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.
The patch applies on top of
'kvm: Make vcpu->requests as 64 bit bitmap'
previously sent.
Signed-off-by: Andrey Smetanin <asmetanin@xxxxxxxxxxxxx>
CC: Paolo Bonzini <pbonzini@xxxxxxxxxx>
CC: Gleb Natapov <gleb@xxxxxxxxxx>
CC: Roman Kagan <rkagan@xxxxxxxxxxxxx>
CC: Denis V. Lunev <den@xxxxxxxxxx>
CC: qemu-devel@xxxxxxxxxx
---
arch/x86/kvm/hyperv.c | 117 +++++++++++++++++++++++++++++++++++++++++------
arch/x86/kvm/hyperv.h | 2 +
arch/x86/kvm/x86.c | 12 +++++
include/linux/kvm_host.h | 1 +
4 files changed, 117 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index d50675a..504fdc7 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -753,6 +753,105 @@ static int kvm_hv_msr_set_crash_data(struct kvm_vcpu *vcpu,
return 0;
}
+static u64 calc_tsc_page_scale(u32 tsc_khz)
+{
+ /*
+ * reftime (in 100ns) = tsc * tsc_scale / 2^64 + tsc_offset
+ * so reftime_delta = (tsc_delta * tsc_scale) / 2^64
+ * so tsc_scale = (2^64 * reftime_delta)/tsc_delta
+ * so tsc_scale = (2^64 * 10 * 10^6) / tsc_hz = (2^64 * 10000) / tsc_khz
+ * so tsc_scale = (2^63 * 2 * 10000) / tsc_khz
+ */
+ return mul_u64_u32_div(1ULL << 63, 2 * 10000, tsc_khz);
+}
+
+static int write_tsc_page(struct kvm *kvm, u64 gfn,
+ PHV_REFERENCE_TSC_PAGE tsc_ref)
+{
+ if (kvm_write_guest(kvm, gfn_to_gpa(gfn),
+ tsc_ref, sizeof(*tsc_ref)))
+ return 1;
+ mark_page_dirty(kvm, gfn);
+ return 0;
+}
+
+static int read_tsc_page(struct kvm *kvm, u64 gfn,
+ PHV_REFERENCE_TSC_PAGE tsc_ref)
+{
+ if (kvm_read_guest(kvm, gfn_to_gpa(gfn),
+ tsc_ref, sizeof(*tsc_ref)))
+ return 1;
+ return 0;
+}
+
+static u64 calc_tsc_page_time(struct kvm_vcpu *vcpu,
+ PHV_REFERENCE_TSC_PAGE tsc_ref)
+{
+
+ u64 tsc = kvm_read_l1_tsc(vcpu, rdtsc());
+
+ return mul_u64_u64_shr(tsc, tsc_ref->tsc_scale, 64)
+ + tsc_ref->tsc_offset;
+}
+
+static int setup_blank_tsc_page(struct kvm_vcpu *vcpu, u64 gfn)
+{
+ HV_REFERENCE_TSC_PAGE tsc_ref;
+
+ memset(&tsc_ref, 0, sizeof(tsc_ref));
+ return write_tsc_page(vcpu->kvm, gfn, &tsc_ref);
+}
+
+int kvm_hv_setup_tsc_page(struct kvm_vcpu *vcpu)
+{
+ struct kvm *kvm = vcpu->kvm;
+ struct kvm_hv *hv = &kvm->arch.hyperv;
+ HV_REFERENCE_TSC_PAGE tsc_ref;
+ u32 tsc_khz;
+ int r;
+ u64 gfn, ref_time, tsc_scale, tsc_offset, tsc;
+
+ if (WARN_ON_ONCE(!(hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE)))
+ return -EINVAL;
+
+ gfn = hv->hv_tsc_page >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT;
+ vcpu_debug(vcpu, "tsc page gfn 0x%llx\n", gfn);
+
+ tsc_khz = vcpu->arch.virtual_tsc_khz;
+ if (!tsc_khz) {
+ vcpu_unimpl(vcpu, "no tsc khz\n");
+ return setup_blank_tsc_page(vcpu, gfn);
+ }
+
+ r = read_tsc_page(kvm, gfn, &tsc_ref);
+ if (r) {
+ vcpu_err(vcpu, "can't access tsc page gfn 0x%llx\n", gfn);
+ return r;
+ }
+
+ tsc_scale = calc_tsc_page_scale(tsc_khz);
+ ref_time = get_time_ref_counter(kvm);
+ tsc = kvm_read_l1_tsc(vcpu, rdtsc());
+
+ /* tsc_offset = reftime - tsc * tsc_scale / 2^64 */
+ tsc_offset = ref_time - mul_u64_u64_shr(tsc, tsc_scale, 64);
+ vcpu_debug(vcpu, "tsc khz %u tsc %llu scale %llu offset %llu\n",
+ tsc_khz, tsc, tsc_scale, tsc_offset);
+
+ tsc_ref.tsc_sequence++;
+ if (tsc_ref.tsc_sequence == 0)
+ tsc_ref.tsc_sequence = 1;
+
+ tsc_ref.tsc_scale = tsc_scale;
+ tsc_ref.tsc_offset = tsc_offset;
+
+ vcpu_debug(vcpu, "tsc page calibration time %llu vs. reftime %llu\n",
+ calc_tsc_page_time(vcpu, &tsc_ref),
+ get_time_ref_counter(kvm));
+
+ return write_tsc_page(kvm, gfn, &tsc_ref);
+}
+
static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
bool host)
{
@@ -790,23 +889,11 @@ 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_HV_TSC_PAGE, 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,
diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 60eccd4..e7cc446 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -84,4 +84,6 @@ static inline bool kvm_hv_has_stimer_pending(struct kvm_vcpu *vcpu)
void kvm_hv_process_stimers(struct kvm_vcpu *vcpu);
+int kvm_hv_setup_tsc_page(struct kvm_vcpu *vcpu);
+
#endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index aedb1a0..1d821f6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6500,6 +6500,18 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
*/
if (kvm_check_request(KVM_REQ_HV_STIMER, vcpu))
kvm_hv_process_stimers(vcpu);
+
+ /*
+ * KVM_REQ_HV_TSC_PAGE setup should be after
+ * KVM_REQ_CLOCK_UPDATE processing because
+ * Hyper-V tsc page content depends
+ * on kvm->arch.kvmclock_offset value.
+ */
+ if (kvm_check_request(KVM_REQ_HV_TSC_PAGE, vcpu)) {
+ r = kvm_hv_setup_tsc_page(vcpu);
+ if (unlikely(r))
+ goto out;
+ }
}
/*
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6877b4d7e..93c9e25 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -145,6 +145,7 @@ static inline bool is_error_page(struct page *page)
#define KVM_REQ_HV_RESET 29
#define KVM_REQ_HV_EXIT 30
#define KVM_REQ_HV_STIMER 31
+#define KVM_REQ_HV_TSC_PAGE 32
#define KVM_REQ_MAX 64
