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Date: Tue, 24 Apr 2007 23:17:55 +0200 From: "Markus Rechberger" <mrechberger@...il.com> To: "Ashok Raj" <ashok.raj@...el.com> Cc: linux-kernel@...r.kernel.org, akpm@...l.org, ak@...e.de, gregkh@...e.de, muli@...ibm.com, asit.k.mallick@...el.com, suresh.b.siddha@...el.com, anil.s.keshavamurthy@...el.com, arjan@...ux.intel.com, shaohua.li@...el.com Subject: Re: [Intel IOMMU][patch 6/8] Doc updates for Intel Virtualization Technology for Directed I/O. On 4/23/07, Ashok Raj <ashok.raj@...el.com> wrote: > Document Intel IOMMU driver boot option. > > Signed-off-by: Ashok Raj <ashok.raj@...el.com> > Signed-off-by: Shaohua Li <shaohua.li@...el.com> > Index: linux-2.6.21-rc5/Documentation/Intel-IOMMU.txt > =================================================================== > --- /dev/null 1970-01-01 00:00:00.000000000 +0000 > +++ linux-2.6.21-rc5/Documentation/Intel-IOMMU.txt 2007-04-17 > 05:41:56.000000000 -0700 > @@ -0,0 +1,119 @@ > +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. > + guess you probably mean guard tables here... Markus > + > +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. > + > +If it happens to be a PCI device included in the INCLUDE_ALL Engine, > +then try the intel_iommu=gfx_workaround to setup a 1-1 map. We hear > +graphics drivers may be in process of using DMA api's in the near > +future.... > + > +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. > + > + > +Fault reporting > +--------------- > +When errors are reported, the DMA engine signals via an interrupt. The > fault > +reason and device that caused it with fault reason is printed on console. > + > +See below for sample. > + > + > +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 > + > +Fault reporting > +--------------- > + > +DMAR:[DMA Write] Request device [00:02.0] fault addr 6df084000 > +DMAR:[fault reason 05] PTE Write access is not set > +DMAR:[DMA Write] Request device [00:02.0] fault addr 6df084000 > +DMAR:[fault reason 05] PTE Write access is not set > + > +TBD > +---- > + > +- No Performance tuning / analysis yet. > +- sysfs needs useful data to be populated. > + DMAR info, device scope, stats could be exposed to some extent. > +- Add support to Firmware Developer Kit to test ACPI tables for DMAR. > +- 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. > Index: linux-2.6.21-rc5/Documentation/kernel-parameters.txt > =================================================================== > --- linux-2.6.21-rc5.orig/Documentation/kernel-parameters.txt 2007-04-17 > 04:59:42.000000000 -0700 > +++ linux-2.6.21-rc5/Documentation/kernel-parameters.txt 2007-04-17 > 05:41:56.000000000 -0700 > @@ -710,6 +710,26 @@ > > inttest= [IA64] > > + intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option > + off > + Disable intel iommu driver. > + forcerw > + Some drivers might incorrectly map DMA buffers as > + write-only even when the device, requires read/write > + mapping. This option works around the issue in IOMMU > + driver by making all write-only map as read/write. > + Default is off. > + igfx_off [Default Off] > + By default, gfx is mapped as normal device. If a gfx > + device has a dedicated DMAR unit, the DMAR unit is > + bypassed with this option. In this case, gfx device > + will use physical address for DMA. > + gfx_workaround [Default Off] > + gfx devices tend to use physical address for DMA and > + avoid using DMA api's. Setting this option permits > + the IOMMU driver to set a unity map for all OS > + visible memory. Hence the driver can continue to use > + physical addresses for DMA. > io7= [HW] IO7 for Marvel based alpha systems > See comment before marvel_specify_io7 in > arch/alpha/kernel/core_marvel.c. > > -- > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Markus Rechberger - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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