Commit Graph

37 Commits

Author SHA1 Message Date
Suresh Siddha
fa4b57cc04 x86, dmar: use atomic allocations for QI and Intr-remapping init
Impact: invalid use of GFP_KERNEL in interrupt context

Queued invalidation and interrupt-remapping will get initialized with
interrupts disabled (while enabling interrupt-remapping). So use
GFP_ATOMIC instead of GFP_KERNEL for memory alloacations.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2009-03-17 16:49:30 -07:00
Suresh Siddha
1531a6a6b8 x86, dmar: start with sane state while enabling dma and interrupt-remapping
Impact: cleanup/sanitization

Start from a sane state while enabling dma and interrupt-remapping, by
clearing the previous recorded faults and disabling previously
enabled queued invalidation and interrupt-remapping.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2009-03-17 15:39:58 -07:00
Suresh Siddha
eba67e5da6 x86, dmar: routines for disabling queued invalidation and intr remapping
Impact: new interfaces (not yet used)

Routines for disabling queued invalidation and interrupt remapping.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2009-03-17 15:39:20 -07:00
Suresh Siddha
9d783ba042 x86, x2apic: enable fault handling for intr-remapping
Impact: interface augmentation (not yet used)

Enable fault handling flow for intr-remapping aswell. Fault handling
code now shared by both dma-remapping and intr-remapping.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2009-03-17 15:38:59 -07:00
Suresh Siddha
0ac2491f57 x86, dmar: move page fault handling code to dmar.c
Impact: code movement

Move page fault handling code to dmar.c
This will be shared both by DMA-remapping and Intr-remapping code.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2009-03-17 15:37:06 -07:00
Ingo Molnar
55f2b78995 Merge branch 'x86/urgent' into x86/pat 2009-03-01 12:47:58 +01:00
Tony Battersby
084eb960e8 intel-iommu: fix endless "Unknown DMAR structure type" loop
I have a SuperMicro C2SBX motherboard with BIOS revision 1.0b.  With vt-d
enabled in the BIOS, Linux gets into an endless loop printing
"DMAR:Unknown DMAR structure type" when booting.  Here is the DMAR ACPI
table:

DMAR @ 0x7fe86dec
  0000: 44 4d 41 52 98 00 00 00 01 6f 49 6e 74 65 6c 20  DMAR.....oIntel
  0010: 4f 45 4d 44 4d 41 52 20 00 00 04 06 4c 4f 48 52  OEMDMAR ....LOHR
  0020: 01 00 00 00 23 00 00 00 00 00 00 00 00 00 00 00  ....#...........
  0030: 01 00 58 00 00 00 00 00 00 a0 e8 7f 00 00 00 00  ..X.............
  0040: ff ff ef 7f 00 00 00 00 01 08 00 00 00 00 1d 00  ................
  0050: 01 08 00 00 00 00 1d 01 01 08 00 00 00 00 1d 02  ................
  0060: 01 08 00 00 00 00 1d 07 01 08 00 00 00 00 1a 00  ................
  0070: 01 08 00 00 00 00 1a 01 01 08 00 00 00 00 1a 02  ................
  0080: 01 08 00 00 00 00 1a 07 01 08 00 00 00 00 1a 07  ................
  0090: c0 00 68 00 04 10 66 60                          ..h...f`

Here are the messages printed by the kernel:

DMAR:Host address width 36
DMAR:RMRR base: 0x000000007fe8a000 end: 0x000000007fefffff
DMAR:Unknown DMAR structure type
DMAR:Unknown DMAR structure type
DMAR:Unknown DMAR structure type
...

Although I not very familiar with ACPI, to me it looks like struct
acpi_dmar_header::length == 0x0058 is incorrect, causing
parse_dmar_table() to look at an invalid offset on the next loop.  This
offset happens to have struct acpi_dmar_header::length == 0x0000, which
prevents the loop from ever terminating.  This patch checks for this
condition and bails out instead of looping forever.

Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2009-02-14 08:33:34 +00:00
Yinghai Lu
8e1568f350 pci, x86, acpi: fix early_ioremap() leak
Pawel reported:
------------[ cut here ]------------
WARNING: at arch/x86/mm/ioremap.c:616 check_early_ioremap_leak+0x52/0x67()
Hardware name:
Debug warning: early ioremap leak of 1 areas detected.
Modules linked in:
Pid: 1, comm: swapper Not tainted 2.6.29-rc4-tip #2
...

Reported-by: Pawel Dziekonski <dzieko@gmail.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-11 14:20:10 +01:00
Yu Zhao
704126ad81 VT-d: handle Invalidation Queue Error to avoid system hang
When hardware detects any error with a descriptor from the invalidation
queue, it stops fetching new descriptors from the queue until software
clears the Invalidation Queue Error bit in the Fault Status register.
Following fix handles the IQE so the kernel won't be trapped in an
infinite loop.

Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2009-02-09 11:03:17 +00:00
Joerg Roedel
43f7392ba9 intel-iommu: fix build error with INTR_REMAP=y and DMAR=n
This fix should be safe since iommu->agaw is only used in intel-iommu.c.
And this file is only compiled with DMAR=y.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2009-02-09 10:00:53 +00:00
Weidong Han
1b5736839a calculate agaw for each iommu
"SAGAW" capability may be different across iommus. Use a default agaw, but if default agaw is not supported in some iommus, choose a less supported agaw.

Signed-off-by: Weidong Han <weidong.han@intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
2009-01-03 14:02:18 +01:00
Yu Zhao
2e824f7924 VT-d: fix segment number being ignored when searching DRHD
On platforms with multiple PCI segments, any of the segments can have a DRHD
with INCLUDE_PCI_ALL flag. So need to check the DRHD's segment number against
the PCI device's when searching its DRHD.

Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
2009-01-03 12:05:28 +01:00
David Woodhouse
b876d08f81 Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6
Conflicts:

	drivers/pci/dmar.c
2008-10-21 19:42:20 +01:00
Linus Torvalds
9301975ec2 Merge branch 'genirq-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
This merges branches irq/genirq, irq/sparseirq-v4, timers/hpet-percpu
and x86/uv.

The sparseirq branch is just preliminary groundwork: no sparse IRQs are
actually implemented by this tree anymore - just the new APIs are added
while keeping the old way intact as well (the new APIs map 1:1 to
irq_desc[]).  The 'real' sparse IRQ support will then be a relatively
small patch ontop of this - with a v2.6.29 merge target.

* 'genirq-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (178 commits)
  genirq: improve include files
  intr_remapping: fix typo
  io_apic: make irq_mis_count available on 64-bit too
  genirq: fix name space collisions of nr_irqs in arch/*
  genirq: fix name space collision of nr_irqs in autoprobe.c
  genirq: use iterators for irq_desc loops
  proc: fixup irq iterator
  genirq: add reverse iterator for irq_desc
  x86: move ack_bad_irq() to irq.c
  x86: unify show_interrupts() and proc helpers
  x86: cleanup show_interrupts
  genirq: cleanup the sparseirq modifications
  genirq: remove artifacts from sparseirq removal
  genirq: revert dynarray
  genirq: remove irq_to_desc_alloc
  genirq: remove sparse irq code
  genirq: use inline function for irq_to_desc
  genirq: consolidate nr_irqs and for_each_irq_desc()
  x86: remove sparse irq from Kconfig
  genirq: define nr_irqs for architectures with GENERIC_HARDIRQS=n
  ...
2008-10-20 13:23:01 -07:00
David Woodhouse
f82851a8a4 dmar: fix uninitialised 'ret' variable in dmar_parse_dev()
This was introduced by commit 1886e8a90a
("x64, x2apic/intr-remap: code re-structuring, to be used by both DMA
and Interrupt remapping"). It was causing bogus results to be returned
from dmar_parse_dev() when the first unit with the INCLUDE_ALL flag was
processed.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2008-10-18 15:45:48 +01:00
Fenghua Yu
5b6985ce8e intel-iommu: IA64 support
The current Intel IOMMU code assumes that both host page size and Intel
IOMMU page size are 4KiB. The first patch supports variable page size.
This provides support for IA64 which has multiple page sizes.

This patch also adds some other code hooks for IA64 platform including
DMAR_OPERATION_TIMEOUT definition.

[dwmw2: some cleanup]
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2008-10-18 14:29:15 +01:00
Youquan Song
cacd4213d8 dmar: remove the quirk which disables dma-remapping when intr-remapping enabled
Now that we have DMA-remapping support for queued invalidation, we
can enable both DMA-remapping and interrupt-remapping at the same time.

Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2008-10-17 08:05:30 +01:00
Youquan Song
3481f21097 dmar: context cache and IOTLB invalidation using queued invalidation
Implement context cache invalidate and IOTLB invalidation using
queued invalidation interface. This interface will be used by
DMA remapping, when queued invalidation is supported.

Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2008-10-17 08:03:14 +01:00
Suresh Siddha
f05810c996 dmar: use spin_lock_irqsave() in qi_submit_sync()
Next patch in the series will use queued invalidation interface
qi_submit_sync() for DMA-remapping aswell, which can be called from interrupt
context.

So use spin_lock_irqsave() instead of spin_lock() in qi_submit_sync().

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2008-10-17 08:03:05 +01:00
Suresh Siddha
1c7d1bcad2 dmar: fix dmar_parse_dev() devices_cnt error condition check
It is possible that,
instead of PCI endpoint/sub-hierarchy structures, only IO-APIC/HPET
devices may be reported under device scope structures. Fix the devices_cnt
error check, which cares about only PCI structures and removes the
dma-remapping unit structure (dmaru) when the devices_cnt is zero
and include_all flag is not set.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-16 16:53:05 +02:00
Suresh Siddha
04e2ea6706 dmar: use list_for_each_entry_safe() in dmar_dev_scope_init()
In dmar_dev_scope_init(), functions called under for_each_drhd_unit()/
for_each_rmrr_units() can delete the list entry under some error conditions.

So we should use list_for_each_entry_safe() for safe traversal.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-16 16:53:05 +02:00
Yinghai Lu
74d04bd7dc dmar: initialize the return value in dmar_parse_dev()
initialize the return value in dmar_parse_dev()

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-16 16:53:05 +02:00
Yinghai Lu
f6dd5c3106 dmar: fix using early fixmap mapping for DMAR table parsing
Very early detection of the DMAR tables will setup fixmap mapping. For
parsing these tables later (while enabling dma and/or interrupt remapping),
early fixmap mapping shouldn't be used. Fix it by calling table detection
routines again, which will call generic apci_get_table() for setting up
the correct mapping.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-16 16:53:04 +02:00
Kay, Allen M
3871794642 VT-d: Changes to support KVM
This patch extends the VT-d driver to support KVM

[Ben: fixed memory pinning]
[avi: move dma_remapping.h as well]

Signed-off-by: Kay, Allen M <allen.m.kay@intel.com>
Signed-off-by: Weidong Han <weidong.han@intel.com>
Signed-off-by: Ben-Ami Yassour <benami@il.ibm.com>
Signed-off-by: Amit Shah <amit.shah@qumranet.com>
Acked-by: Mark Gross <mgross@linux.intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-10-15 14:24:08 +02:00
Suresh Siddha
1cb11583a6 x64, x2apic/intr-remap: disable DMA-remapping if Interrupt-remapping is detected (temporary quirk)
Interrupt-remapping enables queued invalidation. And once queued invalidation
is enabled, IOTLB invalidation also needs to use the queued invalidation
mechanism and the register based IOTLB invalidation doesn't work.

For now, Support for IOTLB invalidation using queued invalidation is
missing. Meanwhile, disable DMA-remapping, if Interrupt-remapping
support is detected.

For the meanwhile, if someone wants to really enable DMA-remapping, they
can use nox2apic, which will disable interrupt-remapping and as such
doesn't enable queued invalidation.

And given that none of the release platforms support intr-remapping yet,
we should be ok for this temporary hack.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-12 08:45:00 +02:00
Suresh Siddha
2ae2101069 x64, x2apic/intr-remap: Interrupt remapping infrastructure
Interrupt remapping (part of Intel Virtualization Tech for directed I/O)
infrastructure.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-12 08:44:53 +02:00
Suresh Siddha
fe962e90cb x64, x2apic/intr-remap: Queued invalidation infrastructure (part of VT-d)
Queued invalidation (part of Intel Virtualization Technology for
Directed I/O architecture) infrastructure.

This will be used for invalidating the interrupt entry cache in the
case of Interrupt-remapping and IOTLB invalidation in the case
of DMA-remapping.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-12 08:44:52 +02:00
Suresh Siddha
ad3ad3f6a2 x64, x2apic/intr-remap: parse ioapic scope under vt-d structures
Parse the vt-d device scope structures to find the mapping between IO-APICs
and the interrupt remapping hardware units.

This will be used later for enabling Interrupt-remapping for IOAPIC devices.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-12 08:44:50 +02:00
Suresh Siddha
2d6b5f85bb x64, x2apic/intr-remap: Fix the need for RMRR in the DMA-remapping detection
Presence of RMRR structures is not compulsory for enabling DMA-remapping.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Yong Y Wang <yong.y.wang@intel.com>
Cc: Yong Y Wang <yong.y.wang@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-12 08:44:50 +02:00
Suresh Siddha
aaa9d1dd63 x64, x2apic/intr-remap: use CONFIG_DMAR for DMA-remapping specific code
DMA remapping specific code covered with CONFIG_DMAR in
the generic code which will also be used later for enabling Interrupt-remapping.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-12 08:44:49 +02:00
Suresh Siddha
1886e8a90a x64, x2apic/intr-remap: code re-structuring, to be used by both DMA and Interrupt remapping
Allocate the iommu during the parse of DMA remapping hardware
definition structures. And also, introduce routines for device
scope initialization which will be explicitly called during
dma-remapping initialization.

These will be used for enabling interrupt remapping separately from the
existing DMA-remapping enabling sequence.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-12 08:44:48 +02:00
Suresh Siddha
c42d9f3244 x64, x2apic/intr-remap: fix the need for sequential array allocation of iommus
Clean up the intel-iommu code related to deferred iommu flush logic. There is
no need to allocate all the iommu's as a sequential array.

This will be used later in the interrupt-remapping patch series to
allocate iommu much early and individually for each device remapping
hardware unit.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-12 08:44:47 +02:00
Suresh Siddha
e61d98d8da x64, x2apic/intr-remap: Intel vt-d, IOMMU code reorganization
code reorganization of the generic Intel vt-d parsing related routines and linux
iommu routines specific to Intel vt-d.

drivers/pci/dmar.c	now contains the generic vt-d parsing related routines
drivers/pci/intel_iommu.c contains the iommu routines specific to vt-d

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-12 08:44:46 +02:00
mark gross
98bcef56ca copyright owner and author clean up for intel iommu and related files
The following is a clean up and correction of the copyright holding
entities for the files associated with the intel iommu code.

Signed-off-by: <mgross@linux.intel.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-23 17:12:14 -08:00
David Miller
f661197e0a Genericizing iova.[ch]
I would like to potentially move the sparc64 IOMMU code over to using
the nice new drivers/pci/iova.[ch] code for free area management..

In order to do that we have to detach the IOMMU page size assumptions
which only really need to exist in the intel-iommu.[ch] code.

This patch attempts to implement that.

[akpm@linux-foundation.org: build fix]
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-06 10:41:01 -08:00
Fenghua Yu
093f87d279 PCI: More Sanity checks for DMAR
Add and changes a few sanity checks in dmar.c.

1.  The haw field in ACPI DMAR table in VT-d spec doesn't describe the
   range of haw.  But since DMA page size is 4KB in DMA remapping, haw
   should be at least 4KB.  The current VT-d code in dmar.c returns failure
   when haw==0.  This sanity check is not accurate and execution can pass
   when haw is less than one page size 4KB.  This patch changes the haw
   sanity check to validate if haw is less than 4KB.

2. Add dmar_rmrr_units verification.

3. Add parse_dmar_table() verification.

[akpm@linux-foundation.org: coding-style fixes]

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Acked-by: mark gross <mgross@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2008-02-01 15:04:21 -08:00
Keshavamurthy, Anil S
10e5247f40 Intel IOMMU: DMAR detection and parsing logic
This patch supports the upcomming Intel IOMMU hardware a.k.a.  Intel(R)
Virtualization Technology for Directed I/O Architecture and the hardware spec
for the same can be found here
http://www.intel.com/technology/virtualization/index.htm

FAQ! (questions from akpm, answers from ak)

> So...  what's all this code for?
>
> I assume that the intent here is to speed things up under Xen, etc?

Yes in some cases, but not this code.  That would be the Xen version of this
code that could potentially assign whole devices to guests.  I expect this to
be only useful in some special cases though because most hardware is not
virtualizable and you typically want an own instance for each guest.

Ok at some point KVM might implement this too; i likely would use this code
for this.

> Do we
> have any benchmark results to help us to decide whether a merge would be
> justified?

The main advantage for doing it in the normal kernel is not performance, but
more safety.  Broken devices won't be able to corrupt memory by doing random
DMA.

Unfortunately that doesn't work for graphics yet, for that need user space
interfaces for the X server are needed.

There are some potential performance benefits too:

- When you have a device that cannot address the complete address range an
  IOMMU can remap its memory instead of bounce buffering.  Remapping is likely
  cheaper than copying.

- The IOMMU can merge sg lists into a single virtual block.  This could
  potentially speed up SG IO when the device is slow walking SG lists.  [I
  long ago benchmarked 5% on some block benchmark with an old MPT Fusion; but
  it probably depends a lot on the HBA]

And you get better driver debugging because unexpected memory accesses from
the devices will cause a trappable event.

>
> Does it slow anything down?

It adds more overhead to each IO so yes.

This patch:

Add support for early detection and parsing of DMAR's (DMA Remapping) reported
to OS via ACPI tables.

DMA remapping(DMAR) devices support enables independent address translations
for Direct Memory Access(DMA) from Devices.  These DMA remapping devices are
reported via ACPI tables and includes pci device scope covered by these DMA
remapping device.

For detailed info on the specification of "Intel(R) Virtualization Technology
for Directed I/O Architecture" please see
http://www.intel.com/technology/virtualization/index.htm

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>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-22 08:13:18 -07:00