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

  • To: Roman Shaposhnik <roman@xxxxxxxxxx>
  • From: Anthony PERARD <anthony.perard@xxxxxxxxxx>
  • Date: Thu, 1 Aug 2019 11:30:19 +0100
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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.

> 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.

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


Anthony PERARD

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