Re: [PATCH] xen: arm: invalidate caches after map_domain_page done

[Julien Grall <julien.grall@linaro.org>]

On 01/08/14 16:06, Andrii Tseglytskyi wrote:
> Looks like I see where is the issue:
> After mapping done kernel driver calls flush_tlb_all() function, which
> just invalidates cache, it does the similar command, as the following

flush_tlb_all doesn't invalidate the cache but the TLB.

> Xen macros:
>
> #define DTLBIALL        p15,0,c8,c6,0   /* Invalidate data TLB */
>
> Then after mapping done, remoteproc_iommu starts translation, calls
> map_domain_page() -> flush_xen_data_tlb_range_va_local(),
> which is described with following macros:
>
> #define TLBIMVAH        p15,4,c8,c7,1   /* Invalidate Unified Hyp. TLB by MVA */
>
> So, I got 2 invalidates and no cleans. And when I started using
> clean_and_invalidate_xen_dcache_va_range() I got both:
>
> #define DCCIMVAC        p15,0,c7,c14,1  /* Data cache clean and
> invalidate by MVA */
>
> I need both - clean and invalidate. If I don't have clean - data may
> still present in cache and not flushed to RAM - I will see invalid
> data after map_domain_page() call

You seem to mix TLB and cache in your mail. If the page has been mapped 
with cache attribute (should be done by kmalloc), then it should not 
have any issue in Xen.

Your patch is removing the TLB flush and you are very lucky that Xen is 
still working correctly...

Regards,

-- 
Julien Grall