summaryrefslogtreecommitdiff
path: root/drivers/xen/biomerge.c
AgeCommit message (Collapse)Author
2015-10-23xen/biomerge: Don't allow biovec's to be merged when Linux is not using 4KB ↵Julien Grall
pages On ARM all dma-capable devices on a same platform may not be protected by an IOMMU. The DMA requests have to use the BFN (i.e MFN on ARM) in order to use correctly the device. While the DOM0 memory is allocated in a 1:1 fashion (PFN == MFN), grant mapping will screw this contiguous mapping. When Linux is using 64KB page granularitary, the page may be split accross multiple non-contiguous MFN (Xen is using 4KB page granularity). Therefore a DMA request will likely fail. Checking that a 64KB page is using contiguous MFN is tedious. For now, always says that biovec are not mergeable. 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>
2015-09-08xen: Make clear that swiotlb and biomerge are dealing with DMA addressJulien Grall
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>
2012-01-18xen: using EXPORT_SYMBOL requires including export.hStephen Rothwell
Fix these warnings: drivers/xen/biomerge.c:14:1: warning: data definition has no type or storage class [enabled by default] drivers/xen/biomerge.c:14:1: warning: type defaults to 'int' in declaration of 'EXPORT_SYMBOL' [-Wimplicit-int] drivers/xen/biomerge.c:14:1: warning: parameter names (without types) in function declaration [enabled by default] And this build error: ERROR: "xen_biovec_phys_mergeable" [drivers/block/nvme.ko] undefined! Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-11-04Xen: Export xen_biovec_phys_mergeableMatthew Wilcox
When Xen is enabled, using BIOVEC_PHYS_MERGEABLE in a module causes xen_biovec_phys_mergeable to be referenced, so it needs to be exported. Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
2010-10-18xen: define BIOVEC_PHYS_MERGEABLE()Jeremy Fitzhardinge
Impact: allow Xen control of bio merging When running in Xen domain with device access, we need to make sure the block subsystem doesn't merge requests across pages which aren't machine physically contiguous. To do this, we define our own BIOVEC_PHYS_MERGEABLE. When CONFIG_XEN isn't enabled, or we're not running in a Xen domain, this has identical behaviour to the normal implementation. When running under Xen, we also make sure the underlying machine pages are the same or adjacent. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>