Patch "powerpc/powernv: Increase memory block size to 1GB on radix" has been added to the 4.13-stable tree

Patch "powerpc/powernv: Increase memory block size to 1GB on radix" has been added to the 4.13-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    powerpc/powernv: Increase memory block size to 1GB on radix

to the 4.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     powerpc-powernv-increase-memory-block-size-to-1gb-on-radix.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 53ecde0b9126ff140abe3aefd7f0ec64d6fa36b0 Mon Sep 17 00:00:00 2001
From: Anton Blanchard <anton@samba.org>
Date: Thu, 7 Sep 2017 15:05:51 +1000
Subject: powerpc/powernv: Increase memory block size to 1GB on radix

From: Anton Blanchard <anton@samba.org>

commit 53ecde0b9126ff140abe3aefd7f0ec64d6fa36b0 upstream.

Memory hot unplug on PowerNV radix hosts is broken. Our memory block
size is 256MB but since we map the linear region with very large
pages, each pte we tear down maps 1GB.

A hot unplug of one 256MB memory block results in 768MB of memory
getting unintentionally unmapped. At this point we are likely to oops.

Fix this by increasing our memory block size to 1GB on PowerNV radix
hosts.

Fixes: 4b5d62ca17a1 ("powerpc/mm: add radix__remove_section_mapping()")
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/platforms/powernv/setup.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -272,7 +272,15 @@ static void pnv_kexec_cpu_down(int crash
 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
 static unsigned long pnv_memory_block_size(void)
 {
-	return 256UL * 1024 * 1024;
+	/*
+	 * We map the kernel linear region with 1GB large pages on radix. For
+	 * memory hot unplug to work our memory block size must be at least
+	 * this size.
+	 */
+	if (radix_enabled())
+		return 1UL * 1024 * 1024 * 1024;
+	else
+		return 256UL * 1024 * 1024;
 }
 #endif
 


Patches currently in stable-queue which might be from anton@samba.org are

queue-4.13/powerpc-powernv-increase-memory-block-size-to-1gb-on-radix.patch