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Re: [Qemu-ppc] [Qemu-devel] [RFC PATCH] powerpc: add PVR mask support

From: Anthony Liguori
Subject: Re: [Qemu-ppc] [Qemu-devel] [RFC PATCH] powerpc: add PVR mask support
Date: Thu, 15 Aug 2013 11:04:43 -0500
User-agent: Notmuch/0.15.2+202~g0c4b8aa (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu)

Andreas Färber <address@hidden> writes:

> Am 15.08.2013 15:12, schrieb Anthony Liguori:
>> Everyone is talking past each other and no one is addressing the real
>> problem.  There are two distinct issues here:
>> 1) We have two ABIs that cannot be changed unless there's a very good
>>    reason to.  Alexey's original patch breaks both.  The guest ABI
>>    cannot change given a fixed command line.
>>    IOW, the exposed PVR value for -cpu POWER7 cannot change across
>>    versions of QEMU or when running on different hardware.  This breaks
>>    live migration and save/resume.
>>    We also cannot break the command line interface.  If the last version
>>    of QEMU supported -cpu POWER7_v2.1, then we must continue to support
>>    that.
> 1a) How should -cpu 0xDEADBEEF or -cpu DEADBEEF behave.
>     I expect it to error out as before

Correct although that can't be guaranteed.  Maybe there is a 'DEADBEEF'
cpu model in the future.  This is the architecture of the ripvanwinkle
and eieio instructions after all :-)

>     rather than applying the same fuzz/mask that -cpu host might.

Fuzzing CPU models sounds like an awful idea to me.


Anthony Liguori

>     That would let us implement our own fuzz logic in kvm.c,
>     operating on a GSList of ObjectClasses to handle multiple matches.
> Regards,
> Andreas

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