Re: [PATCH v1 3/3] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls

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On Wed, Mar 4, 2020 at 4:00 PM Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote:
>
> Jon Doron <arilou@xxxxxxxxx> writes:
>
> > There is another mode for the synthetic debugger which uses hypercalls
> > to send/recv network data instead of the MSR interface.
> >
> > This interface is much slower and less recommended since you might get
> > a lot of VMExits while KDVM polling for new packets to recv, rather
> > than simply checking the pending page to see if there is data avialble
> > and then request.
> >
> > Signed-off-by: Jon Doron <arilou@xxxxxxxxx>
> > ---
> >  arch/x86/include/asm/hyperv-tlfs.h |  5 +++++
> >  arch/x86/kvm/hyperv.c              | 11 +++++++++++
> >  2 files changed, 16 insertions(+)
> >
> > diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> > index 8efdf974c23f..4fa6bf3732a6 100644
> > --- a/arch/x86/include/asm/hyperv-tlfs.h
> > +++ b/arch/x86/include/asm/hyperv-tlfs.h
> > @@ -283,6 +283,8 @@
> >  #define HV_X64_MSR_SYNDBG_PENDING_BUFFER     0x400000F5
> >  #define HV_X64_MSR_SYNDBG_OPTIONS            0x400000FF
> >
> > +#define HV_X64_SYNDBG_OPTION_USE_HCALLS              BIT(2)
> > +
>
> BIT(2) of what? :-) Also, you don't seem to use this define anywhere.
>

Will use it now :) and it's a syndbg MSR option bit

> >  /* Hyper-V guest crash notification MSR's */
> >  #define HV_X64_MSR_CRASH_P0                  0x40000100
> >  #define HV_X64_MSR_CRASH_P1                  0x40000101
> > @@ -392,6 +394,9 @@ struct hv_tsc_emulation_status {
> >  #define HVCALL_SEND_IPI_EX                   0x0015
> >  #define HVCALL_POST_MESSAGE                  0x005c
> >  #define HVCALL_SIGNAL_EVENT                  0x005d
> > +#define HVCALL_POST_DEBUG_DATA                       0x0069
> > +#define HVCALL_RETRIEVE_DEBUG_DATA           0x006a
> > +#define HVCALL_RESET_DEBUG_SESSION           0x006b
> >  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
> >  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
> >
> > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> > index 7ec962d433af..593e0f3f4dba 100644
> > --- a/arch/x86/kvm/hyperv.c
> > +++ b/arch/x86/kvm/hyperv.c
> > @@ -1794,6 +1794,17 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
> >               }
> >               ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, true, false);
> >               break;
> > +     case HVCALL_POST_DEBUG_DATA:
> > +     case HVCALL_RETRIEVE_DEBUG_DATA:
> > +     case HVCALL_RESET_DEBUG_SESSION:
> > +             vcpu->run->exit_reason = KVM_EXIT_HYPERV;
> > +             vcpu->run->hyperv.type = KVM_EXIT_HYPERV_HCALL;
> > +             vcpu->run->hyperv.u.hcall.input = param;
> > +             vcpu->run->hyperv.u.hcall.params[0] = ingpa;
> > +             vcpu->run->hyperv.u.hcall.params[1] = outgpa;
> > +             vcpu->arch.complete_userspace_io =
> > +                             kvm_hv_hypercall_complete_userspace;
> > +             return 0;
> >       default:
> >               ret = HV_STATUS_INVALID_HYPERCALL_CODE;
> >               break;
>
> --
> Vitaly
>



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