linux-kernel - Re: ABI change for device drivers using future AVX instruction set

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Message-ID: <486780BA.6010202@qumranet.com>
Date:	Sun, 29 Jun 2008 15:31:54 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Agner Fog <agner@...er.org>,
	Arjan van de Ven <arjan@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: ABI change for device drivers using future AVX instruction set

Andi Kleen wrote:
> Avi Kivity wrote:
>
>   
>> This is fixable. 
>>     
>
> Sure nearly everything is fixable, but why would you want to do that?
>
> For me the best fix currently seems to be to just not do that
> when it hurts.
>
>   

We already use sse in the kernel (raid), presumably disabling preemption 
there hurts some workloads.

With sse/avx gaining more features, we may see more requirements for 
kernel fpu.

>> We could change kernel_fpu_begin() not to disable
>> preemption, but instead set a task flag.  When we get the "no device"
>> fault, if the flag is set, save the fpu state into the kernel fpu save
>> area 
>>     
>
> What kernel fpu save area do you mean?
>   

A new one, of course.

-- 
error compiling committee.c: too many arguments to function

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