From: Arnd Bergmann <arnd@arndb.de>
To: qemu-devel@nongnu.org
Cc: Jes Sorensen <Jes.Sorensen@redhat.com>,
Alex Williamson <alex.williamson@redhat.com>,
kvm@vger.kernel.org
Subject: Re: [Qemu-devel] Re: [PATCH] pc: e820 qemu_cfg tables need to be packed
Date: Thu, 14 Oct 2010 22:20:25 +0200 [thread overview]
Message-ID: <201010142220.26329.arnd@arndb.de> (raw)
In-Reply-To: <1287086288.2987.10.camel@x201>
On Thursday 14 October 2010 21:58:08 Alex Williamson wrote:
> If it works anywhere (I assume it works on 32bit), then it's only
> because it happened to get the alignment right. This just makes 64bit
> hosts get it right too. I don't see any compatibility issues,
> non-packed + 64bit = broken. Thanks,
I would actually assume that only x86-32 hosts got it right, because
all 32 bit hosts I've seen other than x86 also define 8 byte alignment
for uint64_t.
You might however consider making it
__attribute((__packed__, __aligned__(4)))
instead of just packed, because otherwise you make the alignment one byte,
which is not only different from what it used to be on x86-32 but also
will cause inefficient compiler outpout on platforms that don't have unaligned
word accesses in hardware.
Arnd
next prev parent reply other threads:[~2010-10-14 20:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-14 18:33 [Qemu-devel] [PATCH] pc: e820 qemu_cfg tables need to be packed Alex Williamson
2010-10-14 19:44 ` [Qemu-devel] " Jes Sorensen
2010-10-14 19:48 ` Anthony Liguori
2010-10-14 19:58 ` Alex Williamson
2010-10-14 19:59 ` Anthony Liguori
2010-10-14 20:20 ` Arnd Bergmann [this message]
2010-10-14 20:59 ` Alex Williamson
2010-10-14 21:19 ` Arnd Bergmann
2010-10-15 4:01 ` Alex Williamson
2010-10-15 4:08 ` [Qemu-devel] [PATCH v2] " Alex Williamson
2010-10-15 10:20 ` [Qemu-devel] " Arnd Bergmann
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