From: "Thomas Hellström" <thellstrom@vmware.com>
To: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: 2.6.29 pat issue
Date: Thu, 05 Feb 2009 13:47:31 +0100 [thread overview]
Message-ID: <498ADFE3.9020907@vmware.com> (raw)
Hi!
The function in include/linux/mm.h:
is_linear_pfn_mapping()
doesn't seem valid to me.
In particular, we have VMAs to graphics devices in which vma->vm_pgoff
is non-zero (Points to an offset in the drm device node), and the VMA is
sparsely populated with pfns pointing to uncached discontigous RAM pages.
This causes the X86 PAT code to hit the optimized path when it
shouldn't, and issue a warning.
Also a question about the philosofy behind this strict checking that all
PTEs have the same caching attributes: I guess this is only to catch
bugs in kernel drivers that don't get this right. At the same time, now
that also user-space VMAs are checked this will probably have a
significant performance impact. Shouldn't this checking really live
behind a debug define?
Thanks,
Thomas
next reply other threads:[~2009-02-05 12:47 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-05 12:47 Thomas Hellström [this message]
2009-02-05 18:03 ` 2.6.29 pat issue Pallipadi, Venkatesh
2009-02-05 21:32 ` Thomas Hellstrom
2009-02-05 23:08 ` Pallipadi, Venkatesh
2009-02-06 9:51 ` Thomas Hellström
2009-02-06 1:11 ` Eric W. Biederman
2009-02-06 9:43 ` Thomas Hellström
2009-03-04 6:08 ` Pallipadi, Venkatesh
2009-03-04 9:56 ` Thomas Hellstrom
2009-03-06 22:38 ` Pallipadi, Venkatesh
2009-03-06 23:44 ` Thomas Hellstrom
2009-03-10 1:39 ` Pallipadi, Venkatesh
2009-03-10 8:22 ` Thomas Hellstrom
2009-03-10 17:42 ` Pallipadi, Venkatesh
2009-03-11 9:17 ` Thomas Hellstrom
2009-03-11 9:33 ` Ingo Molnar
2009-03-11 17:54 ` [PATCH] VM, x86, PAT: Change implementation of is_linear_pfn_mapping Pallipadi, Venkatesh
2009-03-11 22:09 ` Frans Pop
2009-03-12 0:31 ` Pallipadi, Venkatesh
2009-03-12 3:22 ` Pallipadi, Venkatesh
2009-03-12 5:45 ` Frans Pop
2009-03-12 18:59 ` Pallipadi, Venkatesh
2009-03-12 20:30 ` Frans Pop
2009-03-12 22:48 ` Pallipadi, Venkatesh
2009-03-13 0:36 ` Ingo Molnar
2009-03-13 0:45 ` [PATCH] VM, x86, PAT: Change is_linear_pfn_mapping to not use vm_pgoff Pallipadi, Venkatesh
2009-03-13 4:03 ` [tip:x86/urgent] " Pallipadi, Venkatesh
2009-03-13 16:25 ` Nick Piggin
2009-03-13 17:00 ` Pallipadi, Venkatesh
2009-03-14 2:52 ` Nick Piggin
2009-03-13 23:35 ` [PATCH] Add a new vm flag to track full pfnmap at mmap Pallipadi, Venkatesh
2009-03-14 2:53 ` Nick Piggin
2009-03-14 8:54 ` [tip:x86/urgent] VM, x86, PAT: add " Pallipadi, Venkatesh
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