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SubjectRe: [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,

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

> 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@lists.01.org
> https://lists.01.org/mailman/listinfo/kbuild-all

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