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.gr...@citrix.com> Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com> Cc: Boris Ostrovsky <boris.ostrov...@oracle.com> Cc: David Vrabel <david.vra...@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())
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