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authorAndi Kleen <ak@suse.de>2006-10-05 18:47:22 +0200
committerAndi Kleen <andi@basil.nowhere.org>2006-10-05 18:47:22 +0200
commit0a5ace2ab08d45cd78d7ef0067cdcd5c812ac54f (patch)
treea4da5e79010de2391ee92d6a71b2a7217ed68d61
parent51ec28e1b2cb267a09a0b8eac1ccf8d61b7268bf (diff)
[PATCH] x86-64: Fix FPU corruption
This reverts an earlier patch that was found to cause FPU state corruption. I think the corruption happens because unlazy_fpu() can cause FPU exceptions and when it happens after the current switch some processing would affect the state in the wrong process. Thanks to Douglas Crosher and Tom Hughes for testing. Cc: jbeulich@novell.com Signed-off-by: Andi Kleen <ak@suse.de>
-rw-r--r--arch/x86_64/kernel/process.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c
index de10cb8a2c9..5e95b257ee2 100644
--- a/arch/x86_64/kernel/process.c
+++ b/arch/x86_64/kernel/process.c
@@ -615,6 +615,9 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
prev->gsindex = gsindex;
}
+ /* Must be after DS reload */
+ unlazy_fpu(prev_p);
+
/*
* Switch the PDA and FPU contexts.
*/
@@ -622,10 +625,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
write_pda(oldrsp, next->userrsp);
write_pda(pcurrent, next_p);
- /* This must be here to ensure both math_state_restore() and
- kernel_fpu_begin() work consistently.
- And the AMD workaround requires it to be after DS reload. */
- unlazy_fpu(prev_p);
write_pda(kernelstack,
(unsigned long)task_stack_page(next_p) + THREAD_SIZE - PDA_STACKOFFSET);
#ifdef CONFIG_CC_STACKPROTECTOR