[PATCH 06/18] Unify TSC logic

Zachary Amsden
2010-07-13T02:25:26Z

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.

Also, rename some variable in the VCPU structure to more accurately
reflect their actual content.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 5 +++--
arch/x86/kvm/svm.c | 26 ++++++++++----------------
arch/x86/kvm/vmx.c | 22 ++++++++--------------
arch/x86/kvm/x86.c | 18 +++++++++++++++---
4 files changed, 36 insertions(+), 35 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4b42893..324e892 100644
--- 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 7e7889d..b52222c 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -948,20 +948,6 @@ 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;
}

@@ -977,8 +963,6 @@ 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)
@@ -3432,6 +3416,15 @@ 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 svm_fpu_deactivate(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
@@ -3520,6 +3513,7 @@ 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 9055ca6..d8e23ab 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -504,7 +504,6 @@ 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;
@@ -887,7 +886,6 @@ 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)
@@ -904,14 +902,12 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
struct desc_ptr dt;
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.
@@ -922,16 +918,6 @@ 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);
- }
}
}

@@ -1160,6 +1146,12 @@ 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.
@@ -4113,6 +4105,7 @@ 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();
@@ -4352,6 +4345,7 @@ 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 36ef649..e718892 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -970,9 +970,9 @@ 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 */
@@ -1863,13 +1863,25 @@ 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);
+ kvm_request_guest_time_update(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)
--
1.7.1