linux-kernel - Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues

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Message-ID: <5723C5FC.5090302@linux.intel.com>
Date:	Fri, 29 Apr 2016 13:37:16 -0700
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:	x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH v4 0/10] x86/xsaves: Fix XSAVES known issues

On 04/29/2016 01:07 PM, Yu-cheng Yu wrote:
> On Fri, Apr 29, 2016 at 01:03:43PM -0700, Dave Hansen wrote:
>>> That's not feasible.  Think of dynamic libraries or just-in-time 
>>> compilers.  What instruction set does /usr/bin/java use, for
>>> instance? :)
> The java argument is true. In that case or when the bitmask is
> missing, we can allocate for all supported features.

Remember, execve() doesn't replace the task_struct.  How do we resize
the task_struct at execve() time?  If /bin/bash doesn't use AVX, then
fork()s and execve()s an AVX-using program, what do we do?