Re: [PATCH v2] powerpc: Allow flush_(inval_)dcache_range to work across ranges >4GB

[Michael Ellerman]

"Alastair D'Silva" <alastair@xxxxxxxxxxx> writes:

> From: Alastair D'Silva <alastair@xxxxxxxxxxx>
>
> The upstream commit:
> 22e9c88d486a ("powerpc/64: reuse PPC32 static inline flush_dcache_range()")
> has a similar effect, but since it is a rewrite of the assembler to C, is
> too invasive for stable. This patch is a minimal fix to address the issue in
> assembler.
>
> This patch applies cleanly to v5.2, v4.19 & v4.14.
>
> When calling flush_(inval_)dcache_range with a size >4GB, we were masking
> off the upper 32 bits, so we would incorrectly flush a range smaller
> than intended.
>
> This patch replaces the 32 bit shifts with 64 bit ones, so that
> the full size is accounted for.
>
> Changelog:
> v2
>   - Add related upstream commit
>
> Signed-off-by: Alastair D'Silva <alastair@xxxxxxxxxxx>
> ---
>  arch/powerpc/kernel/misc_64.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Acked-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>

cheers


> diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
> index 1ad4089dd110..d4d096f80f4b 100644
> --- a/arch/powerpc/kernel/misc_64.S
> +++ b/arch/powerpc/kernel/misc_64.S
> @@ -130,7 +130,7 @@ _GLOBAL_TOC(flush_dcache_range)
>  	subf	r8,r6,r4		/* compute length */
>  	add	r8,r8,r5		/* ensure we get enough */
>  	lwz	r9,DCACHEL1LOGBLOCKSIZE(r10)	/* Get log-2 of dcache block size */
> -	srw.	r8,r8,r9		/* compute line count */
> +	srd.	r8,r8,r9		/* compute line count */
>  	beqlr				/* nothing to do? */
>  	mtctr	r8
>  0:	dcbst	0,r6
> @@ -148,7 +148,7 @@ _GLOBAL(flush_inval_dcache_range)
>  	subf	r8,r6,r4		/* compute length */
>  	add	r8,r8,r5		/* ensure we get enough */
>  	lwz	r9,DCACHEL1LOGBLOCKSIZE(r10)/* Get log-2 of dcache block size */
> -	srw.	r8,r8,r9		/* compute line count */
> +	srd.	r8,r8,r9		/* compute line count */
>  	beqlr				/* nothing to do? */
>  	sync
>  	isync
> -- 
> 2.21.0