Date:	Mon, 14 Mar 2016 09:41:24 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	jonas@...thpole.se, Philip Li <philip.li@...el.com>,
	linux@...ts.openrisc.net, kbuild-all@...org,
	linux-kernel@...r.kernel.org, Tony Breeds <tony@...eyournoodle.com>
Subject: Re: [kbuild-all] drivers/vhost/vhost.c:718:3: error: call to
 '__compiletime_assert_718' declared with attribute error: BUILD_BUG_ON
 failed: __alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE

Hi Michael,

Sorry for the delay! I blacklisted it just now.

Fengguang

On Sun, Mar 13, 2016 at 04:57:26PM +0200, Michael S. Tsirkin wrote:
> On Thu, Mar 10, 2016 at 08:49:24AM +0800, Fengguang Wu wrote:
> > Hi Michael,
> > 
> > On Sun, Mar 06, 2016 at 10:37:07AM +0200, Michael S. Tsirkin wrote:
> > > I keep seeing these errors. Any openrisc/gcc/kbuild people
> > > interested in looking into this?
> >  
> > Sorry, currently the buildbot is running old gcc 4.5.1 cross compiler
> > for openrisc:
> > 
> > https://www.kernel.org/pub/tools/crosstool/files/bin/x86_64/4.5.1/x86_64-gcc-4.5.1-nolibc_or32-linux.tar.xz
> > 
> > I'll blacklist this error for now, until we upgraded to a new gcc
> > version that has this issue fixed.
> > 
> > Thanks,
> > Fengguang
> 
> Keep getting these errors, blacklisting did not seem to work.
> 
> > > On Sun, Feb 28, 2016 at 07:15:14AM +0800, kbuild test robot wrote:
> > > > Hi Michael,
> > > > 
> > > > FYI, the error/warning still remains.
> > > > 
> > > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > > head:   691429e13dfaf5b0994b07cc166db41bd608ee3d
> > > > commit: 5d9a07b0de512b77bf28d2401e5fe3351f00a240 vhost: relax used address alignment
> > > > date:   1 year, 2 months ago
> > > > config: openrisc-allmodconfig (attached as .config)
> > > > reproduce:
> > > >         wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
> > > >         chmod +x ~/bin/make.cross
> > > >         git checkout 5d9a07b0de512b77bf28d2401e5fe3351f00a240
> > > >         # save the attached .config to linux build tree
> > > >         make.cross ARCH=openrisc 
> > > > 
> > > > All errors (new ones prefixed by >>):
> > > > 
> > > >    drivers/vhost/vhost.c: In function 'vhost_vring_ioctl':
> > > > >> drivers/vhost/vhost.c:718:3: error: call to '__compiletime_assert_718' declared with attribute error: BUILD_BUG_ON failed: __alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE
> > > > 
> > > > vim +/__compiletime_assert_718 +718 drivers/vhost/vhost.c
> > > > 
> > > >    712			    (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
> > > >    713				r = -EFAULT;
> > > >    714				break;
> > > >    715			}
> > > >    716	
> > > >    717			/* Make sure it's safe to cast pointers to vring types. */
> > > >  > 718			BUILD_BUG_ON(__alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE);
> > > >    719			BUILD_BUG_ON(__alignof__ *vq->used > VRING_USED_ALIGN_SIZE);
> > > >    720			if ((a.avail_user_addr & (VRING_AVAIL_ALIGN_SIZE - 1)) ||
> > > >    721			    (a.used_user_addr & (VRING_USED_ALIGN_SIZE - 1)) ||
> > > > 
> > > > ---
> > > > 0-DAY kernel test infrastructure                Open Source Technology Center
> > > > https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
> > > 
> > > I still think it's a bug in the openrisc compiler used.
> > > 
> > > struct vring_avail {
> > >         unsigned short flags;
> > >         unsigned short idx;
> > > };
> > > 
> > > struct vring_avail *x;
> > > 
> > > int main(int argc, char **argv)
> > > {
> > > 
> > >         footest();
> > >         if (__alignof__(*x) == 1)
> > >                 foo1();
> > >         else if (__alignof__(*x) == 2)
> > >                 foo2();
> > >         else if (__alignof__(*x) == 4)
> > >                 foo4();
> > >         else if (__alignof__(*x) == 8)
> > >                 foo8();
> > >         else
> > >                 fooother();
> > >         return 0;
> > > }
> > > 
> > > when compiled with the openrisc compiler from kernel.org this calls foo4
> > > and it really should call foo2, since the openrisc manual says:
> > > 
> > > 16.1.2
> > > Aggregates and Unions
> > > Aggregates (structures and arrays) and unions assume the alignment of
> > > their most
> > > strictly aligned element.
> > > 
> > > and alignment for unsigned short is 2.
> > > 
> > > 
> > > 
> > > -- 
> > > MST
> > > _______________________________________________
> > > kbuild-all mailing list
> > > kbuild-all@...ts.01.org
> > > https://lists.01.org/mailman/listinfo/kbuild-all

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