Re: [PATCH] Set bit 1 in disabled processor's _STA

[Avi Kivity <avi@redhat.com>]

Gleb Natapov wrote:
> On Sun, May 17, 2009 at 11:07:31PM +0300, Avi Kivity wrote:
>   
>> Gleb Natapov wrote:
>>     
>>> Theoretically we can provide different values for different OSes, but
>>> this is just a guess work since there is no any documentation how CPU
>>> hot-plug should work on x86.
>>>   
>>>       
>> ACPI in fact supports this, but I hope we don't have to do that.
>>
>>     
> ACPI way is what I am talking about. Implement _OS object.
>   

/*
 * The story of _OSI(Linux)
 *
 * From pre-history through Linux-2.6.22,
 * Linux responded TRUE upon a BIOS OSI(Linux) query.
 *
 * Unfortunately, reference BIOS writers got wind of this
 * and put OSI(Linux) in their example code, quickly exposing
 * this string as ill-conceived and opening the door to
 * an un-bounded number of BIOS incompatibilities.
 *
 * For example, OSI(Linux) was used on resume to re-POST a
 * video card on one system, because Linux at that time
 * could not do a speedy restore in its native driver.
 * But then upon gaining quick native restore capability,
 * Linux has no way to tell the BIOS to skip the time-consuming
 * POST -- putting Linux at a permanent performance disadvantage.
 * On another system, the BIOS writer used OSI(Linux)
 * to infer native OS support for IPMI!  On other systems,
 * OSI(Linux) simply got in the way of Linux claiming to
 * be compatible with other operating systems, exposing
 * BIOS issues such as skipped device initialization.
 *
 * So "Linux" turned out to be a really poor chose of
 * OSI string, and from Linux-2.6.23 onward we respond FALSE.
 *
 * BIOS writers should NOT query _OSI(Linux) on future systems.
 * Linux will complain on the console when it sees it, and return FALSE.
 * To get Linux to return TRUE for your system  will require
 * a kernel source update to add a DMI entry,
 * or boot with "acpi_osi=Linux"
 */

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-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.