powerpc/powernv: Call OPAL sync before kexec'ing

Its possible that OPAL may be writing to host memory during
kexec (like dump retrieve scenario). In this situation we might
end up corrupting host memory.

This patch makes OPAL sync call to make sure OPAL stops
writing to host memory before kexec'ing.

Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 19884b2a51b4..a932feb2901c 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -145,8 +145,10 @@ static void pnv_shutdown(void)
         /* Let the PCI code clear up IODA tables */
         pnv_pci_shutdown();
 
-        /* And unregister all OPAL interrupts so they don't fire
-         * up while we kexec
+        /*
+         * Stop OPAL activity: Unregister all OPAL interrupts so they
+         * don't fire up while we kexec and make sure all potentially
+         * DMA'ing ops are complete (such as dump retrieval).
          */
         opal_shutdown();
 }