Skip to content

K
Kernel

openeuler / Kernel
1 年多 前同步成功

通知 8
Star 0
Fork 0
K
Kernel
切换分支/标签
  1. 20 6月, 2008 1 次提交
  3. 18 6月, 2008 3 次提交
    • P
      [POWERPC] Clear sub-page HPTE present bits when demoting page size · 65ba6cdc
      由 Paul Mackerras 提交于 
      When we demote a slice from 64k to 4k, and we are about to insert an
HPTE for a 4k subpage and we notice that there is an existing 64k
HPTE, we first invalidate that HPTE before inserting the new 4k
subpage HPTE.  Since the bits that encode which hash bucket the old
HPTE was in overlap with the bits that encode which of the 16 subpages
have HPTEs, we need to clear out the subpage HPTE-present bits before
starting to insert HPTEs for the 4k subpages.  If we don't do that, we
can erroneously think that a subpage already has an HPTE when it
doesn't.

That in itself wouldn't be such a problem except that when we go to
update the HPTE that we think is present on machines with a
hypervisor, the hypervisor can tell us that the HPTE we think is there
is actually there even though it isn't, which can lead to a process
getting stuck in a loop, continually faulting.  The reason for the
confusion is that the AVPN (abbreviated virtual page number) we are
looking for in the HPTE for a 4k subpage can actually match the AVPN
in a stale HPTE for another 64k page.  For example, the HPTE for
the 4k subpage at 0x84000f000 will be in the same hash bucket and have
the same AVPN as the HPTE for the 64k page at 0x8400f0000.

This fixes the code to clear out the subpage HPTE-present bits.
Signed-off-by: NPaul Mackerras <paulus@samba.org>
      65ba6cdc
    • J
      [POWERPC] 4xx: Clear new TLB cache attribute bits in Data Storage vector · b17879f7
      由 Josh Boyer 提交于 
      A recent commit added support for the new 440x6 and 464 cores that have the
added WL1, IL1I, IL1D, IL2I, and ILD2 bits for the caching attributes in the
TLBs.  The new bits were cleared in the finish_tlb_load function, however a
similar bit of code was missed in the DataStorage interrupt vector.
Signed-off-by: NJosh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>
      b17879f7
    • L
      x86-64: Fix "bytes left to copy" return value for copy_from_user() · 42a886af
      由 Linus Torvalds 提交于 
      Most users by far do not care about the exact return value (they only
really care about whether the copy succeeded in its entirety or not),
but a few special core routines actually care deeply about exactly how
many bytes were copied from user space.

And the unrolled versions of the x86-64 user copy routines would
sometimes report that it had copied more bytes than it actually had.

Very few uses actually have partial copies to begin with, but to make
this bug even harder to trigger, most x86 CPU's use the "rep string"
instructions for normal user copies, and that version didn't have this
issue.

To make it even harder to hit, the one user of this that really cared
about the return value (and used the uncached version of the copy that
doesn't use the "rep string" instructions) was the generic write
routine, which pre-populated its source, once more hiding the problem by
avoiding the exception case that triggers the bug.

In other words, very special thanks to Bron Gondwana who not only
triggered this, but created a test-program to show it, and bisected the
behavior down to commit 08291429 ("mm:
fix pagecache write deadlocks") which changed the access pattern just
enough that you can now trigger it with 'writev()' with multiple
iovec's.

That commit itself was not the cause of the bug, it just allowed all the
stars to align just right that you could trigger the problem.

[ Side note: this is just the minimal fix to make the copy routines
  (with __copy_from_user_inatomic_nocache as the particular version that
  was involved in showing this) have the right return values.

  We really should improve on the exceptional case further - to make the
  copy do a byte-accurate copy up to the exact page limit that causes it
  to fail.  As it is, the callers have to do extra work to handle the
  limit case gracefully. ]
Reported-by: NBron Gondwana <brong@fastmail.fm>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

 (which didn't have this problem), and since
most users that do the carethis was very hard to trigger, but
      42a886af
  5. 17 6月, 2008 2 次提交
  7. 16 6月, 2008 28 次提交
  9. 13 6月, 2008 6 次提交