The patch titled
enforce noreplace-smp in alternative_instructions()
has been added to the -mm tree. Its filename is
enforce-noreplace-smp-in-alternative_instructions.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: enforce noreplace-smp in alternative_instructions()
From: Frederik Deweerdt <deweerdt@xxxxxxx>
arch/i386/kernel/alternative.c:alternative_instructions() doesn't
check for noreplace-smp before setting capability bits and freeing the
__smp_locks section.
Every call to alternatives_smp_unlock() checks for noreplace-smp
beforehand, so remove the check from there.
Without this patch, lguest crashes with
[ 0.131000] SMP alternatives: switching to UP code
lguest: bad stack page 0xc057a000
I added a dump_stack on the Host, which gives:
[124320.090946] [<c01052f8>] dump_trace+0x65/0x1de
[124320.090956] [<c010548b>] show_trace_log_lvl+0x1a/0x2f
[124320.090970] [<c0105ea4>] show_trace+0x12/0x14
[124320.090975] [<c0105fcd>] dump_stack+0x16/0x18
[124320.090980] [<f888032c>] pin_page+0x5f/0xa3 [lg]
[124320.090993] [<f8880654>] pin_stack_pages+0x3a/0x4a [lg]
[124320.091004] [<f888007e>] guest_pagetable_clear_all+0x12/0x15 [lg]
[124320.091013] [<f887f81a>] do_hcall+0xb1/0x1cb [lg]
[124320.091021] [<f887fbbe>] do_hypercalls+0x28a/0x2a0 [lg]
[124320.091029] [<f887f2a2>] run_guest+0x24/0x492 [lg]
[124320.091037] [<f8881b48>] read+0x83/0x8f [lg]
[124320.091048] [<c0175a77>] vfs_read+0x8e/0x117
[124320.091054] [<c0175e99>] sys_read+0x3d/0x61
[124320.091059] [<c0104166>] sysenter_past_esp+0x6b/0xb5
[124320.091065] [<ffffe410>] 0xffffe410
[124320.091069] =======================
(akpm: it's unclear to me why this happens, and how the patch fixed it)
Signed-off-by: Frederik Deweerdt <frederik.deweerdt@xxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/i386/kernel/alternative.c | 5 +----
1 files changed, 1 insertion(+), 4 deletions(-)
diff -puN arch/i386/kernel/alternative.c~enforce-noreplace-smp-in-alternative_instructions arch/i386/kernel/alternative.c
--- a/arch/i386/kernel/alternative.c~enforce-noreplace-smp-in-alternative_instructions
+++ a/arch/i386/kernel/alternative.c
@@ -221,9 +221,6 @@ static void alternatives_smp_unlock(u8 *
u8 **ptr;
char insn[1];
- if (noreplace_smp)
- return;
-
add_nops(insn, 1);
for (ptr = start; ptr < end; ptr++) {
if (*ptr < text)
@@ -404,7 +401,7 @@ void __init alternative_instructions(voi
#endif
#ifdef CONFIG_SMP
- if (smp_alt_once) {
+ if (smp_alt_once && !noreplace_smp) {
if (1 == num_possible_cpus()) {
printk(KERN_INFO "SMP alternatives: switching to UP code\n");
set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
_
Patches currently in -mm which might be from deweerdt@xxxxxxx are
xtensa-consolec-remove-duplicate-include.patch
enforce-noreplace-smp-in-alternative_instructions.patch
revoke-core-code.patch
reiser4-sb_sync_inodes.patch
-
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