Messages in this thread | | | From | Konrad Rzeszutek Wilk <> | Subject | [PATCH] Xen-SWIOTBL v0.8.3 used for Xen PCI pass through for PV guests. | Date | Tue, 22 Jun 2010 15:42:33 -0400 |
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These nineteen patches lay the groundwork for Xen Paravirtualized (PV) domains to access PCI pass-through devices. These patches utilize the SWIOTLB library modifications (http://lkml.org/lkml/2010/6/4/272).
The end user of this is the Xen PCI frontend and Xen PCI [1] which require a DMA API "backend" that understands Xen's MMU. This allows the PV domains to use PCI devices.
This patch-set is split in two groups. The first alter the Xen components, while the second introduces the SWIOTLB-Xen.
The Xen components patches consist of:
[PATCH 01/19] xen: use _PAGE_IOMAP in ioremap to do machine mappings [PATCH 02/19] xen: Allow unprivileged Xen domains to create iomap pages [PATCH 03/19] xen: Rename the balloon lock [PATCH 04/19] xen: Add xen_create_contiguous_region
which alter the Xen MMU, which by default utilizes a layer of indirection wherein the PFN is translated to the Machine Frame Number (MFN) and vice-versa. This is required to "fool" the guest in thinking its memory starts at PFN 0 and goes up to the available amount. While in the background, PFN 0 might as well be MFN 1048576 (4GB).
For PCI/DMA API calls (ioremap, pci_map_page, etc) having a PFN != MFN is not too good, so two new mechanisms are introduced: a). For PTEs which manipulate the PCI/DMA pages the PFN == MFN. This is done via utilizing the _PAGE_IOMAP flag to distinguish the PTE as an IO type. b). Allow a mechanism to "swizzle" the MFN's under a PFN to be under a certain bus width (say 32). This allows us to provide a mechanism for the SWIOTLB Xen to allocate memory for its pool that will be guaranteed to be under the 4GB mark.
The SWIOTLB-Xen adds a library that is only used if the machine is detected to be running under Xen. It utilizes the SWIOTLB library bookkeeping functions (swiotlb_tbl_*) and only deals with the virtual to [physical, bus] (and vice-versa) address translations.
The diffstat:
arch/x86/include/asm/xen/page.h | 8 +- arch/x86/include/asm/xen/swiotlb-xen.h | 14 + arch/x86/kernel/pci-dma.c | 7 +- arch/x86/xen/Kconfig | 4 + arch/x86/xen/Makefile | 1 + arch/x86/xen/enlighten.c | 4 + arch/x86/xen/mmu.c | 291 ++++++++++++++++++- arch/x86/xen/pci-swiotlb-xen.c | 58 ++++ drivers/xen/balloon.c | 15 +- include/linux/swiotlb-xen.h | 65 ++++ include/xen/interface/memory.h | 50 +++ include/xen/xen-ops.h | 6 + lib/Makefile | 1 + lib/swiotlb-xen.c | 515 ++++++++++++++++++++++++++++++++ 14 files changed, 1018 insertions(+), 21 deletions(-)
[1]: The Xen PCI and Xen PCI fronted patches, which have not yet been posted are available at git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git under the branch devel/xen-pcifront-0.2. A merge of all required branches is under 'devel/merge.2.6.35-rc3'. Or 'devel/merge.2.6.34'. I will post them quite soon.
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