lkml.org 
[lkml]   [2015]   [May]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC 10/23] xen/biomerge: WORKAROUND always says the biovec are not mergeable
On 05/14/2015 01:00 PM, Julien Grall wrote:
> When Linux is using 64K page granularity, every page will be slipt in
> multiple non-contiguous 4K MFN.
>
> I'm not sure how to handle efficiently the check to know whether we can
> merge 2 biovec with a such case. So for now, always says that biovec are
> not mergeable.
>
> Signed-off-by: Julien Grall <julien.grall@citrix.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: David Vrabel <david.vrabel@citrix.com>
> ---
> drivers/xen/biomerge.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/xen/biomerge.c b/drivers/xen/biomerge.c
> index 0edb91c..20387c2 100644
> --- a/drivers/xen/biomerge.c
> +++ b/drivers/xen/biomerge.c
> @@ -9,6 +9,9 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
> unsigned long mfn1 = pfn_to_mfn(page_to_pfn(vec1->bv_page));
> unsigned long mfn2 = pfn_to_mfn(page_to_pfn(vec2->bv_page));
>
> + /* TODO: Implement it correctly */
> + return 0;
> +
> return __BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&
> ((mfn1 == mfn2) || ((mfn1+1) == mfn2));
> }


I think this is a bit too blunt. Perhaps check first whether page sizes
are different in the hypervisor and the guest?

(And I am not sure we need __BIOVEC_PHYS_MERGEABLE() test here as it is
already checked by BIOVEC_PHYS_MERGEABLE() which appears to be the only
user of xen_biovec_phys_mergeable())


-boris


\
 
 \ /
  Last update: 2015-05-15 19:01    [W:0.597 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site