From: Jan Niehusmann <jan-7BUxKyILgIXQT0dZR+AlfA@public.gmane.org>
To: Aaron Campbell <aaron-J6AcJDG0ZEwdnm+yROfE0A@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
Subject: Re: [PATCH] iommu/vt-d: Fix infinite loop in free_all_cpu_cached_iovas
Date: Sun, 3 Jul 2016 09:53:14 +0200 [thread overview]
Message-ID: <20160703075314.GA3128@x61s.reliablesolutions.de> (raw)
In-Reply-To: <1467505404-3561-1-git-send-email-aaron-J6AcJDG0ZEwdnm+yROfE0A@public.gmane.org>
On Sat, Jul 02, 2016 at 09:23:24PM -0300, Aaron Campbell wrote:
> Per VT-d spec Section 10.4.2 ("Capability Register"), the maximum
> number of possible domains is 64K; indeed this is the maximum value
> that the cap_ndoms() macro will expand to.
Good catch. Before 3bd4f9112f87, the loop ended at the fixed value
0xffff. I didn't notice that cap_ndoms() could not only be lower than
that, like on my notebook, but could also be greater. Therefore I didn't
even look at the type of 'did'.
So, strictly speaking, the original code would not only overflow for
small values of cap_ndoms, but would miss the entry at 0xffff in case
cap_ndoms was 0x10000. My patch unfortunately changed that to an endless
loop, instead.
Jan
next prev parent reply other threads:[~2016-07-03 7:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-03 0:23 [PATCH] iommu/vt-d: Fix infinite loop in free_all_cpu_cached_iovas Aaron Campbell
[not found] ` <1467505404-3561-1-git-send-email-aaron-J6AcJDG0ZEwdnm+yROfE0A@public.gmane.org>
2016-07-03 7:53 ` Jan Niehusmann [this message]
2016-07-04 11:37 ` Joerg Roedel
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