The following commit has been merged in the linux branch: commit 8d8997f34e66124577db52f6e7ee10ab5f869e07 Author: Benjamin Herrenschmidt benh@kernel.crashing.org Date: Mon Oct 12 20:43:47 2009 +0000

powerpc/mm: Fix hang accessing top of vmalloc space

On pSeries, we always force the IO space to be mapped using 4K pages even with a 64K base page size to cope with some limitations in the HV interface to some devices.

However, the SLB miss handler code to discriminate between vmalloc and ioremap space uses a CPU feature section such that the code is nop'ed out when the processor support large pages non-cachable mappings.

Thus, we end up always using the ioremap page size for vmalloc segments on such processors, causing a discrepency between the segment and the hash table, and thus a hang continously hashing the page.

It works for the first segment of the vmalloc space since that segment is "bolted" in by C code correctly, and thankfully we almost never use the vmalloc space beyond the first segment, but the new percpu code made the bug happen.

This fixes it by removing the feature section from the assembly, we now always do the comparison between vmalloc and ioremap.

Signed-off-by; Benjamin Herrenschmidt benh@kernel.crashing.org

Signed-off-by: Benjamin Herrenschmidt benh@kernel.crashing.org

diff --git a/arch/powerpc/mm/slb_low.S b/arch/powerpc/mm/slb_low.S index bc44dc4..95ce355 100644 --- a/arch/powerpc/mm/slb_low.S +++ b/arch/powerpc/mm/slb_low.S @@ -72,19 +72,17 @@ _GLOBAL(slb_miss_kernel_load_vmemmap) 1: #endif /* CONFIG_SPARSEMEM_VMEMMAP */

- /* vmalloc/ioremap mapping encoding bits, the "li" instructions below - * will be patched by the kernel at boot + /* vmalloc mapping gets the encoding from the PACA as the mapping + * can be demoted from 64K -> 4K dynamically on some machines */ -BEGIN_FTR_SECTION - /* check whether this is in vmalloc or ioremap space */ clrldi r11,r10,48 cmpldi r11,(VMALLOC_SIZE >> 28) - 1 bgt 5f lhz r11,PACAVMALLOCSLLP(r13) b 6f 5: -END_FTR_SECTION_IFCLR(CPU_FTR_CI_LARGE_PAGE) -_GLOBAL(slb_miss_kernel_load_io) + /* IO mapping */ + _GLOBAL(slb_miss_kernel_load_io) li r11,0 6: BEGIN_FTR_SECTION