Hi Greg,

On Thu, May 16, 2013 at 05:49:18PM -0400, [email protected] wrote:
> 
> This is a note to let you know that I've just added the patch titled
> 
>     powerpc/kexec: Fix kexec when using VMX optimised memcpy
> 
> to the 3.4-stable tree which can be found at:
>     
> http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      powerpc-kexec-fix-kexec-when-using-vmx-optimised-memcpy.patch
> and it can be found in the queue-3.4 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <[email protected]> know about it.

I'm not sure this commit should be queued for 3.0 and 3.4, as it is
tagged for stable 3.6+.

Cheers,
--
Luis

>
> 
> From 79c66ce8f6448a3295a32efeac88c9debd7f7094 Mon Sep 17 00:00:00 2001
> From: Anton Blanchard <[email protected]>
> Date: Sun, 12 May 2013 15:04:53 +0000
> Subject: powerpc/kexec: Fix kexec when using VMX optimised memcpy
> 
> From: Anton Blanchard <[email protected]>
> 
> commit 79c66ce8f6448a3295a32efeac88c9debd7f7094 upstream.
> 
> commit b3f271e86e5a (powerpc: POWER7 optimised memcpy using VMX and
> enhanced prefetch) uses VMX when it is safe to do so (ie not in
> interrupt). It also looks at the task struct to decide if we have to
> save the current tasks' VMX state.
> 
> kexec calls memcpy() at a point where the task struct may have been
> overwritten by the new kexec segments. If it has been overwritten
> then when memcpy -> enable_altivec looks up current->thread.regs->msr
> we get a cryptic oops or lockup.
> 
> I also notice we aren't initialising thread_info->cpu, which means
> smp_processor_id is broken. Fix that too.
> 
> Signed-off-by: Anton Blanchard <[email protected]>
> Signed-off-by: Benjamin Herrenschmidt <[email protected]>
> Signed-off-by: Greg Kroah-Hartman <[email protected]>
> 
> ---
>  arch/powerpc/kernel/machine_kexec_64.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> --- a/arch/powerpc/kernel/machine_kexec_64.c
> +++ b/arch/powerpc/kernel/machine_kexec_64.c
> @@ -17,6 +17,7 @@
>  #include <linux/errno.h>
>  #include <linux/kernel.h>
>  #include <linux/cpu.h>
> +#include <linux/hardirq.h>
>  
>  #include <asm/page.h>
>  #include <asm/current.h>
> @@ -335,10 +336,13 @@ void default_machine_kexec(struct kimage
>       pr_debug("kexec: Starting switchover sequence.\n");
>  
>       /* switch to a staticly allocated stack.  Based on irq stack code.
> +      * We setup preempt_count to avoid using VMX in memcpy.
>        * XXX: the task struct will likely be invalid once we do the copy!
>        */
>       kexec_stack.thread_info.task = current_thread_info()->task;
>       kexec_stack.thread_info.flags = 0;
> +     kexec_stack.thread_info.preempt_count = HARDIRQ_OFFSET;
> +     kexec_stack.thread_info.cpu = current_thread_info()->cpu;
>  
>       /* We need a static PACA, too; copy this CPU's PACA over and switch to
>        * it.  Also poison per_cpu_offset to catch anyone using non-static
> 
> 
> Patches currently in stable-queue which might be from [email protected] are
> 
> queue-3.4/powerpc-kexec-fix-kexec-when-using-vmx-optimised-memcpy.patch
> --
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