Messages in this thread | | | Date | Tue, 19 May 2015 15:16:01 +0100 | From | Julien Grall <> | Subject | Re: [RFC 10/23] xen/biomerge: WORKAROUND always says the biovec are not mergeable |
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Hi Boris,
On 15/05/15 16:54, Boris Ostrovsky wrote: > 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?
Sounds good.
> > (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())
I can send a patch to drop __BIOVEC_PHYS_MERGEABLE.
Regards,
-- Julien Grall
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