Re: [PATCH v5 1/5] mm: page_alloc: remain memblock_next_valid_pfn() on arm and arm64
From: Jia He
Date: Mon Apr 02 2018 - 03:49:54 EST
On 4/2/2018 2:55 PM, Ard Biesheuvel Wrote:
On 2 April 2018 at 04:30, Jia He <hejianet@xxxxxxxxx> wrote:
Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
where possible") optimized the loop in memmap_init_zone(). But it causes
possible panic bug. So Daniel Vacek reverted it later.
But as suggested by Daniel Vacek, it is fine to using memblock to skip
gaps and finding next valid frame with CONFIG_HAVE_ARCH_PFN_VALID.
On arm and arm64, memblock is used by default. But generic version of
pfn_valid() is based on mem sections and memblock_next_valid_pfn() does
not always return the next valid one but skips more resulting in some
valid frames to be skipped (as if they were invalid). And that's why
kernel was eventually crashing on some !arm machines.
And as verified by Eugeniu Rosca, arm can benifit from commit
b92df1de5d28. So remain the memblock_next_valid_pfn on arm{,64} and move
the related codes to arm64 arch directory.
Suggested-by: Daniel Vacek <neelx@xxxxxxxxxx>
Signed-off-by: Jia He <jia.he@xxxxxxxxxxxxxxxx>
Hello Jia,
Apologies for chiming in late.
no problem, thanks for your comments ;-)
If we are going to rearchitect this, I'd rather we change the loop in
memmap_init_zone() so that we skip to the next valid PFN directly
rather than skipping to the last invalid PFN so that the pfn++ in the
hmm... Maybe this macro name makes you confused
pfn = skip_to_last_invalid_pfn(pfn);
how about skip_to_next_valid_pfn?
for () results in the next value. Can we replace the pfn++ there with
a function calls that defaults to 'return pfn + 1', but does the skip
for architectures that implement it?
I am not sure I understand your question here.
With this patch, on !arm arches, skip_to_last_invalid_pfn is equal to
(pfn), and will be increased
when for{} loop continue. We only *skip* to the start pfn of next valid
region when
CONFIG_HAVE_MEMBLOCK and CONFIG_HAVE_ARCH_PFN_VALID(arm/arm64 supports
both).
--
Cheers,
Jia
---
arch/arm/include/asm/page.h | 2 ++
arch/arm/mm/init.c | 31 ++++++++++++++++++++++++++++++-
arch/arm64/include/asm/page.h | 2 ++
arch/arm64/mm/init.c | 31 ++++++++++++++++++++++++++++++-
include/linux/mmzone.h | 1 +
mm/page_alloc.c | 4 +++-
6 files changed, 68 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h
index 4355f0e..489875c 100644
--- a/arch/arm/include/asm/page.h
+++ b/arch/arm/include/asm/page.h
@@ -158,6 +158,8 @@ typedef struct page *pgtable_t;
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
extern int pfn_valid(unsigned long);
+extern unsigned long memblock_next_valid_pfn(unsigned long pfn);
+#define skip_to_last_invalid_pfn(pfn) (memblock_next_valid_pfn(pfn) - 1)
#endif
#include <asm/memory.h>
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index a1f11a7..0fb85ca 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -198,7 +198,36 @@ int pfn_valid(unsigned long pfn)
return memblock_is_map_memory(__pfn_to_phys(pfn));
}
EXPORT_SYMBOL(pfn_valid);
-#endif
+
+/* HAVE_MEMBLOCK is always enabled on arm */
+unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
+{
+ struct memblock_type *type = &memblock.memory;
+ unsigned int right = type->cnt;
+ unsigned int mid, left = 0;
+ phys_addr_t addr = PFN_PHYS(++pfn);
+
+ do {
+ mid = (right + left) / 2;
+
+ if (addr < type->regions[mid].base)
+ right = mid;
+ else if (addr >= (type->regions[mid].base +
+ type->regions[mid].size))
+ left = mid + 1;
+ else {
+ /* addr is within the region, so pfn is valid */
+ return pfn;
+ }
+ } while (left < right);
+
+ if (right == type->cnt)
+ return -1UL;
+ else
+ return PHYS_PFN(type->regions[right].base);
+}
+EXPORT_SYMBOL(memblock_next_valid_pfn);
+#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
#ifndef CONFIG_SPARSEMEM
static void __init arm_memory_present(void)
diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
index 60d02c8..e57d3f2 100644
--- a/arch/arm64/include/asm/page.h
+++ b/arch/arm64/include/asm/page.h
@@ -39,6 +39,8 @@ typedef struct page *pgtable_t;
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
extern int pfn_valid(unsigned long);
+extern unsigned long memblock_next_valid_pfn(unsigned long pfn);
+#define skip_to_last_invalid_pfn(pfn) (memblock_next_valid_pfn(pfn) - 1)
#endif
#include <asm/memory.h>
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 00e7b90..13e43ff 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -290,7 +290,36 @@ int pfn_valid(unsigned long pfn)
return memblock_is_map_memory(pfn << PAGE_SHIFT);
}
EXPORT_SYMBOL(pfn_valid);
-#endif
+
+/* HAVE_MEMBLOCK is always enabled on arm64 */
+unsigned long __init_memblock memblock_next_valid_pfn(unsigned long pfn)
+{
+ struct memblock_type *type = &memblock.memory;
+ unsigned int right = type->cnt;
+ unsigned int mid, left = 0;
+ phys_addr_t addr = PFN_PHYS(++pfn);
+
+ do {
+ mid = (right + left) / 2;
+
+ if (addr < type->regions[mid].base)
+ right = mid;
+ else if (addr >= (type->regions[mid].base +
+ type->regions[mid].size))
+ left = mid + 1;
+ else {
+ /* addr is within the region, so pfn is valid */
+ return pfn;
+ }
+ } while (left < right);
+
+ if (right == type->cnt)
+ return -1UL;
+ else
+ return PHYS_PFN(type->regions[right].base);
+}
+EXPORT_SYMBOL(memblock_next_valid_pfn);
+#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
#ifndef CONFIG_SPARSEMEM
static void __init arm64_memory_present(void)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index d797716..f9c0c46 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1245,6 +1245,7 @@ static inline int pfn_valid(unsigned long pfn)
return 0;
return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
}
+#define skip_to_last_invalid_pfn(pfn) (pfn)
#endif
static inline int pfn_present(unsigned long pfn)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c19f5ac..30f7d76 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5483,8 +5483,10 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
if (context != MEMMAP_EARLY)
goto not_early;
- if (!early_pfn_valid(pfn))
+ if (!early_pfn_valid(pfn)) {
+ pfn = skip_to_last_invalid_pfn(pfn);
continue;
+ }
if (!early_pfn_in_nid(pfn, nid))
continue;
if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))
--
2.7.4