Revert "x86 PAT: remove CPA WARN_ON for zero pte"

This reverts commit 58dab916dfb57328d50deb0aa9b3fc92efa248ff, which
makes my Nehalem come to a nasty crawling almost-halt.  It looks like it
turns off caching of regular kernel RAM, with the understandable
slowdown of a few orders of magnitude as a result.

Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 4cf30dee816154fcda7229b6967a28d644bbb746..e89d24815f26760370a17616e7f0ed4e1d57cfd2 100644 (file)
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -555,12 +555,10 @@ repeat:
        if (!pte_val(old_pte)) {
                if (!primary)
                        return 0;
-
-               /*
-                *  Special error value returned, indicating that the mapping
-                * did not exist at this address.
-                */
-               return -EFAULT;
+               WARN(1, KERN_WARNING "CPA: called for zero pte. "
+                      "vaddr = %lx cpa->vaddr = %lx\n", address,
+                      *cpa->vaddr);
+               return -EINVAL;
        }
 
        if (level == PG_LEVEL_4K) {

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 160c42d3eb8f0a5393140b43ebb496cf8fe200d1..8b08fb955274148454a2acaa538c78215322e655 100644 (file)
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -505,35 +505,6 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 }
 #endif /* CONFIG_STRICT_DEVMEM */
 
-/*
- * Change the memory type for the physial address range in kernel identity
- * mapping space if that range is a part of identity map.
- */
-static int kernel_map_sync_memtype(u64 base, unsigned long size,
-                                       unsigned long flags)
-{
-       unsigned long id_sz;
-       int ret;
-
-       if (!pat_enabled || base >= __pa(high_memory))
-               return 0;
-
-       id_sz = (__pa(high_memory) < base + size) ?
-                                               __pa(high_memory) - base :
-                                               size;
-
-       ret = ioremap_change_attr((unsigned long)__va(base), id_sz, flags);
-       /*
-        * -EFAULT return means that the addr was not valid and did not have
-        * any identity mapping. That case is a success for
-        * kernel_map_sync_memtype.
-        */
-       if (ret == -EFAULT)
-               ret = 0;
-
-       return ret;
-}
-
 int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
                                unsigned long size, pgprot_t *vma_prot)
 {
@@ -584,7 +555,9 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
        if (retval < 0)
                return 0;
 
-       if (kernel_map_sync_memtype(offset, size, flags)) {
+       if (((pfn < max_low_pfn_mapped) ||
+            (pfn >= (1UL<<(32 - PAGE_SHIFT)) && pfn < max_pfn_mapped)) &&
+           ioremap_change_attr((unsigned long)__va(offset), size, flags) < 0) {
                free_memtype(offset, offset + size);
                printk(KERN_INFO
                "%s:%d /dev/mem ioremap_change_attr failed %s for %Lx-%Lx\n",
@@ -632,7 +605,7 @@ static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
                                int strict_prot)
 {
        int is_ram = 0;
-       int ret;
+       int id_sz, ret;
        unsigned long flags;
        unsigned long want_flags = (pgprot_val(*vma_prot) & _PAGE_CACHE_MASK);
 
@@ -673,7 +646,15 @@ static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
                                     flags);
        }
 
-       if (kernel_map_sync_memtype(paddr, size, flags)) {
+       /* Need to keep identity mapping in sync */
+       if (paddr >= __pa(high_memory))
+               return 0;
+
+       id_sz = (__pa(high_memory) < paddr + size) ?
+                               __pa(high_memory) - paddr :
+                               size;
+
+       if (ioremap_change_attr((unsigned long)__va(paddr), id_sz, flags) < 0) {
                free_memtype(paddr, paddr + size);
                printk(KERN_ERR
                        "%s:%d reserve_pfn_range ioremap_change_attr failed %s "