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Date: Thu, 21 Aug 2014 18:44:49 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] latest rc: virtio-blk hangs forever after migration
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To: Andrey Korolyov <andrey@xdel.ru>
Cc: Amit Shah <amit.shah@redhat.com>, Fam Zheng <famz@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, =?UTF-8?B?TWFyY2luIEdpYnXFgmE=?= <m.gibula@beyond.pl>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

Il 21/08/2014 18:41, Andrey Korolyov ha scritto:
> Sorry, the test series revealed that the problem is still here, but
> with lower hit ratio with modified 2.1-HEAD using selected argument
> set. The actual root of the issue is in '-cpu
> qemu64,hv_time,hv_relaxed,hv_vapic,hv_spinlocks=0x1000'
> Windows-specific addition which can be traded for some idle CPU
> consumption. Reproduction of bug is quite simple - fire up Windows VM,
> migrate it two-three times and then try to log in using rdesktop/VNC -
> if disk is frozen, login progress will freeze too. It is not so easy
> to detect blocked I/O on Windows in the interactive session due to
> lack of soft lockup warning equivalent, so one can try such a sequence
> to check.

What kernel version?

The ioapic patches at http://thread.gmane.org/gmane.linux.kernel/1671045
fixed exactly a Windows-specific hang in migration.  But it didn't require
Hyper-V enlightenments.

Paolo