From mboxrd@z Thu Jan 1 00:00:00 1970 From: boris.ostrovsky@oracle.com (Boris Ostrovsky) Date: Fri, 15 May 2015 11:54:59 -0400 Subject: [RFC 10/23] xen/biomerge: WORKAROUND always says the biovec are not mergeable In-Reply-To: <1431622863-28575-11-git-send-email-julien.grall@citrix.com> References: <1431622863-28575-1-git-send-email-julien.grall@citrix.com> <1431622863-28575-11-git-send-email-julien.grall@citrix.com> Message-ID: <555616D3.7060603@oracle.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 > Cc: Konrad Rzeszutek Wilk > Cc: Boris Ostrovsky > Cc: David Vrabel > --- > 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