Messages in this thread | | | Date | Sun, 28 Feb 2016 11:03:19 +0200 | From | "Michael S. Tsirkin" <> | 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 |
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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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