powerpc/powernv: copy/paste - Mask XERS0 bit in CR

[Michael Ellerman]

Hi Haren,

Haren Myneni <haren at linux.vnet.ibm.com> writes:
>     
> NX can set 3rd bit in CR register for XER[SO] (Summation overflow)
> which is not related to paste request. The current paste function
> returns failure for the successful request when this bit is set.
> So mask this bit and check the proper return status.
>
> Fixes: 2392c8c8c045 ("powerpc/powernv/vas: Define copy/paste interfaces")
> Cc: stable at vger.kernel.org # v4.14+    
> Signed-off-by: Haren Myneni <haren at us.ibm.com>
>
> diff --git a/arch/powerpc/platforms/powernv/copy-paste.h b/arch/powerpc/platforms/powernv/copy-paste.h
> index c9a5036..82392e3 100644
> --- a/arch/powerpc/platforms/powernv/copy-paste.h
> +++ b/arch/powerpc/platforms/powernv/copy-paste.h
> @@ -9,7 +9,8 @@
>  #include <asm/ppc-opcode.h>
>  
>  #define CR0_SHIFT	28
> -#define CR0_MASK	0xF
> +#define CR0_MASK	0xE /* 3rd bit undefined or set for XER[SO] */
> +
>  /*
>   * Copy/paste instructions:
>   *

Unfortunately this no longer applies to my next branch, because those
macros have been moved out of this header as part of an unrelated patch.

The following patch should work instead, can you please confirm by
testing it?

diff --git a/arch/powerpc/platforms/powernv/copy-paste.h b/arch/powerpc/platforms/powernv/copy-paste.h
index 3fa62de96d9c..c46a326776cf 100644
--- a/arch/powerpc/platforms/powernv/copy-paste.h
+++ b/arch/powerpc/platforms/powernv/copy-paste.h
@@ -41,5 +41,7 @@ static inline int vas_paste(void *paste_address, int offset)
 		: "b" (offset), "b" (paste_address)
 		: "memory", "cr0");
 
-	return (cr >> CR0_SHIFT) & CR0_MASK;
+
+	/* We mask with 0xE to ignore SO */
+	return (cr >> CR0_SHIFT) & 0xE;
 }


cheers