On Tue, May 14, 2013 at 07:46:36PM +1000, Vadim Rozenfeld wrote:
> On Mon, 2013-05-13 at 16:30 -0700, Eric Northup wrote:
> > On Mon, May 13, 2013 at 4:45 AM, Vadim Rozenfeld <[email protected]>
> > wrote:
> > > Signed-off: Peter Lieven <[email protected]>
> > > Signed-off: Gleb Natapov <[email protected]>
> > > Signed-off: Vadim Rozenfeld <[email protected]>
> > >
> > > 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)))
> >
> > Does this do the right thing when we're migrating? How does usermode
> > learn that the guest page has been dirtied?
> >
>
> No, it shouldn't be a problem for this patch. Guest allocates a page
> from nonpaged physical memory, maps it to the system address space, gets
> physical address and sends it to KVM. KVM sets the first DWORD
> (TscSequence) to zero, which means that guest will use reference time
> counter as a timestamp source even after migration.
>
Eric is right, we need mark_page_dirty() here and in HV_X64_MSR_HYPERCALL
too. Without it QEMU will not know that content of the page has changed
and will not migrate it.
--
Gleb.
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