Re: [Qemu-devel] [PATCH 2/3] xenfb: Add option to use grant ref for shared page.

[Stefano Stabellini]

On Thu, 11 Sep 2014, Owen Smith wrote:
> > -----Original Message-----
> > From: Stefano Stabellini [mailto:address@hidden
> > Sent: 11 September 2014 02:01
> > To: Owen Smith
> > Cc: address@hidden; address@hidden; Stefano Stabellini
> > Subject: Re: [PATCH 2/3] xenfb: Add option to use grant ref for shared page.
> > 
> > On Wed, 10 Sep 2014, Owen smith wrote:
> > > The vkbd device should be able to use a grant reference to map the
> > > shared page.
> > >
> > > Signed-off-by: Owen smith <address@hidden>
> > > ---
> > >  hw/display/xenfb.c | 39 +++++++++++++++++++++++++++++----------
> > >  1 file changed, 29 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c index
> > > 2c39753..c4375c8 100644
> > > --- a/hw/display/xenfb.c
> > > +++ b/hw/display/xenfb.c
> > > @@ -54,6 +54,7 @@
> > >  struct common {
> > >      struct XenDevice  xendev;  /* must be first */
> > >      void              *page;
> > > +    int               page_gref;
> > >      QemuConsole       *con;
> > >  };
> > >
> > > @@ -96,22 +97,36 @@ static int common_bind(struct common *c)  {
> > >      uint64_t mfn;
> > >
> > > -    if (xenstore_read_fe_uint64(&c->xendev, "page-ref", &mfn) == -1)
> > > - return -1;
> > > -    assert(mfn == (xen_pfn_t)mfn);
> > > -
> > >      if (xenstore_read_fe_int(&c->xendev, "event-channel", &c-
> > >xendev.remote_port) == -1)
> > >   return -1;
> > >
> > > -    c->page = xc_map_foreign_range(xen_xc, c->xendev.dom,
> > > -                            XC_PAGE_SIZE,
> > > -                            PROT_READ | PROT_WRITE, mfn);
> > > +    if (xenstore_read_fe_uint64(&c->xendev, "page-ref", &mfn) == -1) {
> > > +        if (xenstore_read_fe_int(&c->xendev, "page-gref", &c->page_gref)
> > == -1) {
> > > +            return -1;
> > > +        }
> > > +        c->page = xc_gnttab_map_grant_ref(c->xendev.gnttabdev,
> > > +                                          c->xendev.dom,
> > > +                                          c->page_gref,
> > > +                                          PROT_READ | PROT_WRITE);
> > > +    } else {
> > > +        assert(mfn == (xen_pfn_t)mfn);
> > > +
> > > +        c->page = xc_map_foreign_range(xen_xc, c->xendev.dom,
> > > +                                       XC_PAGE_SIZE,
> > > +                                       PROT_READ | PROT_WRITE, mfn);
> > > +    }
> > 
> > This is an extension of the protocol. It should be documented somewhere.
> > At least in the commit message and somewhere under docs/misc or
> > xen/include/public/io/fbif.h.
> > 
> 
> V2 will contain a better commit message, and I'll add a patch to the headers
> to document the changes.
> The same protocol extension docs should be in xen/include/public/io/fbif.h 
> and xen/include/public/io/kdbif.h, as this change covers the vfb and vkbd, or 
> would it be better to change the patch to only affect the vkbd?

I am OK with changing both vfb and vkbd but in that case you need to
document both.


> > 
> > >      if (c->page == NULL)
> > >   return -1;
> > >
> > >      xen_be_bind_evtchn(&c->xendev);
> > > -    xen_be_printf(&c->xendev, 1, "ring mfn %"PRIx64", remote-port %d,
> > local-port %d\n",
> > > -           mfn, c->xendev.remote_port, c->xendev.local_port);
> > > +
> > > +    if (c->page_gref) {
> > > +        xen_be_printf(&c->xendev, 1, "ring gref %d, remote-port %d, 
> > > local-
> > port %d\n",
> > > +                      c->page_gref, c->xendev.remote_port, 
> > > c->xendev.local_port);
> > > +    } else {
> > > +        xen_be_printf(&c->xendev, 1, "ring mfn %"PRIx64", remote-port %d,
> > local-port %d\n",
> > > +                      mfn, c->xendev.remote_port, c->xendev.local_port);
> > > +    }
> > >
> > >      return 0;
> > >  }
> > > @@ -120,8 +135,13 @@ static void common_unbind(struct common *c)  {
> > >      xen_be_unbind_evtchn(&c->xendev);
> > >      if (c->page) {
> > > - munmap(c->page, XC_PAGE_SIZE);
> > > +        if (c->page_gref) {
> > > +            xc_gnttab_munmap(c->xendev.gnttabdev, c->page, 1);
> > > +        } else {
> > > +            munmap(c->page, XC_PAGE_SIZE);
> > > +        }
> > >   c->page = NULL;
> > > +        c->page_gref = 0;
> > >      }
> > >  }
> > >
> > > @@ -954,6 +974,7 @@ static void fb_event(struct XenDevice *xendev)
> > >
> > >  struct XenDevOps xen_kbdmouse_ops = {
> > >      .size       = sizeof(struct XenInput),
> > > +    .flags      = DEVOPS_FLAG_NEED_GNTDEV,
> > >      .init       = input_init,
> > >      .initialise = input_initialise,
> > >      .connected  = input_connected,
> > > --
> > > 2.1.0
> > >
>