Re: [PATCH 1/2] msi: Invert the sense of the MSI enables.

From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Date: Thu, 24 May 2007 21:31:57 -0700

On Thu, 24 May 2007 22:19:09 -0600 ebiederm@xxxxxxxxxxxx (Eric W. Biederman) wrote:

Currently we blacklist known bad msi configurations which means we
keep getting MSI enabled on chipsets that either do not support MSI,
or MSI is implemented improperly. Since the normal IRQ routing
mechanism seems to works even when MSI does not, this is a bad default
and causes non-functioning systems for no good reason.

So this patch inverts the sense of the MSI bus flag to only enable
MSI on known good systems. I am seeding that list with the set of
chipsets with an enabled hypertransport MSI mapping capability. Which
is as close as I can come to an generic MSI enable. So for actually
using MSI this patch is a regression, but for just having MSI enabled
in the kernel by default things should just work with this patch
applied.

People can still enable MSI on a per bus level for testing by writing
to sysfs so discovering chipsets that actually work (assuming we are
using modular drivers) should be pretty straight forward.

Yup.

Do we have a feel for how much performace we're losing on those
systems which _could_ do MSI, but which will end up defaulting
to not using it?
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Follow-Ups:
- Re: [PATCH 1/2] msi: Invert the sense of the MSI enables.
  - From: Andi Kleen
- Re: [PATCH 1/2] msi: Invert the sense of the MSI enables.
  - From: Grant Grundler
- Re: [PATCH 1/2] msi: Invert the sense of the MSI enables.
  - From: Eric W. Biederman

References:
- [PATCH 1/2] msi: Invert the sense of the MSI enables.
  - From: Eric W. Biederman

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Relevant Pages

[PATCH]2.6.3-rc2 MSI Documentation
... After getting feedback from Tom,I made some changes to the patch ... -configuration option must be selected to enable MSI/MSI-X support. ... Including MSI support into the kernel ... -setting CONFIG_PCI_USE_VECTOR enables the VECTOR based scheme and ...
(Linux-Kernel)
RE: KB928365 Err 663, on production SQL2K5 serve CANNOT uninstall
... version of the patch that includes whatever content might ... another Win2003 server, copy it to your affected server ... compared with another server and there is much more msi and even msp files, ...
(microsoft.public.windowsupdate)
RE: Sharepoint, monitoring and the company web
... MSI: Executing op: ... MSI: File will have security applied from OpCode. ... installed; No patch; No existing file ...
(microsoft.public.windows.server.sbs)
Re: [PATCH 9/21] MSI: Expand pci_msi_supported()
... Can we please change the return value here so it is actually boolean. ... My next patch allows the arch routine to propagate its return value out ... to the caller, which is useful. ... If MSI is supported we return 0. ...
(Linux-Kernel)
[PATCH 0/8] Improve MSI detection v2
... After my proposal to whitelist chipsets supporting MSI a couple days ago, ... We enable MSI by default on PCI-E and disable on non-PCI-E chipsets. ... #3 - Blacklist PCI-E chipsets depending on Hypertransport MSI capabality ...
(Linux-Kernel)