On Fri, Jan 17, 2014 at 10:06:00PM +1100, Vadim Rozenfeld wrote:
> On Thu, 2014-01-16 at 20:23 -0200, Marcelo Tosatti wrote:
> > On Thu, Jan 16, 2014 at 08:18:37PM +1100, Vadim Rozenfeld wrote:
> > > Signed-off: Peter Lieven <pl@xxxxxxx>
> > > Signed-off: Gleb Natapov
> > > Signed-off: Vadim Rozenfeld <vrozenfe@xxxxxxxxxx>
> > >
> > > After some consideration I decided to submit only Hyper-V reference
> > > counters support this time. I will submit iTSC support as a separate
> > > patch as soon as it is ready.
> > >
> > > v1 -> v2
> > > 1. mark TSC page dirty as suggested by
> > > Eric Northup <digitaleric@xxxxxxxxxx> and Gleb
> > > 2. disable local irq when calling get_kernel_ns,
> > > as it was done by Peter Lieven <pl@xxxxxx>
> > > 3. move check for TSC page enable from second patch
> > > to this one.
> > >
> > > v3 -> v4
> > > Get rid of ref counter offset.
> > >
> > > v4 -> v5
> > > replace __copy_to_user with kvm_write_guest
> > > when updateing iTSC page.
> > >
> > > ---
> > > arch/x86/include/asm/kvm_host.h | 1 +
> > > arch/x86/include/uapi/asm/hyperv.h | 13 +++++++++++++
> > > arch/x86/kvm/x86.c | 28 +++++++++++++++++++++++++++-
> > > include/uapi/linux/kvm.h | 1 +
> > > 4 files changed, 42 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > > index ae5d783..33fef07 100644
> > > --- a/arch/x86/include/asm/kvm_host.h
> > > +++ b/arch/x86/include/asm/kvm_host.h
> > > @@ -605,6 +605,7 @@ struct kvm_arch {
> > > /* fields used by HYPER-V emulation */
> > > u64 hv_guest_os_id;
> > > u64 hv_hypercall;
> > > + 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 b8f1c01..462efe7 100644
> > > --- a/arch/x86/include/uapi/asm/hyperv.h
> > > +++ b/arch/x86/include/uapi/asm/hyperv.h
> > > @@ -28,6 +28,9 @@
> > > /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
> > > #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE (1 << 1)
> > >
> > > +/* A partition's reference time stamp counter (TSC) page */
> > > +#define HV_X64_MSR_REFERENCE_TSC 0x40000021
> > > +
> > > /*
> > > * There is a single feature flag that signifies the presence of the MSR
> > > * that can be used to retrieve both the local APIC Timer frequency as
> > > @@ -198,6 +201,9 @@
> > > #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_MASK \
> > > (~((1ull << HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT) - 1))
> > >
> > > +#define HV_X64_MSR_TSC_REFERENCE_ENABLE 0x00000001
> > > +#define HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT 12
> > > +
> > > #define HV_PROCESSOR_POWER_STATE_C0 0
> > > #define HV_PROCESSOR_POWER_STATE_C1 1
> > > #define HV_PROCESSOR_POWER_STATE_C2 2
> > > @@ -210,4 +216,11 @@
> > > #define HV_STATUS_INVALID_ALIGNMENT 4
> > > #define HV_STATUS_INSUFFICIENT_BUFFERS 19
> > >
> > > +typedef struct _HV_REFERENCE_TSC_PAGE {
> > > + __u32 tsc_sequence;
> > > + __u32 res1;
> > > + __u64 tsc_scale;
> > > + __s64 tsc_offset;
> > > +} HV_REFERENCE_TSC_PAGE, *PHV_REFERENCE_TSC_PAGE;
> > > +
> > > #endif
> > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > > index 5d004da..8e685b8 100644
> > > --- a/arch/x86/kvm/x86.c
> > > +++ b/arch/x86/kvm/x86.c
> > > @@ -836,11 +836,12 @@ EXPORT_SYMBOL_GPL(kvm_rdpmc);
> > > * kvm-specific. Those are put in the beginning of the list.
> > > */
> > >
> > > -#define KVM_SAVE_MSRS_BEGIN 10
> > > +#define KVM_SAVE_MSRS_BEGIN 12
> > > 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_TIME_REF_COUNT, HV_X64_MSR_REFERENCE_TSC,
> > > 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,
> > > @@ -1826,6 +1827,8 @@ 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;
> > > }
> > > @@ -1867,6 +1870,20 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> > > kvm->arch.hv_hypercall = data;
> > > break;
> > > }
> > > + case HV_X64_MSR_REFERENCE_TSC: {
> > > + u64 gfn;
> > > + HV_REFERENCE_TSC_PAGE tsc_ref;
> > > + memset(&tsc_ref, 0, sizeof(tsc_ref));
> > > + kvm->arch.hv_tsc_page = data;
> >
> > Comment 1)
> >
> > Is there a reason (that is compliance with spec) to maintain
> > value, for HV_X64_MSR_REFERENCE_TSC wrmsr operation, in case
> > HV_X64_MSR_TSC_REFERENCE_ENABLE is not set?
>
> Windows seems to be retrieving HV_X64_MSR_REFERENCE_TSC value only once
> on boot-up, checks HV_X64_MSR_TSC_REFERENCE_ENABLE bit allocate one page
> and maps it into the system space, and writes the page address to
> HV_X64_MSR_REFERENCE_TSC MSR if this bit was not set. Windows keeps the
> TSC page address value in HvlReferenceTscPage variable and uses it
> every time when needs to read the TSC page content.
Ok then it has to be saved/restored irrespective of the value of
HV_X64_MSR_TSC_REFERENCE_ENABLE.
> > If not, should only assign to kvm->arch.hv_tsc_page after proper checks.
> >
> > > + if (!(data & HV_X64_MSR_TSC_REFERENCE_ENABLE))
> > > + break;
> > > + gfn = data >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT;
> > > + if (kvm_write_guest(kvm, data,
> > > + &tsc_ref, sizeof(tsc_ref)))
> > > + return 1;
> > > + mark_page_dirty(kvm, gfn);
> > > + break;
> > > + }
> > > default:
> > > vcpu_unimpl(vcpu, "HYPER-V unimplemented wrmsr: 0x%x "
> > > "data 0x%llx\n", msr, data);
> > > @@ -2291,6 +2308,14 @@ 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.kvmclock_offset, 100);
> >
> > Comment 2)
> >
> > Is there any specification related to the initial value of the clock
> > after it is enabled ?
>
> The MS documentation says the following:
> "A partition's reference time counter is initialized to zero when the
> partition is created. The reference time counter for all partitions
> count at the same rate. However, at any time, the absolute value of each
> reference time counter will typically differ because partitions will
> have different creation times."
>
> http://msdn.microsoft.com/en-us/library/windows/hardware/ff542637%
> 28v=vs.85%29.aspx
>
> However, Windows doesn't seem to be worried about the initial value.
> HvlGetReferenceTime only reads HV_X64_MSR_TIME_REF_COUNT MSR and
> returns the obtained value.
Right. It might be better to initialize kvmclock_offset to zero
in case of VM creation (QEMU's PUT_FULL state), in case Hyper-V timers
enabled, with reference to MS docs on top.
Otherwise might end up hitting Windows code timers bugs.
But its a potential improvement, patch looks good.
> > > + }
> > > + case HV_X64_MSR_REFERENCE_TSC:
> > > + data = kvm->arch.hv_tsc_page;
> > > + break;
> > > default:
> > > vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
> > > return 1;
> > > @@ -2604,6 +2629,7 @@ int kvm_dev_ioctl_check_extension(long ext)
> > > #ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
> > > case KVM_CAP_ASSIGN_DEV_IRQ:
> > > case KVM_CAP_PCI_2_3:
> > > + case KVM_CAP_HYPERV_TIME:
> > > #endif
> > > r = 1;
> > > break;
> > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > > index 902f124..686c1ca 100644
> > > --- a/include/uapi/linux/kvm.h
> > > +++ b/include/uapi/linux/kvm.h
> > > @@ -674,6 +674,7 @@ struct kvm_ppc_smmu_info {
> > > #define KVM_CAP_ARM_EL1_32BIT 93
> > > #define KVM_CAP_SPAPR_MULTITCE 94
> > > #define KVM_CAP_EXT_EMUL_CPUID 95
> > > +#define KVM_CAP_HYPERV_TIME 96
> > >
> > > #ifdef KVM_CAP_IRQ_ROUTING
> > >
> > > --
> > > 1.8.1.4
> > >
> >
> > Comment 3)
> >
> > Missing qemu HV_X64_MSR_REFERENCE_TSC save/restore.
> I have this code ready. I'm going to send it to qemu
> list as soon as KVM patch will be accepted.
Looks good to me.
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