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

[Owen Smith <owen.smith@citrix.com>]

> -----Original Message-----
> From: Stefano Stabellini [mailto:stefano.stabellini@eu.citrix.com]
> Sent: 11 September 2014 02:01
> To: Owen Smith
> Cc: qemu-devel@nongnu.org; xen-devel@lists.xen.org; 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 <owen.smith@citrix.com>
> > ---
> >  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?


> 
> >      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
> >