Messages in this thread | | | Date | Fri, 15 May 2015 11:54:59 -0400 | From | Boris Ostrovsky <> | Subject | Re: [RFC 10/23] xen/biomerge: WORKAROUND always says the biovec are not mergeable |
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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
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