Intel IOMMU: Intel IOMMU driver

Actual intel IOMMU driver.  Hardware spec can be found at:
http://www.intel.com/technology/virtualization

This driver sets X86_64 'dma_ops', so hook into standard DMA APIs.  In this
way, PCI driver will get virtual DMA address.  This change is transparent to
PCI drivers.

[akpm@linux-foundation.org: remove unneeded cast]
[akpm@linux-foundation.org: build fix]
[bunk@stusta.de: fix duplicate CONFIG_DMAR Makefile line]
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Muli Ben-Yehuda <muli@il.ibm.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 93 insertions, 0 deletions

diff --git a/Documentation/Intel-IOMMU.txt b/Documentation/Intel-IOMMU.txt
new file mode 100644
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+Linux IOMMU Support
+===================
+
+The architecture spec can be obtained from the below location.
+
+http://www.intel.com/technology/virtualization/
+
+This guide gives a quick cheat sheet for some basic understanding.
+
+Some Keywords
+
+DMAR - DMA remapping
+DRHD - DMA Engine Reporting Structure
+RMRR - Reserved memory Region Reporting Structure
+ZLR  - Zero length reads from PCI devices
+IOVA - IO Virtual address.
+
+Basic stuff
+-----------
+
+ACPI enumerates and lists the different DMA engines in the platform, and
+device scope relationships between PCI devices and which DMA engine  controls
+them.
+
+What is RMRR?
+-------------
+
+There are some devices the BIOS controls, for e.g USB devices to perform
+PS2 emulation. The regions of memory used for these devices are marked
+reserved in the e820 map. When we turn on DMA translation, DMA to those
+regions will fail. Hence BIOS uses RMRR to specify these regions along with
+devices that need to access these regions. OS is expected to setup
+unity mappings for these regions for these devices to access these regions.
+
+How is IOVA generated?
+---------------------
+
+Well behaved drivers call pci_map_*() calls before sending command to device
+that needs to perform DMA. Once DMA is completed and mapping is no longer
+required, device performs a pci_unmap_*() calls to unmap the region.
+
+The Intel IOMMU driver allocates a virtual address per domain. Each PCIE
+device has its own domain (hence protection). Devices under p2p bridges
+share the virtual address with all devices under the p2p bridge due to
+transaction id aliasing for p2p bridges.
+
+IOVA generation is pretty generic. We used the same technique as vmalloc()
+but these are not global address spaces, but separate for each domain.
+Different DMA engines may support different number of domains.
+
+We also allocate gaurd pages with each mapping, so we can attempt to catch
+any overflow that might happen.
+
+
+Graphics Problems?
+------------------
+If you encounter issues with graphics devices, you can try adding
+option intel_iommu=igfx_off to turn off the integrated graphics engine.
+
+Some exceptions to IOVA
+-----------------------
+Interrupt ranges are not address translated, (0xfee00000 - 0xfeefffff).
+The same is true for peer to peer transactions. Hence we reserve the
+address from PCI MMIO ranges so they are not allocated for IOVA addresses.
+
+Boot Message Sample
+-------------------
+
+Something like this gets printed indicating presence of DMAR tables
+in ACPI.
+
+ACPI: DMAR (v001 A M I  OEMDMAR  0x00000001 MSFT 0x00000097) @ 0x000000007f5b5ef0
+
+When DMAR is being processed and initialized by ACPI, prints DMAR locations
+and any RMRR's processed.
+
+ACPI DMAR:Host address width 36
+ACPI DMAR:DRHD (flags: 0x00000000)base: 0x00000000fed90000
+ACPI DMAR:DRHD (flags: 0x00000000)base: 0x00000000fed91000
+ACPI DMAR:DRHD (flags: 0x00000001)base: 0x00000000fed93000
+ACPI DMAR:RMRR base: 0x00000000000ed000 end: 0x00000000000effff
+ACPI DMAR:RMRR base: 0x000000007f600000 end: 0x000000007fffffff
+
+When DMAR is enabled for use, you will notice..
+
+PCI-DMA: Using DMAR IOMMU
+
+TBD
+----
+
+- For compatibility testing, could use unity map domain for all devices, just
+  provide a 1-1 for all useful memory under a single domain for all devices.
+- API for paravirt ops for abstracting functionlity for VMM folks.