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powerpc/mm/hash: hard disable irq in the SLB insert path 

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.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Aneesh Kumar K.V 2018-06-01 13:54:02 +05:30 committed by Michael Ellerman
parent ed515b6898
commit a5db5060e0
1 changed files with 13 additions and 0 deletions
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13
arch/powerpc/mm/slb.c
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@ -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");