate_timers(vcpu);
                kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
                local_irq_disable();
                list_add(&vmx->local_vcpus_link,
                         &per_cpu(vcpus_on_cpu, cpu));
                local_irq_enable();
 
-               vcpu->cpu = cpu;
                /*
                 * Linux uses per-cpu TSS and GDT, so set these when switching
                 * processors.
@@ -915,16 +911,6 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 
                rdmsrl(MSR_IA32_SYSENTER_ESP, sysenter_esp);
                vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */
-
-               /*
-                * Make sure the time stamp counter is monotonous.
-                */
-               rdtscll(tsc_this);
-               if (tsc_this < vcpu->arch.host_tsc) {
-                       delta = vcpu->arch.host_tsc - tsc_this;
-                       new_offset = vmcs_read64(TSC_OFFSET) + delta;
-                       vmcs_write64(TSC_OFFSET, new_offset);
-               }
        }
 }
 
@@ -1153,6 +1139,12 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
        vmcs_write64(TSC_OFFSET, offset);
 }
 
+static void vmx_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment)
+{
+       u64 offset = vmcs_read64(TSC_OFFSET);
+       vmcs_write64(TSC_OFFSET, offset + adjustment);
+}
+
 /*
  * Reads an msr value (of 'msr_index') into 'pdata'.
  * Returns 0 on success, non-0 otherwise.
@@ -4108,6 +4100,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 
        cpu = get_cpu();
        vmx_vcpu_load(&vmx->vcpu, cpu);
+       vmx->vcpu.cpu = cpu;
        err = vmx_vcpu_setup(vmx);
        vmx_vcpu_put(&vmx->vcpu);
        put_cpu();
@@ -4347,6 +4340,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
        .has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,
 
        .write_tsc_offset = vmx_write_tsc_offset,
+       .adjust_tsc_offset = vmx_adjust_tsc_offset,
 };
 
 static int __init vmx_init(void)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a8dee58..468fafa 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -973,9 +973,9 @@ static int kvm_write_guest_time(struct kvm_vcpu *v)
                return 1;
        }
 
-       if (unlikely(vcpu->hv_clock_tsc_khz != this_tsc_khz)) {
+       if (unlikely(vcpu->hw_tsc_khz != this_tsc_khz)) {
                kvm_set_time_scale(this_tsc_khz, &vcpu->hv_clock);
-               vcpu->hv_clock_tsc_khz = this_tsc_khz;
+               vcpu->hw_tsc_khz = this_tsc_khz;
        }
 
        /* With all the info we got, fill in the values */
@@ -1866,13 +1866,24 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
        }
 
        kvm_x86_ops->vcpu_load(vcpu, cpu);
-       kvm_request_guest_time_update(vcpu);
+       if (unlikely(vcpu->cpu != cpu)) {
+               /* Make sure TSC doesn't go backwards */
+               s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :
+                               native_read_tsc() - vcpu->arch.last_host_tsc;
+               if (tsc_delta < 0)
+                       mark_tsc_unstable("KVM discovered backwards TSC");
+               if (check_tsc_unstable())
+                       kvm_x86_ops->adjust_tsc_offset(vcpu, -tsc_delta);
+               kvm_migrate_timers(vcpu);
+               vcpu->cpu = cpu;
+       }
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
        kvm_x86_ops->vcpu_put(vcpu);
        kvm_put_guest_fpu(vcpu);
+       vcpu->arch.last_host_tsc = native_read_tsc();
 }
 
 static int is_efer_nx(void)