linux-kernel - Re: [PATCH 5/6] KVM: selftests: Move hypercall() to hyper.h

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Date:   Tue, 8 Nov 2022 09:40:09 -0800
From:   David Matlack <dmatlack@...gle.com>
To:     Vipin Sharma <vipinsh@...gle.com>
Cc:     seanjc@...gle.com, pbonzini@...hat.com, vkuznets@...hat.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] KVM: selftests: Move hypercall() to hyper.h

On Mon, Nov 7, 2022 at 5:49 PM Vipin Sharma <vipinsh@...gle.com> wrote:
>
> On Mon, Nov 7, 2022 at 10:30 AM David Matlack <dmatlack@...gle.com> wrote:
> >
> > On Fri, Nov 04, 2022 at 09:57:03PM -0700, Vipin Sharma wrote:
> > > hypercall() can be used by other hyperv tests, move it to hyperv.h.
> > >
> > > Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
> > > ---
> > >  .../selftests/kvm/include/x86_64/hyperv.h       | 17 +++++++++++++++++
> > >  .../selftests/kvm/x86_64/hyperv_features.c      | 17 -----------------
> > >  2 files changed, 17 insertions(+), 17 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/kvm/include/x86_64/hyperv.h b/tools/testing/selftests/kvm/include/x86_64/hyperv.h
> > > index 9d8c325af1d9..87d8d9e444f7 100644
> > > --- a/tools/testing/selftests/kvm/include/x86_64/hyperv.h
> > > +++ b/tools/testing/selftests/kvm/include/x86_64/hyperv.h
> > > @@ -199,4 +199,21 @@ static inline uint64_t hv_linux_guest_id(void)
> > >              ((uint64_t)LINUX_VERSION_CODE << 16);
> > >  }
> > >
> > > +static inline uint8_t hypercall(u64 control, vm_vaddr_t input_address,
> > > +                             vm_vaddr_t output_address, uint64_t *hv_status)
> > > +{
> > > +     uint8_t vector;
> > > +
> > > +     /* Note both the hypercall and the "asm safe" clobber r9-r11. */
> > > +     asm volatile("mov %[output_address], %%r8\n\t"
> > > +                  KVM_ASM_SAFE("vmcall")
> > > +                  : "=a" (*hv_status),
> > > +                    "+c" (control), "+d" (input_address),
> > > +                    KVM_ASM_SAFE_OUTPUTS(vector)
> > > +                  : [output_address] "r"(output_address),
> > > +                    "a" (-EFAULT)
> > > +                  : "cc", "memory", "r8", KVM_ASM_SAFE_CLOBBERS);
> > > +     return vector;
> > > +}
> >
> > Since this function is Hyper-V specific it probably makes sense to
> > rename it to hyperv_hypercall() as part of moving it to library, e.g. to
> > differentiate it from kvm_hypercall().
> >
>
> Sounds good. Does it keeping it in header file "hyperv.h" seems fine
> or should I create a new "hyperv.c" lib file and move function
> definition there?

I think it's fine to keep in hyperv.h. It seems like the type of
function we'd want to be inlined anyway, and the implementation is
short.