parisc: Optimize flush_kernel_vmap_range and invalidate_kernel_vmap_range

The previously submitted patch did not resolve the random segmentation
faults observed on the phantom buildd system.  There are still
unresolved problems with the Debian 4.8 and 4.9 kernels on C8000.

The attached patch removes the flush of the offset map pages and does a
whole data cache flush for large ranges.  No other arch flushes the
offset map in these routines as far as I can tell.

I have not observed any random segmentation faults on rp3440 in two
weeks of testing with 4.10.0 and 4.10.1.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org      # v4.8+
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 22 insertions, 0 deletions

diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 0dc72d5de861..c32a09095216 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -616,3 +616,25 @@ flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr, unsigned long
                 __flush_cache_page(vma, vmaddr, PFN_PHYS(pfn));
         }
 }
+
+void flush_kernel_vmap_range(void *vaddr, int size)
+{
+        unsigned long start = (unsigned long)vaddr;
+
+        if ((unsigned long)size > parisc_cache_flush_threshold)
+                flush_data_cache();
+        else
+                flush_kernel_dcache_range_asm(start, start + size);
+}
+EXPORT_SYMBOL(flush_kernel_vmap_range);
+
+void invalidate_kernel_vmap_range(void *vaddr, int size)
+{
+        unsigned long start = (unsigned long)vaddr;
+
+        if ((unsigned long)size > parisc_cache_flush_threshold)
+                flush_data_cache();
+        else
+                flush_kernel_dcache_range_asm(start, start + size);
+}
+EXPORT_SYMBOL(invalidate_kernel_vmap_range);