[PATCH] powerpc/eeh: Handle hugepages in ioremap space

Oliver O'Halloran oohall at gmail.com
Thu Jul 11 01:05:17 AEST 2019

In commit 4a7b06c157a2 ("powerpc/eeh: Handle hugepages in ioremap
space") support for using hugepages in the vmalloc and ioremap areas was
enabled for radix. Unfortunately this broke EEH MMIO error checking.

Detection works by inserting a hook which checks the results of the
ioreadXX() set of functions.  When a read returns a 0xFFs response we
need to check for an error which we do by mapping the (virtual) MMIO
address back to a physical address, then mapping physical address to a
PCI device via an interval tree.

When translating virt -> phys we currently assume the ioremap space is
only populated by PAGE_SIZE mappings. If a hugepage mapping is found we
emit a WARN_ON(), but otherwise handles the check as though a normal
page was found. In pathalogical cases such as copying a buffer
containing a lot of 0xFFs from BAR memory this can result in the system
not booting because it's too busy printing WARN_ON()s.

There's no real reason to assume huge pages can't be present and we're
prefectly capable of handling them, so do that.

Cc: Nicholas Piggin <npiggin at gmail.com>
Fixes: 4a7b06c157a2 ("powerpc/eeh: Handle hugepages in ioremap space")
Reported-by: Sachin Sant <sachinp at linux.vnet.ibm.com>
Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
I'm assuming that we aren't going to be doing THP in the ioremap area.
 arch/powerpc/kernel/eeh.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
index 4557fb1aeb2c..976ca0496442 100644
--- a/arch/powerpc/kernel/eeh.c
+++ b/arch/powerpc/kernel/eeh.c
@@ -354,10 +354,19 @@ static inline unsigned long eeh_token_to_phys(unsigned long token)
 	ptep = find_init_mm_pte(token, &hugepage_shift);
 	if (!ptep)
 		return token;
-	WARN_ON(hugepage_shift);
-	pa = pte_pfn(*ptep) << PAGE_SHIFT;
-	return pa | (token & (PAGE_SIZE-1));
+	pa = pte_pfn(*ptep);
+	/* On radix we can do hugepage mappings for io, so handle that */
+	if (hugepage_shift) {
+		pa <<= hugepage_shift;
+		pa |= token & ((1ul << hugepage_shift) - 1);
+	} else {
+		pa <<= PAGE_SHIFT;
+		pa |= token & (PAGE_SIZE - 1);
+	}
+	return pa;

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