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authorAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>2020-07-09 16:19:25 +0300
committerMichael Ellerman <mpe@ellerman.id.au>2020-07-20 15:57:56 +0300
commitaf9d00e93a4f062c5f160325d7b8f33336f6744e (patch)
tree0cfa8331eb72702dfbb8568126a2b3c0d5ad7422 /arch/powerpc/platforms
parentd6d6ebfc5dbb4008be21baa4ec2ad45606578966 (diff)
downloadlinux-af9d00e93a4f062c5f160325d7b8f33336f6744e.tar.xz
powerpc/mm/radix: Create separate mappings for hot-plugged memory
To enable memory unplug without splitting kernel page table mapping, we force the max mapping size to the LMB size. LMB size is the unit in which hypervisor will do memory add/remove operation. Pseries systems supports max LMB size of 256MB. Hence on pseries, we now end up mapping memory with 2M page size instead of 1G. To improve that we want hypervisor to hint the kernel about the hotplug memory range. That was added that as part of commit b6eca183e23e ("powerpc/kernel: Enables memory hot-remove after reboot on pseries guests") But PowerVM doesn't provide that hint yet. Once we get PowerVM updated, we can then force the 2M mapping only to hot-pluggable memory region using memblock_is_hotpluggable(). Till then let's depend on LMB size for finding the mapping page size for linear range. With this change KVM guest will also be doing linear mapping with 2M page size. The actual TLB benefit of mapping guest page table entries with hugepage size can only be materialized if the partition scoped entries are also using the same or higher page size. A guest using 1G hugetlbfs backing guest memory can have a performance impact with the above change. Signed-off-by: Bharata B Rao <bharata@linux.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> [mpe: Fold in fix from Aneesh spotted by lkp@intel.com] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200709131925.922266-5-aneesh.kumar@linux.ibm.com
Diffstat (limited to 'arch/powerpc/platforms')
-rw-r--r--arch/powerpc/platforms/powernv/setup.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 3bc188da82ba..7fcb88623081 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -399,7 +399,15 @@ static void pnv_kexec_cpu_down(int crash_shutdown, int secondary)
#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 radix_mem_block_size;
+ else
+ return 256UL * 1024 * 1024;
}
#endif