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Re: [Qemu-devel] [PATCH] Support running QEMU on Valgrind


From: Stefan Weil
Subject: Re: [Qemu-devel] [PATCH] Support running QEMU on Valgrind
Date: Mon, 31 Oct 2011 18:09:01 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.23) Gecko/20110921 Thunderbird/3.1.15

Am 31.10.2011 07:38, schrieb Markus Armbruster:
Alexander Graf <address@hidden> writes:
On 30.10.2011, at 13:07, Stefan Weil wrote:
Valgrind is a tool which can automatically detect many kinds of bugs.

Running QEMU on Valgrind with x86_64 hosts was not possible because
Valgrind aborts when memalign is called with an alignment larger than
1 MiB. QEMU normally uses 2 MiB on Linux x86_64.

Now the alignment is reduced to the page size when QEMU is running on
Valgrind.

valgrind.h is a copy from Valgrind svn trunk r12226 with trailing
whitespace stripped but otherwise unmodified, so it still raises lots
of errors when checked with scripts/checkpatch.pl.

Can't we just require valgrind header files to be around when kvm is enabled? I would rather not copy code from other projects. Alternatively you could take the header and shrink it down to maybe 5 lines of inline asm code that would be a lot more readable :). You're #ifdef'ing on x86_64 already anyways.


It is included here to avoid a dependency on Valgrind.
Our usual way to avoid a hard dependency on something we want is to
detect it in configure, then do something like

#ifdef CONFIG_VALGRIND
#include "valgrind.h"
#else
#define RUNNING_ON_VALGRIND 0
#endif

[...]

Markus, you obviously did not read my last mail.
I know how configure works, so there is no need to teach me.

I wrote that I decided against the configure solution because
it is not adequate here. Adding a copy of valgrind.h which
is explicitly made for being copied is simpler and better:

* It avoids code in configure. There are already so many
  checks in configure that it takes a rather long time to run,
  and additional checks don't improve maintainability.

* It adds Valgrind support for any x86_64 QEMU binary
  without enforcing a build dependency on Valgrind.
  This is useful for QEMU packages in distributions.

You said that copies are evil without explaining why you
think so. What about the other copies in QEMU? There are
lots of them, and some (e.g. the Linux headers) were added
recently.

Cheers,
Stefan Weil




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