Re: [Xen-devel] [PATCH v4 4/7] xen/x86: introduce more cache maintenance operations

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.10.14 at 13:43, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> +void clean_and_invalidate_dcache_va_range(const void *p, unsigned long size)
> +{
> +    int order = get_order_from_bytes(size);

unsigned int if the variable is really needed.

> +    flush_area_local(p, FLUSH_CACHE|FLUSH_ORDER(order));
> +}

Overall I wonder whether not making this an inline function is really
appropriate.

Oh, and then I may have slightly misguided you: The caller you're
adding for this wants to be able to clean/invalidate sub-page chunks,
which this interface doesn't allow. This isn't a problem unless the
operation gets done frequently and always degenerates to wbinvd().
At the very least I'd suggest adding a comment saying that sub-page
granularity support would need to be added if necessary here.

> --- a/xen/include/asm-x86/page.h
> +++ b/xen/include/asm-x86/page.h
> @@ -344,8 +344,13 @@ static inline uint32_t cacheattr_to_pte_flags(uint32_t 
> cacheattr)
>      return ((cacheattr & 4) << 5) | ((cacheattr & 3) << 3);
>  }
>  
> -/* No cache maintenance required on x86 architecture. */
>  static inline void flush_page_to_ram(unsigned long mfn) {}
> +static inline void invalidate_dcache_va_range(const void *p, unsigned long 
> size) {}

This should fail, not appear to succeed. We just can't do what is being
requested.

Jan


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