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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2012-04-11 14:28:07 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-04-22 16:21:45 -0700
commita741ac8bc6f3940013cfd204a8457caa1fcc202f (patch)
tree550fb4924b7f3a5597b33013a26c64b8a83d2852 /Makefile
parent41c4aac58d6c754e0bf7936f25b9815a3ef66f85 (diff)
S390: fix tlb flushing for page table pages
commit cd94154cc6a28dd9dc271042c1a59c08d26da886 upstream. Git commit 36409f6353fc2d7b6516e631415f938eadd92ffa "use generic RCU page-table freeing code" introduced a tlb flushing bug. Partially revert the above git commit and go back to s390 specific page table flush code. For s390 the TLB can contain three types of entries, "normal" TLB page-table entries, TLB combined region-and-segment-table (CRST) entries and real-space entries. Linux does not use real-space entries which leaves normal TLB entries and CRST entries. The CRST entries are intermediate steps in the page-table translation called translation paths. For example a 4K page access in a three-level page table setup will create two CRST TLB entries and one page-table TLB entry. The advantage of that approach is that a page access next to the previous one can reuse the CRST entries and needs just a single read from memory to create the page-table TLB entry. The disadvantage is that the TLB flushing rules are more complicated, before any page-table may be freed the TLB needs to be flushed. In short: the generic RCU page-table freeing code is incorrect for the CRST entries, in particular the check for mm_users < 2 is troublesome. This is applicable to 3.0+ kernels. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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