Re: [Xen-devel] [PATCH] drm/xen-front: fix pointer casts

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

On 05/23/2018 12:19 PM, Juergen Gross wrote:
> On 21/05/18 09:39, Oleksandr Andrushchenko wrote:
> > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> >
> > Building for a 32-bit target results in warnings from casting
> > between a 32-bit pointer and a 64-bit integer. Fix the warnings
> > by casting those pointers to uintptr_t first.
> >
> > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > ---
> >   drivers/gpu/drm/xen/xen_drm_front.h       | 4 ++--
> >   drivers/gpu/drm/xen/xen_drm_front_shbuf.c | 2 +-
> >   2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/xen/xen_drm_front.h 
> > b/drivers/gpu/drm/xen/xen_drm_front.h
> > index 2c2479b571ae..8e15dbebc4ba 100644
> > --- a/drivers/gpu/drm/xen/xen_drm_front.h
> > +++ b/drivers/gpu/drm/xen/xen_drm_front.h
> > @@ -126,12 +126,12 @@ struct xen_drm_front_drm_info {
> >   
> >   static inline u64 xen_drm_front_fb_to_cookie(struct drm_framebuffer *fb)
> >   {
> > -       return (u64)fb;
> > +       return (u64)(uintptr_t)fb;
> Do you really still need the cast to u64?
Indeed, I can remove (u64) now, thank you
> >   }
> >   
> >   static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
> >   {
> > -       return (u64)gem_obj;
> > +       return (u64)(uintptr_t)gem_obj;
> >   }
> >   
> >   int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
> > diff --git a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c 
> > b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
> > index 8099cb343ae3..47fc93847765 100644
> > --- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
> > +++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
> > @@ -122,7 +122,7 @@ static void guest_calc_num_grefs(struct xen_drm_front_shbuf 
> > *buf)
> >   }
> >   
> >   #define xen_page_to_vaddr(page) \
> > -               ((phys_addr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
> > +               ((phys_addr_t)(uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
> phys_addr_t for a virtual address?
This is because the resulting value is then passed to gnttab_set_map_op/
gnttab_set_unmap_op which expects host address to be passed as
phys_addr_t addr :(
Please see [1], [2]: regardless of the fact that xen_page_to_vaddr does
produce host address I have to convert it to phys_addr_t then to pass to 
[1] and [2].
Please also see [3], [4], [5] which either cast to phys_addr_t or
unsigned long or u64.
> Juergen
[1] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/include/xen/grant_table.h#L147
[2] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/include/xen/grant_table.h#L163
[3] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/drivers/block/xen-blkback/blkback.c#L845
[4] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/drivers/net/xen-netback/netback.c#L334
[5] 
https://elixir.bootlin.com/linux/v4.17-rc6/source/drivers/xen/xenbus/xenbus_client.c#L478
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