linux-kernel - Re: [patch 1/2] x86, fpu: split FPU state from task struct

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Date:	Tue, 11 Mar 2008 13:09:22 +0300
From:	"Alexey Dobriyan" <adobriyan@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Suresh Siddha" <suresh.b.siddha@...el.com>, hpa@...or.com,
	tglx@...utronix.de, andi@...stfloor.org, hch@...radead.org,
	linux-kernel@...r.kernel.org,
	"Arjan van de Ven" <arjan@...ux.intel.com>
Subject: Re: [patch 1/2] x86, fpu: split FPU state from task struct - v5

On 3/11/08, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Alexey Dobriyan <adobriyan@...il.com> wrote:
>
> > > -	extern void __bad_fxsave_alignment(void);
> > > -
> > > -	if (offsetof(struct task_struct, thread.i387.fxsave) & 15)
> > > -	__bad_fxsave_alignment();
> >
> > I think removal of such checks needs giving necessary alignment to
> > cache. Previously it worked because of __aligned((16)) and
> > L1_CACHE_SHIFT combo.
>
> it's still checked, just elsewhere:
>
> > + WARN_ON((unsigned long)dst->thread.xstate & 15);
>
> i'd not expect us to ever align worse than 16 bytes in the future

But sysfs tells me alignment of "xstate" is 8 now. Object size is 512 which
is masking it.
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