Re: [Xen-devel] [PATCH v5 0/8] xen: dma-buf support for grant device

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

On 07/23/2018 11:38 AM, Oleksandr Andrushchenko wrote:
> On 07/20/2018 05:08 PM, Boris Ostrovsky wrote:
> > On 07/20/2018 05:01 AM, Oleksandr Andrushchenko wrote:
> > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > >
> > > This work is in response to my previous attempt to introduce Xen/DRM
> > > zero-copy driver [1] to enable Linux dma-buf API [2] for Xen based
> > > frontends/backends. There is also an existing hyper_dmabuf approach
> > > available [3] which, if reworked to utilize the proposed solution,
> > > can greatly benefit as well.
> > Lot of warnings on  i386 build:
> >
> > In file included from
> > /data/upstream/linux-xen/drivers/gpu/drm/xen/xen_drm_front.c:24:
> > /data/upstream/linux-xen/drivers/gpu/drm/xen/xen_drm_front.h: In
> > function ‘xen_drm_front_fb_to_cookie’:
> > /data/upstream/linux-xen/drivers/gpu/drm/xen/xen_drm_front.h:129:9:
> > warning: cast from pointer to integer of different size
> > [-Wpointer-to-int-cast]
> >    return (u64)fb;
> >           ^
> > /data/upstream/linux-xen/drivers/gpu/drm/xen/xen_drm_front.h: In
> > function ‘xen_drm_front_dbuf_to_cookie’:
> > /data/upstream/linux-xen/drivers/gpu/drm/xen/xen_drm_front.h:134:9:
> > warning: cast from pointer to integer of different size
> > [-Wpointer-to-int-cast]
> >    return (u64)gem_obj;
> >           ^
> >    CC [M]  net/netfilter/ipset/ip_set_hash_ipport.o
> >    CC      drivers/media/rc/keymaps/rc-tango.o
> >    CC [M]  drivers/gpu/drm/vmwgfx/vmwgfx_fifo.o
> >    AR      drivers/misc/built-in.a
> > In file included from
> > /data/upstream/linux-xen/drivers/gpu/drm/xen/xen_drm_front_kms.c:20:
> > /data/upstream/linux-xen/drivers/gpu/drm/xen/xen_drm_front.h: In
> > function ‘xen_drm_front_fb_to_cookie’:
> >    CC [M]  drivers/gpu/drm/xen/xen_drm_front_conn.o
> > /data/upstream/linux-xen/drivers/gpu/drm/xen/xen_drm_front.h:129:9:
> > warning: cast from pointer to integer of different size
> > [-Wpointer-to-int-cast]
> >    return (u64)fb;
> > (and more)
> The above warnings already have a fix [1] which is expected in 4.19
> > and then
> >
> > data/upstream/linux-xen/drivers/xen/gntdev-dmabuf.c: In function
> > ‘gntdev_ioctl_dmabuf_exp_from_refs’:
> > /data/upstream/linux-xen/drivers/xen/gntdev-dmabuf.c:503:6: warning:
> > ‘args.fd’ may be used uninitialized in this function 
> > [-Wmaybe-uninitialized]
> >    *fd = args.fd;
> >    ~~~~^~~~~~~~~
> > /data/upstream/linux-xen/drivers/xen/gntdev-dmabuf.c:467:35: note:
> > ‘args.fd’ was declared here
> >    struct gntdev_dmabuf_export_args args;
> >                                     ^~~~
> Strangely, but my i386 build goes smooth.
> Which version of gcc you use and could you please give me your
> .config, so I can test the same?
Now I see this warning which seems to be a false positive.
Boris, could you please apply the following:

diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c
index e4c9f1f74476..0680dbcba616 100644
--- a/drivers/xen/gntdev-dmabuf.c
+++ b/drivers/xen/gntdev-dmabuf.c
@@ -495,6 +495,7 @@ static int dmabuf_exp_from_refs(struct gntdev_priv 
*priv, int flags,
        args.dmabuf_priv = priv->dmabuf_priv;
        args.count = map->count;
        args.pages = map->pages;
+       args.fd = -1;

        ret = dmabuf_exp_from_pages(&args);
        if (ret < 0)

or please let me know if you want me to resend with this fix?
> > -boris
> Thank you,
> Oleksandr
>
> [1] 
> https://cgit.freedesktop.org/drm/drm-misc/commit/?id=9eece5d9c6e0316f17091e37ff3ec87331bdedf3
Thank you,
Oleksandr

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