Re: [RFC PATCH 1/2] Hyper-H reference counter

Vadim Rozenfeld
2013-05-15T10:24:25Z

On Tue, 2013-05-14 at 16:14 +0200, Peter Lieven wrote:
> On 13.05.2013 13:45, Vadim Rozenfeld wrote:
> > Signed-off: Peter Lieven <pl@dlh.net>
> > Signed-off: Gleb Natapov <gleb@redhat.com>
> > Signed-off: Vadim Rozenfeld <vrozenfe@redhat.com>
> >
> > The following patch allows to activate Hyper-V
> > reference time counter
> > ---
> > arch/x86/include/asm/kvm_host.h | 2 ++
> > arch/x86/include/uapi/asm/hyperv.h | 3 +++
> > arch/x86/kvm/x86.c | 25 ++++++++++++++++++++++++-
> > 3 files changed, 29 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 3741c65..f0fee35 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -575,6 +575,8 @@ struct kvm_arch {
> > /* fields used by HYPER-V emulation */
> > u64 hv_guest_os_id;
> > u64 hv_hypercall;
> > + u64 hv_ref_count;
> > + u64 hv_tsc_page;
> >
> > #ifdef CONFIG_KVM_MMU_AUDIT
> > int audit_point;
> > diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
> > index b80420b..9711819 100644
> > --- a/arch/x86/include/uapi/asm/hyperv.h
> > +++ b/arch/x86/include/uapi/asm/hyperv.h
> > @@ -136,6 +136,9 @@
> > /* MSR used to read the per-partition time reference counter */
> > #define HV_X64_MSR_TIME_REF_COUNT 0x40000020
> >
> > +/* A partition's reference time stamp counter (TSC) page */
> > +#define HV_X64_MSR_REFERENCE_TSC 0x40000021
> > +
> > /* Define the virtual APIC registers */
> > #define HV_X64_MSR_EOI 0x40000070
> > #define HV_X64_MSR_ICR 0x40000071
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 094b5d9..1a4036d 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -843,7 +843,7 @@ EXPORT_SYMBOL_GPL(kvm_rdpmc);
> > static u32 msrs_to_save[] = {
> > MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
> > MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
> > - HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
> > + HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,HV_X64_MSR_TIME_REF_COUNT,
> > HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
> > MSR_KVM_PV_EOI_EN,
> > MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
> > @@ -1764,6 +1764,8 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
> > switch (msr) {
> > case HV_X64_MSR_GUEST_OS_ID:
> > case HV_X64_MSR_HYPERCALL:
> > + case HV_X64_MSR_REFERENCE_TSC:
> > + case HV_X64_MSR_TIME_REF_COUNT:
> > r = true;
> > break;
> > }
> > @@ -1803,6 +1805,21 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> > if (__copy_to_user((void __user *)addr, instructions, 4))
> > return 1;
> > kvm->arch.hv_hypercall = data;
> > + kvm->arch.hv_ref_count = get_kernel_ns();
> > + break;
> > + }
> > + case HV_X64_MSR_REFERENCE_TSC: {
> > + u64 gfn;
> > + unsigned long addr;
> > + u32 tsc_ref;
> > + gfn = data >> HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT;
> > + addr = gfn_to_hva(kvm, gfn);
> > + if (kvm_is_error_hva(addr))
> > + return 1;
> > + tsc_ref = 0;
> > + if(__copy_to_user((void __user *)addr, &tsc_ref, sizeof(tsc_ref)))
> > + return 1;
> > + kvm->arch.hv_tsc_page = data;
> > break;
> > }
> > default:
> > @@ -2229,6 +2246,12 @@ static int get_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
> > case HV_X64_MSR_HYPERCALL:
> > data = kvm->arch.hv_hypercall;
> > break;
> > + case HV_X64_MSR_TIME_REF_COUNT:
> > + data = div_u64(get_kernel_ns() - kvm->arch.hv_ref_count,100);
> > + break;
>
>
> in an earlier version of this patch I have the following:
>
> + case HV_X64_MSR_TIME_REF_COUNT: {
> + u64 now_ns;
> + local_irq_disable();
> + now_ns = get_kernel_ns();
> + data = div_u64(now_ns + kvm->arch.kvmclock_offset - kvm->arch.hv_ref_count,100);
> + local_irq_enable();
> + break;
> + }
>
> I do not know if this is right, but I can report that this one is working without any flaws
> since approx. 1.5 years.

Hi Peter,
I created this patch based on the original code posted
in thread http://marc.info/?l=kvm&m=133278705514826
But please feel free to send your version, if you see any problem
in the current code.
Best regards,
Vadim.

> Peter