Create an infrastructure for tracking Hyper-V TSC page status, i.e. if it
was updated from guest/host side or if we've failed to set it up (because
e.g. guest wrote some garbage to HV_X64_MSR_REFERENCE_TSC) and there's no
need to retry.
Also, in a hypothetical situation when we are in 'always catchup' mode for
TSC we can now avoid contending 'hv->hv_lock' on every guest enter by
setting the state to HV_TSC_PAGE_BROKEN after compute_tsc_page_parameters()
returns false.
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 9 +++++++++
arch/x86/kvm/hyperv.c | 23 +++++++++++++++++------
2 files changed, 26 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9bc091ecaaeb..87448e9e6b28 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -884,12 +884,21 @@ struct kvm_hv_syndbg {
u64 options;
};
+enum hv_tsc_page_status {
+ HV_TSC_PAGE_UNSET = 0,
+ HV_TSC_PAGE_GUEST_CHANGED,
+ HV_TSC_PAGE_HOST_CHANGED,
+ HV_TSC_PAGE_SET,
+ HV_TSC_PAGE_BROKEN,
+};
+
/* Hyper-V emulation context */
struct kvm_hv {
struct mutex hv_lock;
u64 hv_guest_os_id;
u64 hv_hypercall;
u64 hv_tsc_page;
+ enum hv_tsc_page_status hv_tsc_page_status;
/* Hyper-v based guest crash (NT kernel bugcheck) parameters */
u64 hv_crash_param[HV_X64_MSR_CRASH_PARAMS];
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index eefb85b86fe8..2a8d078b16cb 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1087,7 +1087,7 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm,
BUILD_BUG_ON(sizeof(tsc_seq) != sizeof(hv->tsc_ref.tsc_sequence));
BUILD_BUG_ON(offsetof(struct ms_hyperv_tsc_page, tsc_sequence) != 0);
- if (!(hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE))
+ if (hv->hv_tsc_page_status == HV_TSC_PAGE_BROKEN)
return;
mutex_lock(&hv->hv_lock);
@@ -1101,7 +1101,7 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm,
*/
if (unlikely(kvm_read_guest(kvm, gfn_to_gpa(gfn),
&tsc_seq, sizeof(tsc_seq))))
- goto out_unlock;
+ goto out_err;
/*
* While we're computing and writing the parameters, force the
@@ -1110,15 +1110,15 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm,
hv->tsc_ref.tsc_sequence = 0;
if (kvm_write_guest(kvm, gfn_to_gpa(gfn),
&hv->tsc_ref, sizeof(hv->tsc_ref.tsc_sequence)))
- goto out_unlock;
+ goto out_err;
if (!compute_tsc_page_parameters(hv_clock, &hv->tsc_ref))
- goto out_unlock;
+ goto out_err;
/* 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)))
- goto out_unlock;
+ goto out_err;
/*
* Now switch to the TSC page mechanism by writing the sequence.
@@ -1133,6 +1133,12 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm,
hv->tsc_ref.tsc_sequence = tsc_seq;
kvm_write_guest(kvm, gfn_to_gpa(gfn),
&hv->tsc_ref, sizeof(hv->tsc_ref.tsc_sequence));
+
+ hv->hv_tsc_page_status = HV_TSC_PAGE_SET;
+ goto out_unlock;
+
+out_err:
+ hv->hv_tsc_page_status = HV_TSC_PAGE_BROKEN;
out_unlock:
mutex_unlock(&hv->hv_lock);
}
@@ -1193,8 +1199,13 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
}
case HV_X64_MSR_REFERENCE_TSC:
hv->hv_tsc_page = data;
- if (hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE)
+ if (hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE) {
+ if (!host)
+ hv->hv_tsc_page_status = HV_TSC_PAGE_GUEST_CHANGED;
+ else
+ hv->hv_tsc_page_status = HV_TSC_PAGE_HOST_CHANGED;
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(kvm,
--
2.30.2
