Re: [PATCH] spapr: Add "memop" hypercall

[Avi Kivity <avi@redhat.com>]

On 05/21/2012 01:04 PM, Benjamin Herrenschmidt wrote:
> On Mon, 2012-05-21 at 12:47 +0300, Avi Kivity wrote:
> > On 05/21/2012 10:24 AM, Benjamin Herrenschmidt wrote:
> > > This adds a kvm-specific hypervisor call to the pseries machine
> > > which allows to do what amounts to memmove, memcpy and xor over
> > > regions of physical memory such as the framebuffer.
> > >
> > > This is the simplest way to get usable framebuffer speed from
> > > SLOF since the framebuffer isn't mapped in the VRMA and so would
> > > otherwise require an hcall per 8 bytes access.
> > >
> > > The performance is still not great but usable, and can be improved
> > > with a more complex implementation of the hcall itself if needed.
> > >
> > > Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > > ---
> > >  hw/spapr.h       |    3 ++-
> > >  hw/spapr_hcall.c |   49 +++++++++++++++++++++++++++++++++++++++++++++++++
> > >  2 files changed, 51 insertions(+), 1 deletion(-)
> > >
> > 
> > Shouldn't these be documented somewhere?
>
> Hrm, that's a good point. So far we've been mostly implementing the PAPR
> spec so the documentation exists.
>
> Before that patch we only had one "special" hcall not in PAPR, which we
> use for the RTAS firmware calls (this part of the FW normally lives
> inside the guest on real pHyp and communicates with the hypervisor using
> private hcalls, on qemu, we just turn all the RTAS calls to qemu via a
> single H_RTAS multiplexer). We haven't documented it.
>
> Now I'm adding another one, so yes, it's looking like a trend :-) I'll
> look into it, at this stage with only those two, adding some comments in
> the header might be plenty enough.

Documentation/virtual/kvm/ppc-pv.txt is a nice central place for these. 
It would be even better if you could add them to the spec.


-- 
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