trim.bottom trims the wrong entry

This was a fun one to track down. I was trying to provide a fake SRAT table so that I could start working on some more ccNUMA issues on a non-NUMA tiger box, but my kernel kept dying while running scripts out of /etc/init.d/*

I found I was getting an MCA while executing an lfetch.excl in clear_page_tables(), the address that was being fetched was 0xe0000000000a00e8, which is non-cacheable VGA memory on Tiger.

Root cause was the "trim" code in efi_memmap_walk() had failed to trim away all the blocks of memory in the bottom granule when it had seen the memory hole there, so the kernel had managed to allocate a page at 0x9c000 as a page table, and when the process using it ended, the cleanup code prefetched off the end of the page, and into the VGA memory, causing an MCA.

The problem is that efi_memmap_walk() repeatedly trims the same entry, instead of trimming each of the entries in the granule.

-Tony

diff -ru a/arch/ia64/kernel/efi.c b/arch/ia64/kernel/efi.c
@@ -324,7 +324,7 @@
 				check_md = q;
 
 				if (check_md->attribute & EFI_MEMORY_WB)
-					trim_bottom(md, granule_addr);
+					trim_bottom(check_md, granule_addr);
 
 				if (check_md->phys_addr < granule_addr)
 					continue;

I applied this patch for 2.4. Thanks!

#### AUTHOR [email protected]
#### COMMENT START
### Comments for ChangeSet
ia64: Trim granules correctly in efi_memmap_walk()

This was a fun one to track down. I was trying to provide a fake SRAT table so that I could start working on some more ccNUMA issues on a non-NUMA tiger box, but my kernel kept dying while running scripts out of /etc/init.d/*

I found I was getting an MCA while executing an lfetch.excl in clear_page_tables(), the address that was being fetched was 0xe0000000000a00e8, which is non-cacheable VGA memory on Tiger.

Root cause was the "trim" code in efi_memmap_walk() had failed to trim away all the blocks of memory in the bottom granule when it had seen the memory hole there, so the kernel had managed to allocate a page at 0x9c000 as a page table, and when the process using it ended, the cleanup code prefetched off the end of the page, and into the VGA memory, causing an MCA.

The problem is that efi_memmap_walk() repeatedly trims the same entry, instead of trimming each of the entries in the granule. ### Comments for arch/ia64/kernel/efi.c (efi_memmap_walk): Trim entries from the correct granule. #### COMMENT END

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher. # This patch includes the following deltas:
# ChangeSet 1.1086 -> 1.1087
# arch/ia64/kernel/efi.c 1.13 -> 1.14
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/08/28 [email protected] 1.1087
# tony's fix.
# --------------------------------------------
#

diff -Nru a/arch/ia64/kernel/efi.c b/arch/ia64/kernel/efi.c
@@ -324,7 +324,7 @@
 				check_md = q;
 
 				if (check_md->attribute & EFI_MEMORY_WB)
-					trim_bottom(md, granule_addr);
+					trim_bottom(check_md, granule_addr);
 
 				if (check_md->phys_addr < granule_addr)
 					continue;

Tony> This was a fun one to track down.

Ouch. I can only imagine...

Tony> The problem is that efi_memmap_walk() repeatedly trims the Tony> same entry, instead of trimming each of the entries in the Tony> granule.

Applied.

Thanks,

	--david