[PATCH] powerpc/mm: Limit resize_hpt_for_hotplug() call to hash guests only

[PATCH] powerpc/mm: Limit resize_hpt_for_hotplug() call to hash guests only

[Bharata B Rao]

During memory hotplug and unplug, resize_hpt_for_hotplug() gets called
for both hash and radix guests but it should be called only for hash
guests. Though the call does nothing in the radix guest case, it is
cleaner to push this call into hash specific memory hotplug routines.

Reported-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
---
Tested with memory hotplug and unplug for hash and radix KVM guests.

 arch/powerpc/include/asm/sparsemem.h  | 6 ------
 arch/powerpc/mm/book3s64/hash_utils.c | 8 +++++++-
 arch/powerpc/mm/mem.c                 | 5 -----
 3 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/include/asm/sparsemem.h b/arch/powerpc/include/asm/sparsemem.h
index c89b32443cff..1e6fa371cc38 100644
--- a/arch/powerpc/include/asm/sparsemem.h
+++ b/arch/powerpc/include/asm/sparsemem.h
@@ -17,12 +17,6 @@ extern int create_section_mapping(unsigned long start, unsigned long end,
 				  int nid, pgprot_t prot);
 extern int remove_section_mapping(unsigned long start, unsigned long end);
 
-#ifdef CONFIG_PPC_BOOK3S_64
-extern int resize_hpt_for_hotplug(unsigned long new_mem_size);
-#else
-static inline int resize_hpt_for_hotplug(unsigned long new_mem_size) { return 0; }
-#endif
-
 #ifdef CONFIG_NUMA
 extern int hot_add_scn_to_nid(unsigned long scn_addr);
 #else
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index 9fdabea04990..30a4a91d9987 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -785,7 +785,7 @@ static unsigned long __init htab_get_table_size(void)
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG
-int resize_hpt_for_hotplug(unsigned long new_mem_size)
+static int resize_hpt_for_hotplug(unsigned long new_mem_size)
 {
 	unsigned target_hpt_shift;
 
@@ -819,6 +819,8 @@ int hash__create_section_mapping(unsigned long start, unsigned long end,
 		return -1;
 	}
 
+	resize_hpt_for_hotplug(memblock_phys_mem_size());
+
 	rc = htab_bolt_mapping(start, end, __pa(start),
 			       pgprot_val(prot), mmu_linear_psize,
 			       mmu_kernel_ssize);
@@ -836,6 +838,10 @@ int hash__remove_section_mapping(unsigned long start, unsigned long end)
 	int rc = htab_remove_mapping(start, end, mmu_linear_psize,
 				     mmu_kernel_ssize);
 	WARN_ON(rc < 0);
+
+	if (resize_hpt_for_hotplug(memblock_phys_mem_size()) == -ENOSPC)
+		pr_warn("Hash collision while resizing HPT\n");
+
 	return rc;
 }
 #endif /* CONFIG_MEMORY_HOTPLUG */
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index c2c11eb8dcfc..9dafc636588f 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -127,8 +127,6 @@ int __ref arch_add_memory(int nid, u64 start, u64 size,
 	unsigned long nr_pages = size >> PAGE_SHIFT;
 	int rc;
 
-	resize_hpt_for_hotplug(memblock_phys_mem_size());
-
 	start = (unsigned long)__va(start);
 	rc = create_section_mapping(start, start + size, nid,
 				    params->pgprot);
@@ -161,9 +159,6 @@ void __ref arch_remove_memory(int nid, u64 start, u64 size,
 	 * hit that section of memory
 	 */
 	vm_unmap_aliases();
-
-	if (resize_hpt_for_hotplug(memblock_phys_mem_size()) == -ENOSPC)
-		pr_warn("Hash collision while resizing HPT\n");
 }
 #endif
 
-- 
2.26.2

Re: [PATCH] powerpc/mm: Limit resize_hpt_for_hotplug() call to hash guests only

[Michael Ellerman]

On Mon, 27 Jul 2020 15:27:04 +0530, Bharata B Rao wrote:
> During memory hotplug and unplug, resize_hpt_for_hotplug() gets called
> for both hash and radix guests but it should be called only for hash
> guests. Though the call does nothing in the radix guest case, it is
> cleaner to push this call into hash specific memory hotplug routines.

Applied to powerpc/next.

[1/1] powerpc/mm: Limit resize_hpt_for_hotplug() call to hash guests only
      https://git.kernel.org/powerpc/c/55548a86ebde2b3691b6a84baef1b02933408994

cheers