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Message-ID: <20160306083707.GA29096@redhat.com>
Date: Sun, 6 Mar 2016 10:37:07 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: kbuild test robot <fengguang.wu@...el.com>
Cc: kbuild-all@...org, linux-kernel@...r.kernel.org,
linux@...ts.openrisc.net, jonas@...thpole.se,
Philip Li <philip.li@...el.com>
Subject: Re: 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
I keep seeing these errors. Any openrisc/gcc/kbuild people
interested in looking into this?
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
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