When inserting SLB entries for EA above 512TB, we need to hard disable irq.
This will make sure we don't take a PMU interrupt that can possibly touch
user space address via a stack dump. To prevent this, we need to hard disable
the interrupt.
Also add a comment explaining why we don't need context synchronizing isync
with slbmte.
Fixes: f384796c4 ("powerpc/mm: Add support for handling > 512TB address in SLB
miss")
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
arch/powerpc/mm/slb.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index 66577cc66dc9..27f5b81c372a 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c
@@ -352,6 +352,14 @@ static void insert_slb_entry(unsigned long vsid, unsigned
long ea,
/*
* We are irq disabled, hence should be safe to access PACA.
*/
+ VM_WARN_ON(!irqs_disabled());
+
+ /*
+ * We can't take a PMU exception in the following code, so hard
+ * disable interrupts.
+ */
+ hard_irq_disable();
+
index = get_paca()->stab_rr;
/*
@@ -369,6 +377,11 @@ static void insert_slb_entry(unsigned long vsid, unsigned
long ea,
((unsigned long) ssize << SLB_VSID_SSIZE_SHIFT);
esid_data = mk_esid_data(ea, ssize, index);
+ /*
+ * No need for an isync before or after this slbmte. The exception
+ * we enter with and the rfid we exit with are context synchronizing.
+ * Also we only handle user segments here.
+ */
asm volatile("slbmte %0, %1" : : "r" (vsid_data), "r" (esid_data)
: "memory");
--
2.17.0
