diff mbox series

[02/15] memblock: Declare scratch memory as CMA

Message ID 20231213000452.88295-3-graf@amazon.com
State New
Headers
Series kexec: Allow preservation of ftrace buffers |

Commit Message

Alexander Graf Dec. 13, 2023, 12:04 a.m. UTC 
  When we finish populating our memory, we don't want to lose the scratch
region as memory we can use for useful data. Do do that, we mark it as
CMA memory. That means that any allocation within it only happens with
movable memory which we can then happily discard for the next kexec.

That way we don't lose the scratch region's memory anymore for
allocations after boot.

Signed-off-by: Alexander Graf <graf@amazon.com>
---
 mm/memblock.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

Comments

kernel test robot Dec. 13, 2023, 11:32 a.m. UTC | #1 
Hi Alexander,

kernel test robot noticed the following build warnings:

[auto build test WARNING on tip/x86/core]
[also build test WARNING on arm64/for-next/core akpm-mm/mm-everything linus/master v6.7-rc5 next-20231213]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Alexander-Graf/mm-memblock-Add-support-for-scratch-memory/20231213-080941
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/20231213000452.88295-3-graf%40amazon.com
patch subject: [PATCH 02/15] memblock: Declare scratch memory as CMA
config: arc-allnoconfig (https://download.01.org/0day-ci/archive/20231213/202312131930.gMiphjju-lkp@intel.com/config)
compiler: arc-elf-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231213/202312131930.gMiphjju-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202312131930.gMiphjju-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/memblock.c:2153:13: warning: 'reserve_scratch_mem' defined but not used [-Wunused-function]
    2153 | static void reserve_scratch_mem(phys_addr_t start, phys_addr_t end)
         |             ^~~~~~~~~~~~~~~~~~~


vim +/reserve_scratch_mem +2153 mm/memblock.c

  2152	
> 2153	static void reserve_scratch_mem(phys_addr_t start, phys_addr_t end)
  2154	{
  2155	#ifdef CONFIG_MEMBLOCK_SCRATCH
  2156		ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
  2157		ulong end_pfn = pageblock_align(PFN_UP(end));
  2158		ulong pfn;
  2159	
  2160		for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
  2161			/* Mark as CMA to prevent kernel allocations in it */
  2162			set_pageblock_migratetype(pfn_to_page(pfn), MIGRATE_CMA);
  2163		}
  2164	#endif
  2165	}
  2166
diff mbox series

Patch

diff --git a/mm/memblock.c b/mm/memblock.c
index e89e6c8f9d75..44741424dab7 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -16,6 +16,7 @@ 
 #include <linux/kmemleak.h>
 #include <linux/seq_file.h>
 #include <linux/memblock.h>
+#include <linux/page-isolation.h>
 
 #include <asm/sections.h>
 #include <linux/io.h>
@@ -1100,10 +1101,6 @@  static bool should_skip_region(struct memblock_type *type,
 	if ((flags & MEMBLOCK_SCRATCH) && !memblock_is_scratch(m))
 		return true;
 
-	/* Leave scratch memory alone after scratch-only phase */
-	if (!(flags & MEMBLOCK_SCRATCH) && memblock_is_scratch(m))
-		return true;
-
 	return false;
 }
 
@@ -2153,6 +2150,20 @@  static void __init __free_pages_memory(unsigned long start, unsigned long end)
 	}
 }
 
+static void reserve_scratch_mem(phys_addr_t start, phys_addr_t end)
+{
+#ifdef CONFIG_MEMBLOCK_SCRATCH
+	ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
+	ulong end_pfn = pageblock_align(PFN_UP(end));
+	ulong pfn;
+
+	for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
+		/* Mark as CMA to prevent kernel allocations in it */
+		set_pageblock_migratetype(pfn_to_page(pfn), MIGRATE_CMA);
+	}
+#endif
+}
+
 static unsigned long __init __free_memory_core(phys_addr_t start,
 				 phys_addr_t end)
 {
@@ -2214,6 +2225,17 @@  static unsigned long __init free_low_memory_core_early(void)
 
 	memmap_init_reserved_pages();
 
+#ifdef CONFIG_MEMBLOCK_SCRATCH
+	/*
+	 * Mark scratch mem as CMA before we return it. That way we ensure that
+	 * no kernel allocations happen on it. That means we can reuse it as
+	 * scratch memory again later.
+	 */
+	__for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
+			     MEMBLOCK_SCRATCH, &start, &end, NULL)
+		reserve_scratch_mem(start, end);
+#endif
+
 	/*
 	 * We need to use NUMA_NO_NODE instead of NODE_DATA(0)->node_id
 	 *  because in some case like Node0 doesn't have RAM installed