From: "Richard W.M. Jones" <rjones@redhat.com>
To: Rob Landley <rob@landley.net>
Cc: "Thomas Huth" <thuth@redhat.com>,
qemu-devel@nongnu.org, "Marc Marí" <markmb@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>
Subject: Re: [Qemu-devel] Commit b2a575a1c652 broke i486 support.
Date: Wed, 31 May 2017 10:03:22 +0100 [thread overview]
Message-ID: <20170531090322.GD31999@redhat.com> (raw)
In-Reply-To: <7e4d7d67-3312-2d2a-ab64-8c0f171d9118@landley.net>
On Tue, May 30, 2017 at 02:05:15PM -0500, Rob Landley wrote:
> On 05/29/2017 05:14 AM, Richard W.M. Jones wrote:
> > I see in the disassembly use of cmovne (new in Pentium Pro) and
> > bswap (new in 486).
> > [http://cse.unl.edu/~goddard/Courses/CSCE351/IntelArchitecture/InstructionSetSummary.pdf]
> >
> > The cmovne instruction is generated by the compiler (GCC in my case),
> >
> > The following patch removes the cmovne instruction, so it should work
> > on 486 (although I didn't test it). It's not possible to remove bswap
> > without surgery on the inline assembler.
>
> Is there any way to make it just _not_ load the option rom for -cpu 486?
> It ran fine before that thing went in...
Well it ran, but it was very slow. The DMA method can be literally
orders of magnitude faster.
Does adding the flag I suggested help?
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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next prev parent reply other threads:[~2017-05-31 9:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-28 5:18 [Qemu-devel] Commit b2a575a1c652 broke i486 support Rob Landley
2017-05-29 9:22 ` Thomas Huth
2017-05-29 10:14 ` Richard W.M. Jones
2017-05-29 11:20 ` Thomas Huth
2017-05-30 19:05 ` Rob Landley
2017-05-31 8:58 ` Thomas Huth
2017-05-31 9:03 ` Richard W.M. Jones [this message]
2017-05-31 12:34 ` Paolo Bonzini
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