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Re: [Xen-devel] [BUG] Assertion failed: !blk->legacy_dev

On Thu, Aug 1, 2019 at 3:30 AM Anthony PERARD <anthony.perard@xxxxxxxxxx> wrote:
> On Wed, Jul 31, 2019 at 01:11:22PM -0700, Roman Shaposhnik wrote:
> > Hi!
> Hi Roman,
> Thanks for the bug report!
> That bug (technical debt really) was fixed in QEMU 4.0 (so will be fixed
> in Xen 4.13). It's a series of patch with the last one been db9ff46 if
> you want to have a look.

Got it! Is there any quick way how I can check that this, indeed, solves
our problem and I can remove the out-of-tree patch? I just really
want to make sure that when 4.13 comes out -- the issue is fixed.

I'm still a little bit new to Xen development, so I guess I need to combine:
somehow to get the same tree I get when I download an official release?

Is there a script or better yet a nightly build of some sort?

> > Andrew reminded me that EVE has a weird in-tree patch for Xen's qemu
> > to deal with an issue we can't quite explain:
> >     
> > https://github.com/lf-edge/eve/blob/master/pkg/xen-tools/patches-4.12.0/01-remove-assert.patch
> >
> > The way this problem manifests itself is *sometime after* an HVM domain
> > with a qcow2 disk attached get started we get QEMU failing with:
> >     Assertion failed: !blk->legacy_dev
> > (/xen/tools/qemu-xen/block/block-backend.c: blk_get_attached_dev_id:
> > 903)
> I can tell you more about how to trigger the assertion failure. Simply
> running `xentop' will trigger the bug. That tool run the QMP command
> "query-block" which will trigger the bug, there are probably other QMP
> command or HMP or monitor command which would do the same if you use a
> different monitoring software.

That's exactly right! Exactly what I'm seeing right now.

> So you could run with a newer version of QEMU or keep the patch that
> removes the assert.

So... are you saying that the in-tree (Xen's fork of) qemu can be ditched and
we can simply run with upstream qemu 4.0?


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