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Date: Sat, 7 Mar 2015 16:38:24 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Dave Hansen <dave.hansen@intel.com>, Borislav Petkov <bp@suse.de>,
        Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Pekka Riikonen <priikone@iki.fi>, Rik van Riel <riel@redhat.com>,
        Suresh Siddha <sbsiddha@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "Yu, Fenghua" <fenghua.yu@intel.com>,
        Quentin Casasnovas <quentin.casasnovas@oracle.com>
Subject: [PATCH 0/1] x86/fpu: x86/fpu: avoid math_state_restore() without
	used_math() in __restore_xstate_sig()
Message-ID: <20150307153824.GA25954@redhat.com>
References: <54F74F59.5070107@intel.com> <20150305195127.GA12657@redhat.com>
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On 03/05, Oleg Nesterov wrote:
>
> The patch is horrible, yes. But simple, and math_state_restore/init_fpu
> are already horrible and need the cleanups.

OK, nobody liked it. How about this one for stable?

Ingo, Linus, Andy. I do agree, math_state_restore() should be called with
irqs enabled. And I was going to do this too. But this is wrong without
other changed. I hope I send them soon.

We need to remove this !tsk_used_math() code from math_state_restore().
And init_fpu() should die. Just look at __restore_xstate_sig() changed
by this patch. Why does it call init_fpu() ? We only need fpu_alloc().
fpu_finit() is pointless, we are going to overwrite fpu->state. used_math()
makes no sense at this point. user_fpu_begin() and math_state_restore()
should set this flag. And other changes.

Could you please review?

Oleg.