Re: [RFC v2 11/14] linux-headers/kvm.h: add capability to forward hypercall

[Guoheyi]

On 2019/11/7 20:12, Cornelia Huck wrote:
> On Thu, 7 Nov 2019 19:57:22 +0800
> Guoheyi <address@hidden> wrote:
>
> > On 2019/11/7 16:57, Michael S. Tsirkin wrote:
> > > On Thu, Nov 07, 2019 at 09:44:36AM +0800, Guoheyi wrote:
> > > > On 2019/11/7 1:55, Cornelia Huck wrote:
> > > > > On Tue, 5 Nov 2019 17:10:53 +0800
> > > > > Heyi Guo <address@hidden> wrote:
> > > > >   
> > > > > > To keep backward compatibility, we add new KVM capability
> > > > > > "KVM_CAP_FORWARD_HYPERCALL" to probe whether KVM supports forwarding
> > > > > > hypercall to userspace.
> > > > > >
> > > > > > The capability should be enabled explicitly, for we don't want user
> > > > > > space application to deal with unexpected hypercall exits. After
> > > > > > enabling this cap, all HVC calls unhandled by kvm will be forwarded to
> > > > > > user space.
> > > > > >
> > > > > > Signed-off-by: Heyi Guo <address@hidden>
> > > > > > Cc: Peter Maydell <address@hidden>
> > > > > > Cc: "Michael S. Tsirkin" <address@hidden>
> > > > > > Cc: Cornelia Huck <address@hidden>
> > > > > > Cc: Paolo Bonzini <address@hidden>
> > > > > > Cc: Dave Martin <address@hidden>
> > > > > > Cc: Marc Zyngier <address@hidden>
> > > > > > Cc: Mark Rutland <address@hidden>
> > > > > > Cc: James Morse <address@hidden>
> > > > > > ---
> > > > > >     linux-headers/linux/kvm.h |  1 +
> > > > > >     target/arm/sdei.c         | 16 ++++++++++++++++
> > > > > >     target/arm/sdei.h         |  2 ++
> > > > > >     3 files changed, 19 insertions(+)
> > > > > >
> > > > > > diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
> > > > > > index 3d9b18f7f8..36c9b3859f 100644
> > > > > > --- a/linux-headers/linux/kvm.h
> > > > > > +++ b/linux-headers/linux/kvm.h
> > > > > > @@ -1000,6 +1000,7 @@ struct kvm_ppc_resize_hpt {
> > > > > >     #define KVM_CAP_PMU_EVENT_FILTER 173
> > > > > >     #define KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 174
> > > > > >     #define KVM_CAP_HYPERV_DIRECT_TLBFLUSH 175
> > > > > > +#define KVM_CAP_FORWARD_HYPERCALL 176
> > > > > >     #ifdef KVM_CAP_IRQ_ROUTING
> > > > > Is this cap upstream already? I would have thought your header sync
> > > > > would have brought it in, then. (Saying this, that header sync looks
> > > > > awfully small.)
> > > > >
> > > > > If it is not upstream yet, please split off this hunk into a separate
> > > > > patch -- it's a bit annoying, but makes life easier for merging.
> > > > No, it is not upstream yet. The whole framework and interfaces between KVM
> > > > and qemu are still under discussion. I'll keep in mind of this when moving
> > > > forward to next steps...
> > > >
> > > > Thanks,
> > > > HG
> > > It's best to add it in some other place meanwhile.
> > Do you mean to split this patch from the whole patch set and send it
> > separately? Sorry I'm not clear about maintainers' work and may bring
> > you some trouble...
> My preferred approach:
>
> - add a commit entitled "placeholder for headers update" that contains
>    the not-yet-upstream changes in the header files you need
> - base the rest of your work on that
> ...
> <review happens, series looks good>
> ...
> - if kernel changes are upstream: replace the placeholder patch with a
>    real update (may include separate patches, if you need an additional
>    header); maintainer merges
> - if kernel changes are not yet upstream: maintainer merges with
>    placeholder to a feature branch, replaces with real update and merges
>    once kernel patches hit upstream
> (not every maintainer does the second approach; they may ask you
> instead to resend with a proper headers update once the kernel changes
> are upstream)

Thanks a lot. I'll do that in the next version.
HG

> .