linux-kernel - Re: [PATCH 1/4 Rebase] x86, MCE: Provide a lock-less memory pool to save error record

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Date:	Fri, 22 May 2015 17:06:55 -0400
From:	"Chen, Gong" <gong.chen@...ux.intel.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	linux-kernel@...r.kernel.org, tony.luck@...el.com
Subject: Re: [PATCH 1/4 Rebase] x86, MCE: Provide a lock-less memory pool to
 save error record

On Wed, May 20, 2015 at 12:36:10PM +0200, Borislav Petkov wrote:
> Date: Wed, 20 May 2015 12:36:10 +0200
> From: Borislav Petkov <bp@...e.de>
> To: "Chen, Gong" <gong.chen@...ux.intel.com>
> Cc: linux-kernel@...r.kernel.org, tony.luck@...el.com
> Subject: Re: [PATCH 1/4 Rebase] x86, MCE: Provide a lock-less memory pool
>  to save error record
> User-Agent: Mutt/1.5.23 (2014-03-12)
> 
> On Wed, May 20, 2015 at 03:35:35PM -0400, Chen, Gong wrote:
> > printk is not safe to use in MCE context. Add a lockless memory
> > allocator pool to save error records in MCE context. Issual of those
> > records will be delayed to a context safe to do printk. This idea is
> > inspired by APEI/GHES driver.
> > 
> > We're very conservative and allocate only two pages for it but since
> > we're going to use those pages throughout the system's lifetime, we
> > allocate them statically to avoid early boot time allocation woes.
> > 
> > Signed-off-by: Chen, Gong <gong.chen@...ux.intel.com>
> > Link: http://lkml.kernel.org/r/1407830375-11087-1-git-send-email-gong.chen@linux.intel.com
> > [Boris: rewrite. ]
> > Signed-off-by: Borislav Petkov <bp@...e.de>
> > ---
> >  arch/x86/Kconfig                          |   1 +
> >  arch/x86/include/uapi/asm/mce.h           |   3 +-
> >  arch/x86/kernel/cpu/mcheck/Makefile       |   2 +-
> >  arch/x86/kernel/cpu/mcheck/mce-genpool.c  | 102 ++++++++++++++++++++++++++++++
> >  arch/x86/kernel/cpu/mcheck/mce-internal.h |  12 ++++
> >  arch/x86/kernel/cpu/mcheck/mce.c          |   8 ++-
> >  6 files changed, 125 insertions(+), 3 deletions(-)
> >  create mode 100644 arch/x86/kernel/cpu/mcheck/mce-genpool.c
> 
> Applied, thanks...
> 
> > diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> > index e535533d5ab8..ba91777a7ad8 100644
> > --- a/arch/x86/kernel/cpu/mcheck/mce.c
> > +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> > @@ -115,7 +115,7 @@ static void (*quirk_no_way_out)(int bank, struct mce *m, struct pt_regs *regs);
> >   * CPU/chipset specific EDAC code can register a notifier call here to print
> >   * MCE errors in a human-readable form.
> >   */
> > -static ATOMIC_NOTIFIER_HEAD(x86_mce_decoder_chain);
> > +ATOMIC_NOTIFIER_HEAD(x86_mce_decoder_chain);
> >  
> >  /* Do initial initialization of a struct mce */
> >  void mce_setup(struct mce *m)
> > @@ -1688,6 +1688,12 @@ void mcheck_cpu_init(struct cpuinfo_x86 *c)
> >  	if (mca_cfg.disabled)
> >  		return;
> >  
> > +	if (mce_genpool_init()) {
> > +		mca_cfg.disabled = true;
> > +		pr_emerg("Couldn't allocate MCE records pool!\n");
> > +		return;
> > +	}
> > +
> >  	if (__mcheck_cpu_ancient_init(c))
> >  		return;
> 
> ... and moved this pool initialization right before we assign
> machine_check_vector so that we don't do it unnecessarily if we return
> earlier due to missing MCA features/MCA not enabled.
> 
IIRC, I don't need to post a new patch again, right?

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