Re: [PATCH v2] drm/r128: fix build for UML

[Randy Dunlap]

On 10/10/21 12:49 PM, Sam Ravnborg wrote:
> Hi Randy,
>
> On Sun, Oct 10, 2021 at 10:29:55AM -0700, Randy Dunlap wrote:
> > Fix a build error on CONFIG_UML, which does not support (provide)
> > wbinvd(). UML can use the generic mb() instead.
> >
> > ../drivers/gpu/drm/r128/ati_pcigart.c: In function ‘drm_ati_pcigart_init’:
> > ../drivers/gpu/drm/r128/ati_pcigart.c:218:2: error: implicit declaration of function ‘wbinvd’ [-Werror=implicit-function-declaration]
> >    wbinvd();
> >    ^~~~~~
> >
> > Fixes: 68f5d3f3b654 ("um: add PCI over virtio emulation driver")
> > Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> > Cc: David Airlie <airlied@xxxxxxxx>
> > Cc: Daniel Vetter <daniel@xxxxxxxx>
> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: Jeff Dike <jdike@xxxxxxxxxxx>
> > Cc: Richard Weinberger <richard@xxxxxx>
> > Cc: Anton Ivanov <anton.ivanov@xxxxxxxxxxxxxxxxxx>
> > Cc: linux-um@xxxxxxxxxxxxxxxxxxx
> > ---
> > v2: update Fixes: tag (thanks, Johannes)
> >
> >   drivers/gpu/drm/r128/ati_pcigart.c |    2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > --- linux-next-20211007.orig/drivers/gpu/drm/r128/ati_pcigart.c
> > +++ linux-next-20211007/drivers/gpu/drm/r128/ati_pcigart.c
> > @@ -215,7 +215,7 @@ int drm_ati_pcigart_init(struct drm_devi
> >   	}
> >   	ret = 0;
> >   
> > -#if defined(__i386__) || defined(__x86_64__)
> > +#if (defined(__i386__) || defined(__x86_64__)) && !defined(CONFIG_UML)
> >   	wbinvd();
> >   #else
> >   	mb();
>
> If we look at drivers/video/fbdev/i810/i810_main.h
> then it looks like we can replace the above with a simple:
> #ifdef CONFIG_X86
> 	wbinvd();
> #else
> 	mb();
> #endif
>
> If you think this would work could you try it out.
> It would be nicer with the simpler variant.

Hi Sam,
Good idea, thanks.

OK, I tested it, it works fine.

Will resend the patch later...

> Note: I have no clue what wbinvd() does - seems like some x86 assembler
> specific thingy.


--
~Randy