2009-02-09 20:05:46 +00:00
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#include <linux/bio.h>
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#include <linux/io.h>
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2012-01-18 23:24:31 +00:00
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#include <linux/export.h>
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2009-02-09 20:05:46 +00:00
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#include <xen/page.h>
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bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
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const struct bio_vec *vec2)
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{
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2015-05-11 12:44:21 +00:00
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#if XEN_PAGE_SIZE == PAGE_SIZE
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xen: Make clear that swiotlb and biomerge are dealing with DMA address
The swiotlb is required when programming a DMA address on ARM when a
device is not protected by an IOMMU.
In this case, the DMA address should always be equal to the machine address.
For DOM0 memory, Xen ensure it by have an identity mapping between the
guest address and host address. However, when mapping a foreign grant
reference, the 1:1 model doesn't work.
For ARM guest, most of the callers of pfn_to_mfn expects to get a GFN
(Guest Frame Number), i.e a PFN (Page Frame Number) from the Linux point
of view given that all ARM guest are auto-translated.
Even though the name pfn_to_mfn is misleading, we need to ensure that
those caller get a GFN and not by mistake a MFN. In pratical, I haven't
seen error related to this but we should fix it for the sake of
correctness.
In order to fix the implementation of pfn_to_mfn on ARM in a follow-up
patch, we have to introduce new helpers to return the DMA from a PFN and
the invert.
On x86, the new helpers will be an alias of pfn_to_mfn and mfn_to_pfn.
The helpers will be used in swiotlb and xen_biovec_phys_mergeable.
This is necessary in the latter because we have to ensure that the
biovec code will not try to merge a biovec using foreign page and
another using Linux memory.
Lastly, the helper mfn_to_local_pfn has been renamed to bfn_to_local_pfn
given that the only usage was in swiotlb.
Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2015-08-07 16:34:35 +00:00
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unsigned long bfn1 = pfn_to_bfn(page_to_pfn(vec1->bv_page));
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unsigned long bfn2 = pfn_to_bfn(page_to_pfn(vec2->bv_page));
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2009-02-09 20:05:46 +00:00
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xen: fix bio vec merging
The current test for bio vec merging is not fully accurate and can be
tricked into merging bios when certain grant combinations are used.
The result of these malicious bio merges is a bio that extends past
the memory page used by any of the originating bios.
Take into account the following scenario, where a guest creates two
grant references that point to the same mfn, ie: grant 1 -> mfn A,
grant 2 -> mfn A.
These references are then used in a PV block request, and mapped by
the backend domain, thus obtaining two different pfns that point to
the same mfn, pfn B -> mfn A, pfn C -> mfn A.
If those grants happen to be used in two consecutive sectors of a disk
IO operation becoming two different bios in the backend domain, the
checks in xen_biovec_phys_mergeable will succeed, because bfn1 == bfn2
(they both point to the same mfn). However due to the bio merging,
the backend domain will end up with a bio that expands past mfn A into
mfn A + 1.
Fix this by making sure the check in xen_biovec_phys_mergeable takes
into account the offset and the length of the bio, this basically
replicates whats done in __BIOVEC_PHYS_MERGEABLE using mfns (bus
addresses). While there also remove the usage of
__BIOVEC_PHYS_MERGEABLE, since that's already checked by the callers
of xen_biovec_phys_mergeable.
CC: stable@vger.kernel.org
Reported-by: "Jan H. Schönherr" <jschoenh@amazon.de>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2017-07-18 14:01:00 +00:00
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return bfn1 + PFN_DOWN(vec1->bv_offset + vec1->bv_len) == bfn2;
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2015-05-11 12:44:21 +00:00
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#else
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/*
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* XXX: Add support for merging bio_vec when using different page
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* size in Xen and Linux.
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*/
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return 0;
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#endif
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2009-02-09 20:05:46 +00:00
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}
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2011-11-04 19:41:27 +00:00
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EXPORT_SYMBOL(xen_biovec_phys_mergeable);
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