Re: [Xen-devel] [PATCH] xen/arm: fix affected memory range by dcache clean functions

[Julien Grall <julien.grall@xxxxxxx>]

Hi Stefano,

On 03/03/2017 01:15 AM, Stefano Stabellini wrote:
> clean_dcache_va_range and clean_and_invalidate_dcache_va_range don't
> calculate the range correctly when "end" is not cacheline aligned. As a
> result, the last cacheline is not skipped. Fix the issue by aligning the
> start address to the cacheline size.
>
> In addition, make the code simpler and faster in
> invalidate_dcache_va_range, by removing the module operation and using
> bitmasks instead.
>
> Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Reported-by: edgar.iglesias@xxxxxxxxxx
> CC: edgar.iglesias@xxxxxxxxxx
> ---
>  xen/include/asm-arm/page.h | 24 +++++++++++-------------
>  1 file changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
> index 86de0b6..4b46e88 100644
> --- a/xen/include/asm-arm/page.h
> +++ b/xen/include/asm-arm/page.h
> @@ -291,24 +291,20 @@ extern size_t cacheline_bytes;
>
>  static inline int invalidate_dcache_va_range(const void *p, unsigned long size)
>  {
> -    size_t off;
>      const void *end = p + size;
> +    size_t cacheline_mask = cacheline_bytes - 1;
>
>      dsb(sy);           /* So the CPU issues all writes to the range */
>
> -    off = (unsigned long)p % cacheline_bytes;
> -    if ( off )
> +    if ( (uintptr_t)p & cacheline_mask )
>      {
> -        p -= off;
> +        p = (void *)((uintptr_t)p & ~cacheline_mask);
>          asm volatile (__clean_and_invalidate_dcache_one(0) : : "r" (p));
>          p += cacheline_bytes;
> -        size -= cacheline_bytes - off;
It would have been nice to explain in the commit message that you 
removed the adjustment of the size because the variable is not used 
later on.
With that:

Reviewed-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,

--
Julien Grall

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