[patch 16/30] x86_64: Fix FPU corruption

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



-stable review patch.  If anyone has any objections, please let us know.
------------------

From: Andi Kleen <[email protected]>

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: [email protected]
Signed-off-by: Andi Kleen <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
---
 arch/x86_64/kernel/process.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- linux-2.6.18.2.orig/arch/x86_64/kernel/process.c
+++ linux-2.6.18.2/arch/x86_64/kernel/process.c
@@ -571,6 +571,9 @@ __switch_to(struct task_struct *prev_p, 
 		prev->gsindex = gsindex;
 	}
 
+	/* Must be after DS reload */
+	unlazy_fpu(prev_p);
+
 	/* 
 	 * Switch the PDA and FPU contexts.
 	 */
@@ -578,10 +581,6 @@ __switch_to(struct task_struct *prev_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,
 		  task_stack_page(next_p) + THREAD_SIZE - PDA_STACKOFFSET);
 

--
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux