Re: [Xen-devel] [PATCH] mm: Scrub pages returned back to heap if MEMF_no_scrub is set

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.09.17 at 16:04, <boris.ostrovsky@xxxxxxxxxx> wrote:
> Set free_heap_pages()'s need_scrub to true if alloc_domheap_pages()
> returns pages back to heap as result of assign_pages() error when those
> pages were requested with MEMF_no_scrub flag.
> 
> We need to do this because there is a possibility that
> alloc_heap_pages() might clear buddy's PGC_need_scrubs flag without
> actually clearing the page.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
> We are declaring a likely clean (or almost clean) chunk to be dirty. Since
> this only happend on assign_pages() error I figured it would be acceptable.

I think that's fine, but let's wait a little to see whether others
have differing opinions.

> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -2227,7 +2227,7 @@ struct page_info *alloc_domheap_pages(
>      if ( d && !(memflags & MEMF_no_owner) &&
>           assign_pages(d, pg, order, memflags) )
>      {
> -        free_heap_pages(pg, order, false);
> +        free_heap_pages(pg, order, !!(memflags & MEMF_no_scrub));

No need for the !! (easily fixed while committing). With that
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

I take it this isn't related to the issue on ARM64 that Konrad has
found?

Jan


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