Re: iommu: it could use some documentation

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Next thread: Document memmap option better by Pavel Machek on Wednesday, March 19, 2008 - 10:24 am. (1 message)
To: Ingo Molnar <mingo@...>, kernel list <linux-kernel@...>, <andi@...>
Date: Wednesday, March 19, 2008 - 10:58 am

Fix coding style in pci-dma_64.c and add stubs for documentation. I
hope someone fills the rest, I understand maybe off and soft...

Signed-off-by: Pavel Machek <pavel@suse.cz>

---
commit 3ab83390752b5e71c6f04230dcd25c7789bb5099
tree 295a3567278a216785cd4e32dc3bcae2c5aad572
parent d5ac3c822e1036165b92d62e464be1e61c12d757
author Pavel <pavel@amd.ucw.cz> Wed, 19 Mar 2008 15:57:03 +0100
committer Pavel <pavel@amd.ucw.cz> Wed, 19 Mar 2008 15:57:03 +0100

Documentation/kernel-parameters.txt | 13 +++++++++++++
arch/x86/kernel/pci-dma_64.c | 20 ++++++++++----------
2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 467034c..d803f70 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -811,6 +811,19 @@ and is between 256 and 4096 characters.

inttest= [IA64]

+ iommu= [x86]
+ off
+ force
+ noforce
+ biomerge
+ panic
+ nopanic
+ merge
+ nomerge
+ forcesac
+ soft
+
+
intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
off
Disable intel iommu driver.
diff --git a/arch/x86/kernel/pci-dma_64.c b/arch/x86/kernel/pci-dma_64.c
index a82473d..a9d3f54 100644
--- a/arch/x86/kernel/pci-dma_64.c
+++ b/arch/x86/kernel/pci-dma_64.c
@@ -237,32 +237,32 @@ static __init int iommu_setup(char *p)
return -EINVAL;

while (*p) {
- if (!strncmp(p,"off",3))
+ if (!strncmp(p, "off", 3))
no_iommu = 1;
/* gart_parse_options has more force support */
- if (!strncmp(p,"force",5))
+ if (!strncmp(p, "force", 5))
force_iommu = 1;
- if (!strncmp(p,"noforce",7)) {
+ if (!strncmp(p, "noforce", 7)) {
iommu_merge = 0;
force_iommu = 0;
}

- if (!strncmp(p, "biomerge",8)) {
+ if (!strncmp(p, "biomerge", 8)) {
iommu_bio_merge = 4096;
iommu_merge = 1;
force_iommu = 1;
}
- if (!strncmp(p, "panic",5))
+ if (!strncmp(p, "panic", 5))
panic_on_overfl...

To: Pavel Machek <pavel@...>
Cc: Ingo Molnar <mingo@...>, kernel list <linux-kernel@...>
Date: Friday, March 21, 2008 - 11:53 am

The boot options are all documented in
Documentation/x86_64/boot-options.txt, like all other x86-64 specific
boot options.

-Andi
--

To: Pavel Machek <pavel@...>
Cc: kernel list <linux-kernel@...>, <andi@...>, Thomas Gleixner <tglx@...>, H. Peter Anvin <hpa@...>
Date: Wednesday, March 19, 2008 - 11:13 am

these are mostly quirks to get boards booting - few people use these for
performance tuning. SAC has an address space limit (40 bits) but is
faster, DAC can cover the physical address range but is slower. The
softiotlb we better forget about ;-)

if you are interested in fixing this, the descriptions from
Documentation/x86_64/boot-options.txt should/could be merged into
Documentation/kernel-parameters.txt.

Ingo
--

To: Ingo Molnar <mingo@...>
Cc: Pavel Machek <pavel@...>, kernel list <linux-kernel@...>, Thomas Gleixner <tglx@...>, H. Peter Anvin <hpa@...>
Date: Friday, March 21, 2008 - 11:55 am

Actually no. Except perhaps for iommu=soft none of them is related
to any hardware issues. They all tune various performance trade offs
and were supplied for performance tuning originally.

-Andi
--

To: Pavel Machek <pavel@...>
Cc: kernel list <linux-kernel@...>, <andi@...>
Date: Wednesday, March 19, 2008 - 11:06 am

thanks Pavel, i've applied your bits. This file could need a ton more
cleanups.

Ingo
--

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