Re: [PATCH 02/19] x86, fpu: Wrap get_xsave_addr() to make it safer

[Thomas Gleixner <tglx@linutronix.de>]

On Mon, 18 May 2015, Dave Hansen wrote:
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> The MPX code appears to be saving off the FPU in an unsafe
> way.  It does not disable preemption or ensure that the
> FPU state has been allocated.  All of the preemption safety
> comes from the unfortunatley-named 'unlazy_fpu()'.
> 
> This patch introduces a new helper which will do both of
> those things internally.
> 
> Note that this requires a patch from Oleg in order to work
> properly.  It is currently in tip/x86/fpu.
> 
> > commit f893959b0898bd876673adbeb6798bdf25c034d7
> > Author: Oleg Nesterov <oleg@redhat.com>
> > Date:   Fri Mar 13 18:30:30 2015 +0100
> >
> >    x86/fpu: Don't abuse drop_init_fpu() in flush_thread()
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: bp@alien8.de
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Suresh Siddha <sbsiddha@gmail.com>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Fenghua Yu <fenghua.yu@intel.com>
> Cc: the arch/x86 maintainers <x86@kernel.org>

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>