Commit 53ecde0b authored by Anton Blanchard's avatar Anton Blanchard Committed by Michael Ellerman
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powerpc/powernv: Increase memory block size to 1GB on radix

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

Fixes: 4b5d62ca

 ("powerpc/mm: add radix__remove_section_mapping()")
Cc: # v4.11+
Signed-off-by: default avatarAnton Blanchard <>
Signed-off-by: default avatarMichael Ellerman <>
parent 7c6a4f3b
......@@ -272,7 +272,15 @@ static void pnv_kexec_cpu_down(int crash_shutdown, int secondary)
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;
return 256UL * 1024 * 1024;
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