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authorJames Bottomley <James.Bottomley@HansenPartnership.com>2011-04-15 12:37:22 -0500
committerJames Bottomley <James.Bottomley@suse.de>2011-04-15 12:55:56 -0500
commitb7d45818444a31948cfc7849136013a0ea54b2fb (patch)
treec24455fe3f41bffabb377fa9c855eaa7cac26a1e /arch/parisc/kernel/cache.c
parentd7dd2ff11b7fcd425aca5a875983c862d19a67ae (diff)
[PARISC] prevent speculative re-read on cache flush
According to Appendix F, the TLB is the primary arbiter of speculation. Thus, if a page has a TLB entry, it may be speculatively read into the cache. On linux, this can cause us incoherencies because if we're about to do a disk read, we call get_user_pages() to do the flush/invalidate in user space, but we still potentially have the user TLB entries, and the cache could speculate the lines back into userspace (thus causing stale data to be used). This is fixed by purging the TLB entries before we flush through the tmpalias space. Now, the only way the line could be re-speculated is if the user actually tries to touch it (which is not allowed). Signed-off-by: James Bottomley <James.Bottomley@suse.de>
Diffstat (limited to 'arch/parisc/kernel/cache.c')
-rw-r--r--arch/parisc/kernel/cache.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 3f11331c2775..83335f3da5fc 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -304,10 +304,20 @@ void flush_dcache_page(struct page *page)
offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
addr = mpnt->vm_start + offset;
+ /* The TLB is the engine of coherence on parisc: The
+ * CPU is entitled to speculate any page with a TLB
+ * mapping, so here we kill the mapping then flush the
+ * page along a special flush only alias mapping.
+ * This guarantees that the page is no-longer in the
+ * cache for any process and nor may it be
+ * speculatively read in (until the user or kernel
+ * specifically accesses it, of course) */
+
+ flush_tlb_page(mpnt, addr);
if (old_addr == 0 || (old_addr & (SHMLBA - 1)) != (addr & (SHMLBA - 1))) {
__flush_cache_page(mpnt, addr, page_to_phys(page));
if (old_addr)
- printk(KERN_ERR "INEQUIVALENT ALIASES 0x%lx and 0x%lx in file %s\n", old_addr, addr, mpnt->vm_file ? mpnt->vm_file->f_path.dentry->d_name.name : "(null)");
+ printk(KERN_ERR "INEQUIVALENT ALIASES 0x%lx and 0x%lx in file %s\n", old_addr, addr, mpnt->vm_file ? (char *)mpnt->vm_file->f_path.dentry->d_name.name : "(null)");
old_addr = addr;
}
}
@@ -499,6 +509,7 @@ flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr, unsigned long
{
BUG_ON(!vma->vm_mm->context);
+ flush_tlb_page(vma, vmaddr);
__flush_cache_page(vma, vmaddr, page_to_phys(pfn_to_page(pfn)));
}