KVM: x86: Hyper-V tsc page setup
Lately tsc page was implemented but filled with empty values. This patch setup tsc page scale and offset based on vcpu tsc, tsc_khz and HV_X64_MSR_TIME_REF_COUNT value. The valid tsc page drops HV_X64_MSR_TIME_REF_COUNT msr reads count to zero which potentially improves performance. Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com> Reviewed-by: Peter Hornyack <peterhornyack@google.com> Reviewed-by: Radim Krčmář <rkrcmar@redhat.com> CC: Paolo Bonzini <pbonzini@redhat.com> CC: Roman Kagan <rkagan@virtuozzo.com> CC: Denis V. Lunev <den@openvz.org> [Computation of TSC page parameters rewritten to use the Linux timekeeper parameters. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>hifive-unleashed-5.1
Paolo Bonzini
parent
108b249c45
commit
095cf55df7
|
|
@ -702,6 +702,8 @@ struct kvm_hv {
|
|||
/* Hyper-v based guest crash (NT kernel bugcheck) parameters */
|
||||
u64 hv_crash_param[HV_X64_MSR_CRASH_PARAMS];
|
||||
u64 hv_crash_ctl;
|
||||
|
||||
HV_REFERENCE_TSC_PAGE tsc_ref;
|
||||
};
|
||||
|
||||
struct kvm_arch {
|
||||
|
|
|
|||
|
|
@ -386,7 +386,21 @@ static void synic_init(struct kvm_vcpu_hv_synic *synic)
|
|||
|
||||
static u64 get_time_ref_counter(struct kvm *kvm)
|
||||
{
|
||||
return div_u64(get_kvmclock_ns(kvm), 100);
|
||||
struct kvm_hv *hv = &kvm->arch.hyperv;
|
||||
struct kvm_vcpu *vcpu;
|
||||
u64 tsc;
|
||||
|
||||
/*
|
||||
* The guest has not set up the TSC page or the clock isn't
|
||||
* stable, fall back to get_kvmclock_ns.
|
||||
*/
|
||||
if (!hv->tsc_ref.tsc_sequence)
|
||||
return div_u64(get_kvmclock_ns(kvm), 100);
|
||||
|
||||
vcpu = kvm_get_vcpu(kvm, 0);
|
||||
tsc = kvm_read_l1_tsc(vcpu, rdtsc());
|
||||
return mul_u64_u64_shr(tsc, hv->tsc_ref.tsc_scale, 64)
|
||||
+ hv->tsc_ref.tsc_offset;
|
||||
}
|
||||
|
||||
static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer,
|
||||
|
|
@ -756,6 +770,129 @@ static int kvm_hv_msr_set_crash_data(struct kvm_vcpu *vcpu,
|
|||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* The kvmclock and Hyper-V TSC page use similar formulas, and converting
|
||||
* between them is possible:
|
||||
*
|
||||
* kvmclock formula:
|
||||
* nsec = (ticks - tsc_timestamp) * tsc_to_system_mul * 2^(tsc_shift-32)
|
||||
* + system_time
|
||||
*
|
||||
* Hyper-V formula:
|
||||
* nsec/100 = ticks * scale / 2^64 + offset
|
||||
*
|
||||
* When tsc_timestamp = system_time = 0, offset is zero in the Hyper-V formula.
|
||||
* By dividing the kvmclock formula by 100 and equating what's left we get:
|
||||
* ticks * scale / 2^64 = ticks * tsc_to_system_mul * 2^(tsc_shift-32) / 100
|
||||
* scale / 2^64 = tsc_to_system_mul * 2^(tsc_shift-32) / 100
|
||||
* scale = tsc_to_system_mul * 2^(32+tsc_shift) / 100
|
||||
*
|
||||
* Now expand the kvmclock formula and divide by 100:
|
||||
* nsec = ticks * tsc_to_system_mul * 2^(tsc_shift-32)
|
||||
* - tsc_timestamp * tsc_to_system_mul * 2^(tsc_shift-32)
|
||||
* + system_time
|
||||
* nsec/100 = ticks * tsc_to_system_mul * 2^(tsc_shift-32) / 100
|
||||
* - tsc_timestamp * tsc_to_system_mul * 2^(tsc_shift-32) / 100
|
||||
* + system_time / 100
|
||||
*
|
||||
* Replace tsc_to_system_mul * 2^(tsc_shift-32) / 100 by scale / 2^64:
|
||||
* nsec/100 = ticks * scale / 2^64
|
||||
* - tsc_timestamp * scale / 2^64
|
||||
* + system_time / 100
|
||||
*
|
||||
* Equate with the Hyper-V formula so that ticks * scale / 2^64 cancels out:
|
||||
* offset = system_time / 100 - tsc_timestamp * scale / 2^64
|
||||
*
|
||||
* These two equivalencies are implemented in this function.
|
||||
*/
|
||||
static bool compute_tsc_page_parameters(struct pvclock_vcpu_time_info *hv_clock,
|
||||
HV_REFERENCE_TSC_PAGE *tsc_ref)
|
||||
{
|
||||
u64 max_mul;
|
||||
|
||||
if (!(hv_clock->flags & PVCLOCK_TSC_STABLE_BIT))
|
||||
return false;
|
||||
|
||||
/*
|
||||
* check if scale would overflow, if so we use the time ref counter
|
||||
* tsc_to_system_mul * 2^(tsc_shift+32) / 100 >= 2^64
|
||||
* tsc_to_system_mul / 100 >= 2^(32-tsc_shift)
|
||||
* tsc_to_system_mul >= 100 * 2^(32-tsc_shift)
|
||||
*/
|
||||
max_mul = 100ull << (32 - hv_clock->tsc_shift);
|
||||
if (hv_clock->tsc_to_system_mul >= max_mul)
|
||||
return false;
|
||||
|
||||
/*
|
||||
* Otherwise compute the scale and offset according to the formulas
|
||||
* derived above.
|
||||
*/
|
||||
tsc_ref->tsc_scale =
|
||||
mul_u64_u32_div(1ULL << (32 + hv_clock->tsc_shift),
|
||||
hv_clock->tsc_to_system_mul,
|
||||
100);
|
||||
|
||||
tsc_ref->tsc_offset = hv_clock->system_time;
|
||||
do_div(tsc_ref->tsc_offset, 100);
|
||||
tsc_ref->tsc_offset -=
|
||||
mul_u64_u64_shr(hv_clock->tsc_timestamp, tsc_ref->tsc_scale, 64);
|
||||
return true;
|
||||
}
|
||||
|
||||
void kvm_hv_setup_tsc_page(struct kvm *kvm,
|
||||
struct pvclock_vcpu_time_info *hv_clock)
|
||||
{
|
||||
struct kvm_hv *hv = &kvm->arch.hyperv;
|
||||
u32 tsc_seq;
|
||||
u64 gfn;
|
||||
|
||||
BUILD_BUG_ON(sizeof(tsc_seq) != sizeof(hv->tsc_ref.tsc_sequence));
|
||||
BUILD_BUG_ON(offsetof(HV_REFERENCE_TSC_PAGE, tsc_sequence) != 0);
|
||||
|
||||
if (!(hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE))
|
||||
return;
|
||||
|
||||
gfn = hv->hv_tsc_page >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT;
|
||||
/*
|
||||
* Because the TSC parameters only vary when there is a
|
||||
* change in the master clock, do not bother with caching.
|
||||
*/
|
||||
if (unlikely(kvm_read_guest(kvm, gfn_to_gpa(gfn),
|
||||
&tsc_seq, sizeof(tsc_seq))))
|
||||
return;
|
||||
|
||||
/*
|
||||
* While we're computing and writing the parameters, force the
|
||||
* guest to use the time reference count MSR.
|
||||
*/
|
||||
hv->tsc_ref.tsc_sequence = 0;
|
||||
if (kvm_write_guest(kvm, gfn_to_gpa(gfn),
|
||||
&hv->tsc_ref, sizeof(hv->tsc_ref.tsc_sequence)))
|
||||
return;
|
||||
|
||||
if (!compute_tsc_page_parameters(hv_clock, &hv->tsc_ref))
|
||||
return;
|
||||
|
||||
/* Ensure sequence is zero before writing the rest of the struct. */
|
||||
smp_wmb();
|
||||
if (kvm_write_guest(kvm, gfn_to_gpa(gfn), &hv->tsc_ref, sizeof(hv->tsc_ref)))
|
||||
return;
|
||||
|
||||
/*
|
||||
* Now switch to the TSC page mechanism by writing the sequence.
|
||||
*/
|
||||
tsc_seq++;
|
||||
if (tsc_seq == 0xFFFFFFFF || tsc_seq == 0)
|
||||
tsc_seq = 1;
|
||||
|
||||
/* Write the struct entirely before the non-zero sequence. */
|
||||
smp_wmb();
|
||||
|
||||
hv->tsc_ref.tsc_sequence = tsc_seq;
|
||||
kvm_write_guest(kvm, gfn_to_gpa(gfn),
|
||||
&hv->tsc_ref, sizeof(hv->tsc_ref.tsc_sequence));
|
||||
}
|
||||
|
||||
static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
|
||||
bool host)
|
||||
{
|
||||
|
|
@ -793,23 +930,11 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
|
|||
mark_page_dirty(kvm, gfn);
|
||||
break;
|
||||
}
|
||||
case HV_X64_MSR_REFERENCE_TSC: {
|
||||
u64 gfn;
|
||||
HV_REFERENCE_TSC_PAGE tsc_ref;
|
||||
|
||||
memset(&tsc_ref, 0, sizeof(tsc_ref));
|
||||
case HV_X64_MSR_REFERENCE_TSC:
|
||||
hv->hv_tsc_page = data;
|
||||
if (!(data & HV_X64_MSR_TSC_REFERENCE_ENABLE))
|
||||
break;
|
||||
gfn = data >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT;
|
||||
if (kvm_write_guest(
|
||||
kvm,
|
||||
gfn << HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT,
|
||||
&tsc_ref, sizeof(tsc_ref)))
|
||||
return 1;
|
||||
mark_page_dirty(kvm, gfn);
|
||||
if (hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE)
|
||||
kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
|
||||
break;
|
||||
}
|
||||
case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
|
||||
return kvm_hv_msr_set_crash_data(vcpu,
|
||||
msr - HV_X64_MSR_CRASH_P0,
|
||||
|
|
|
|||
|
|
@ -84,4 +84,7 @@ static inline bool kvm_hv_has_stimer_pending(struct kvm_vcpu *vcpu)
|
|||
|
||||
void kvm_hv_process_stimers(struct kvm_vcpu *vcpu);
|
||||
|
||||
void kvm_hv_setup_tsc_page(struct kvm *kvm,
|
||||
struct pvclock_vcpu_time_info *hv_clock);
|
||||
|
||||
#endif
|
||||
|
|
|
|||
|
|
@ -1887,10 +1887,10 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
|
|||
|
||||
vcpu->hv_clock.flags = pvclock_flags;
|
||||
|
||||
if (!vcpu->pv_time_enabled)
|
||||
return 0;
|
||||
|
||||
kvm_setup_pvclock_page(v);
|
||||
if (vcpu->pv_time_enabled)
|
||||
kvm_setup_pvclock_page(v);
|
||||
if (v == kvm_get_vcpu(v->kvm, 0))
|
||||
kvm_hv_setup_tsc_page(v->kvm, &vcpu->hv_clock);
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue