The following commit has been merged in the linux branch: commit 0f334a3e8c3586f81286345eb077ed32b375e8d6 Author: Kevin Cernekee cernekee@gmail.com Date: Mon Sep 7 11:11:31 2009 -0700

MIPS: Fix machine check exception in kmap_coherent()

On an SMP system with cache aliases, the following sequence of events may happen:

1) copy_user_highpage() runs on CPU0, invoking kmap_coherent() to create a temporary mapping in the fixmap region 2) copy_page() starts on CPU0 3) CPU1 sends CPU0 an IPI asking CPU0 to run local_r4k_flush_cache_page() 4) CPU0 takes the interrupt, interrupting copy_page() 5) local_r4k_flush_cache_page() on CPU0 calls kmap_coherent() again 6) The second invocation of kmap_coherent() on CPU0 tries to use the same fixmap virtual address that was being used by copy_user_highpage() 7) CPU0 throws a machine check exception for the TLB address conflict

Fixed by creating an extra set of fixmap entries for use in interrupt handlers. This prevents fixmap VA conflicts between copy_user_highpage() running in user context, and local_r4k_flush_cache_page() invoked from an SMP IPI.

Signed-off-by: Kevin Cernekee cernekee@gmail.com Signed-off-by: Ralf Baechle ralf@linux-mips.org

diff --git a/arch/mips/include/asm/fixmap.h b/arch/mips/include/asm/fixmap.h index efeddc8..0b89b83 100644 --- a/arch/mips/include/asm/fixmap.h +++ b/arch/mips/include/asm/fixmap.h @@ -48,9 +48,9 @@ enum fixed_addresses { #define FIX_N_COLOURS 8 FIX_CMAP_BEGIN, #ifdef CONFIG_MIPS_MT_SMTC - FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS), + FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS * 2), #else - FIX_CMAP_END = FIX_CMAP_BEGIN + FIX_N_COLOURS, + FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * 2), #endif #ifdef CONFIG_HIGHMEM /* reserved pte's for temporary kernel mappings */ diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c index 15aa190..8d1f4f3 100644 --- a/arch/mips/mm/init.c +++ b/arch/mips/mm/init.c @@ -27,6 +27,7 @@ #include <linux/swap.h> #include <linux/proc_fs.h> #include <linux/pfn.h> +#include <linux/hardirq.h>

#include <asm/asm-offsets.h> #include <asm/bootinfo.h> @@ -132,7 +133,10 @@ void *kmap_coherent(struct page *page, unsigned long addr) inc_preempt_count(); idx = (addr >> PAGE_SHIFT) & (FIX_N_COLOURS - 1); #ifdef CONFIG_MIPS_MT_SMTC - idx += FIX_N_COLOURS * smp_processor_id(); + idx += FIX_N_COLOURS * smp_processor_id() + + (in_interrupt() ? (FIX_N_COLOURS * NR_CPUS) : 0); +#else + idx += in_interrupt() ? FIX_N_COLOURS : 0; #endif vaddr = __fix_to_virt(FIX_CMAP_END - idx); pte = mk_pte(page, PAGE_KERNEL);