On Monday, July 4, 2016 10:21:45 AM CEST Geert Uytterhoeven wrote: > On Mon, Jul 4, 2016 at 10:12 AM, Geert Uytterhoeven > <geert@xxxxxxxxxxxxxx> wrote: > > JFYI, when comparing v4.7-rc6[1] to v4.7-rc5[3], the summaries are: > > - build errors: +3/-2 > > + /home/kisskb/slave/src/drivers/vhost/vhost.c: error: call to > '__compiletime_assert_844' declared with attribute error: BUILD_BUG_ON > failed: __alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE: => 844:3 > > arm-randconfig > > > [1] http://kisskb.ellerman.id.au/kisskb/head/10562/ (260 out of 263 configs) > > [3] http://kisskb.ellerman.id.au/kisskb/head/10532/ (260 out of 263 configs) I don't see any changes in the code in this time frame, but this is the code causing it: struct vring_avail { __virtio16 flags; __virtio16 idx; __virtio16 ring[]; }; /* The virtqueue structure describes a queue attached to a device. */ struct vhost_virtqueue { struct vhost_dev *dev; /* The actual ring of buffers. */ struct mutex mutex; unsigned int num; struct vring_desc __user *desc; struct vring_avail __user *avail; struct vring_used __user *used; ... }; struct vhost_virtqueue *vq; BUILD_BUG_ON(__alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE); The alignment of the *vq->avail should be '2' on all architectures, however an ARM OABI compiler will have a padded structure with alignment '4'. Looking at the build logs, I find it only in a single randconfig build at http://kisskb.ellerman.id.au/kisskb/buildresult/12735927/ which apparently enabled the vhost driver in combination with ARM_AEABI=n. In my own randconfig builds I am forcing ARM_AEABI=y because there are a couple of other problems with OABI. If we want to avoid this one, we could make the inclusion of drivers/vhost/Kconfig from arch/arm/kvm/Kconfig depend on CONFIG_AEABI, or perhaps go further force-enable CONFIG_AEABI for ARMv6k and higher (cmpxchg64() is broken on OABI too), and only include vhost if KVM is enabled (KVM in turn requires ARMv7). Arnd -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
