On 11/02/26 09:05, Ritesh Harjani (IBM) wrote:
Sourabh Jain <[email protected]> writes:
During a memory hot-remove event, the elfcorehdr is rebuilt to exclude
the removed memory. While updating the crash memory ranges for this
operation, the crash memory ranges array can become unsorted. This
happens because remove_mem_range() may split a memory range into two
parts and append the higher-address part as a separate range at the end
of the array.
So far, no issues have been observed due to the unsorted crash memory
ranges. However, this could lead to problems once crash memory range
removal is handled by generic code, as introduced in the upcoming
patches in this series.
Do you have the link of the discussion, to where you have pointed about,
what sort of problems this unsorted memory ranges might bring up with
the new patch series?
No, we didn’t discuss this anywhere. This occurred to me while I
was reviewing [1].
The issue is that [1] moves the exclusion of crashkernel reserved
memory into a generic function. With [1] included, the architecture
prepares the initial set of crash_mem ranges, and later the generic
function removes the crashkernel memory range from those crash_mem
ranges by calling crash_exclude_mem_range().
crash_exclude_mem_range() expects the crash_mem ranges to be sorted,
but that may not be true on powerpc if the ranges come from the
hotplug remove path, where remove_mem_range() is called to exclude
the hot-removed memory range.
[1]
https://lore.kernel.org/all/[email protected]/
Currently, powerpc uses a platform-specific function,
remove_mem_range(), to exclude hot-removed memory from the crash memory
ranges. This function performs the same task as the generic
crash_exclude_mem_range() in crash_core.c. The generic helper also
ensures that the crash memory ranges remain sorted. So remove the
redundant powerpc-specific implementation and instead call
crash_exclude_mem_range_guarded() (which internally calls
crash_exclude_mem_range()) to exclude the hot-removed memory ranges.
Cc: Andrew Morton <[email protected]>
Cc: Baoquan he <[email protected]>
Cc: Jinjie Ruan <[email protected]>
Cc: Hari Bathini <[email protected]>
Cc: Madhavan Srinivasan <[email protected]>
Cc: Mahesh Salgaonkar <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Ritesh Harjani (IBM) <[email protected]>
Cc: Shivang Upadhyay <[email protected]>
Cc: [email protected]
Signed-off-by: Sourabh Jain <[email protected]>
---
Requesting this patch to part of the below patch series.
https://lore.kernel.org/all/[email protected]/
---
arch/powerpc/include/asm/kexec_ranges.h | 4 +-
arch/powerpc/kexec/crash.c | 5 +-
arch/powerpc/kexec/ranges.c | 87 +------------------------
3 files changed, 7 insertions(+), 89 deletions(-)
diff --git a/arch/powerpc/include/asm/kexec_ranges.h
b/arch/powerpc/include/asm/kexec_ranges.h
index 14055896cbcb..ad95e3792d10 100644
--- a/arch/powerpc/include/asm/kexec_ranges.h
+++ b/arch/powerpc/include/asm/kexec_ranges.h
@@ -7,7 +7,9 @@
void sort_memory_ranges(struct crash_mem *mrngs, bool merge);
struct crash_mem *realloc_mem_ranges(struct crash_mem **mem_ranges);
int add_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
-int remove_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
+int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
+ unsigned long long mstart,
+ unsigned long long mend);
int get_exclude_memory_ranges(struct crash_mem **mem_ranges);
int get_reserved_memory_ranges(struct crash_mem **mem_ranges);
int get_crash_memory_ranges(struct crash_mem **mem_ranges);
diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c
index a325c1c02f96..31462e8415ff 100644
--- a/arch/powerpc/kexec/crash.c
+++ b/arch/powerpc/kexec/crash.c
@@ -431,7 +431,7 @@ static void update_crash_elfcorehdr(struct kimage *image,
struct memory_notify *
struct crash_mem *cmem = NULL;
struct kexec_segment *ksegment;
void *ptr, *mem, *elfbuf = NULL;
- unsigned long elfsz, memsz, base_addr, size;
+ unsigned long elfsz, memsz, base_addr, size, end;
ksegment = &image->segment[image->elfcorehdr_index];
mem = (void *) ksegment->mem;
@@ -450,7 +450,8 @@ static void update_crash_elfcorehdr(struct kimage *image,
struct memory_notify *
if (image->hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY) {
base_addr = PFN_PHYS(mn->start_pfn);
size = mn->nr_pages * PAGE_SIZE;
- ret = remove_mem_range(&cmem, base_addr, size);
+ end = base_addr - size - 1;
end should be "base_addr + size - 1", isn't it?
oops, my bad. I will fix it in v2.
Thanks for the review, Ritesh.
+ ret = crash_exclude_mem_range_guarded(&cmem, base_addr, end);
if (ret) {
pr_err("Failed to remove hot-unplugged memory from crash
memory ranges\n");
goto out;
-ritesh
