diff options
| author | Leann Ogasawara <leann.ogasawara@canonical.com> | 2011-09-07 13:56:47 -0700 |
|---|---|---|
| committer | John Rigby <john.rigby@linaro.org> | 2011-10-17 09:56:49 -0600 |
| commit | db43299cc4f506ee41b1863b7f250b99bd6dc985 (patch) | |
| tree | c7fcaaeb4e68bbbe7640f49d04e9a4e2ed01de6c /Documentation | |
| parent | 3c72b97c6315f9828b1809627718008b26031178 (diff) | |
UBUNTU: SAUCE: (drop after 3.0) x86, x2apic: enable the bios request for x2apic optout
BugLink: http://bugs.launchpad.net/bugs/797548
On the platforms which are x2apic and interrupt-remapping capable, Linux
kernel is enabling x2apic even if the BIOS doesn't. This is to take
advantage of the features that x2apic brings in.
Some of the OEM platforms are running into issues because of this, as their
bios is not x2apic aware. For example, this was resulting in interrupt migration
issues on one of the platforms. Also if the BIOS SMI handling uses APIC
interface to send SMI's, then the BIOS need to be aware of x2apic mode
that OS has enabled.
On some of these platforms, BIOS doesn't have a HW mechanism to turnoff
the x2apic feature to prevent OS from enabling it.
To resolve this mess, recent changes to the VT-d2 specification
(http://download.intel.com/technology/computing/vptech/Intel(r)_VT_for_Direct_IO.pdf)
includes a mechanism that provides BIOS a way to request system software
to opt out of enabling x2apic mode.
Look at the x2apic optout flag in the DMAR tables before enabling the x2apic
mode in the platform. Also print a warning that we have disabled x2apic
based on the BIOS request.
Kernel boot parameter "intremap=no_x2apic_optout" can be used to override
the BIOS x2apic optout request.
Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/kernel-parameters.txt | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index f2d382417c6..670694f43bd 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1007,10 +1007,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. has the capability. With this option, super page will not be supported. intremap= [X86-64, Intel-IOMMU] - Format: { on (default) | off | nosid } on enable Interrupt Remapping (default) off disable Interrupt Remapping nosid disable Source ID checking + no_x2apic_optout + BIOS x2APIC opt-out request will be ignored inttest= [IA64] |