Re: [PATCH 1/4] mm/page_alloc: always initialize memory map for the holes
From: Guenter Roeck
Date: Sat Jul 31 2021 - 15:11:30 EST
Hi,
On 7/31/21 11:30 AM, Mike Rapoport wrote:
On Sat, Jul 31, 2021 at 09:56:01AM -0700, Guenter Roeck wrote:
Hi,
On Wed, Jul 14, 2021 at 03:37:36PM +0300, Mike Rapoport wrote:
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Currently memory map for the holes is initialized only when SPARSEMEM
memory model is used. Yet, even with FLATMEM there could be holes in the
physical memory layout that have memory map entries.
For instance, the memory reserved using e820 API on i386 or
"reserved-memory" nodes in device tree would not appear in memblock.memory
and hence the struct pages for such holes will be skipped during memory map
initialization.
These struct pages will be zeroed because the memory map for FLATMEM
systems is allocated with memblock_alloc_node() that clears the allocated
memory. While zeroed struct pages do not cause immediate problems, the
correct behaviour is to initialize every page using __init_single_page().
Besides, enabling page poison for FLATMEM case will trigger
PF_POISONED_CHECK() unless the memory map is properly initialized.
Make sure init_unavailable_range() is called for both SPARSEMEM and FLATMEM
so that struct pages representing memory holes would appear as PG_Reserved
with any memory layout.
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
This patch causes microblaze petalogix-ml605 qemu emulations to fail
silently (no console output). Reverting it fixes the problem.
It appears that petalogix-ml605 memory starts at 0x50000, but microblaze's
pfn_valid does not reject pfns < ARCH_PFN_OFFSET.
This should fix the issue:
diff --git a/arch/microblaze/include/asm/page.h b/arch/microblaze/include/asm/page.h
index ce550978f4fc..4b8b2fa78fc5 100644
--- a/arch/microblaze/include/asm/page.h
+++ b/arch/microblaze/include/asm/page.h
@@ -112,8 +112,7 @@ extern int page_is_ram(unsigned long pfn);
# define page_to_phys(page) (page_to_pfn(page) << PAGE_SHIFT)
# define ARCH_PFN_OFFSET (memory_start >> PAGE_SHIFT)
-# define pfn_valid(pfn) ((pfn) < (max_mapnr + ARCH_PFN_OFFSET))
-
+# define pfn_valid(pfn) ((pfn) >= ARCH_PFN_OFFSET && (pfn) < (max_mapnr + ARCH_PFN_OFFSET))
# endif /* __ASSEMBLY__ */
#define virt_addr_valid(vaddr) (pfn_valid(virt_to_pfn(vaddr)))
Indeed, that does the trick.
Feel free to add
Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
to the patch.
Thanks,
Guenter
Guenter
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# bad: [d2a572bf593a57246827bd79c91fe2ee6b7af1f0] mm/page_alloc: always initialize memory map for the holes
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# first bad commit: [d2a572bf593a57246827bd79c91fe2ee6b7af1f0] mm/page_alloc: always initialize memory map for the holes