From: Richard Henderson <rth@twiddle.net>
To: Avi Kivity <avi@redhat.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>,
qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: Re: [Qemu-devel] [PATCH v2] memory: use signed arithmetic
Date: Wed, 03 Aug 2011 07:59:27 -0700 [thread overview]
Message-ID: <4E39624F.4020709@twiddle.net> (raw)
In-Reply-To: <1312361774-29086-1-git-send-email-avi@redhat.com>
On 08/03/2011 01:56 AM, Avi Kivity wrote:
> When trying to map an alias of a ram region, where the alias starts at
> address A and we map it into address B, and A > B, we had an arithmetic
> underflow. Because we use unsigned arithmetic, the underflow converted
> into a large number which failed addrrange_intersects() tests.
>
> The concrete example which triggered this was cirrus vga mapping
> the framebuffer at offsets 0xc0000-0xc7fff (relative to the start of
> the framebuffer) into offsets 0xa0000 (relative to system addres space
> start).
>
> With our favorite analogy of a windowing system, this is equivalent to
> dragging a subwindow off the left edge of the screen, and failing to clip
> it into its parent window which is on screen.
>
> Fix by switching to signed arithmetic.
>
> Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
r~
next prev parent reply other threads:[~2011-08-03 14:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-03 8:56 [Qemu-devel] [PATCH v2] memory: use signed arithmetic Avi Kivity
2011-08-03 14:59 ` Richard Henderson [this message]
2011-08-05 16:45 ` Anthony Liguori
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