powerpc/mm/mce: Keep irqs disabled during lockless page table walk
__find_linux_mm_pte() returns a page table entry pointer after walking
the page table without holding locks. To make it safe against a THP
split and/or collapse, we disable interrupts around the lockless page
table walk. However we need to keep interrupts disabled as long as we
use the page table entry pointer that is returned.
Fix addr_to_pfn() to do that.
Fixes: ba41e1e1ccb9 ("powerpc/mce: Hookup derror (load/store) UE errors")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
[mpe: Rearrange code slightly and tweak change log wording]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190918145328.28602-1-aneesh.kumar@linux.ibm.com
diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
index 356e7b9..1cbf7f1 100644
--- a/arch/powerpc/kernel/mce_power.c
+++ b/arch/powerpc/kernel/mce_power.c
@@ -29,7 +29,7 @@
{
pte_t *ptep;
unsigned int shift;
- unsigned long flags;
+ unsigned long pfn, flags;
struct mm_struct *mm;
if (user_mode(regs))
@@ -39,18 +39,22 @@
local_irq_save(flags);
ptep = __find_linux_pte(mm->pgd, addr, NULL, &shift);
- local_irq_restore(flags);
- if (!ptep || pte_special(*ptep))
- return ULONG_MAX;
-
- if (shift > PAGE_SHIFT) {
- unsigned long rpnmask = (1ul << shift) - PAGE_SIZE;
-
- return pte_pfn(__pte(pte_val(*ptep) | (addr & rpnmask)));
+ if (!ptep || pte_special(*ptep)) {
+ pfn = ULONG_MAX;
+ goto out;
}
- return pte_pfn(*ptep);
+ if (shift <= PAGE_SHIFT)
+ pfn = pte_pfn(*ptep);
+ else {
+ unsigned long rpnmask = (1ul << shift) - PAGE_SIZE;
+ pfn = pte_pfn(__pte(pte_val(*ptep) | (addr & rpnmask)));
+ }
+
+out:
+ local_irq_restore(flags);
+ return pfn;
}
/* flush SLBs and reload */
