linux-kernel - Re: [PATCHV3 1/3] x86, ras: Add new infrastructure for machine check fixup tables

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Date:	Wed, 16 Dec 2015 09:55:11 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Tony Luck <tony.luck@...el.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Robert <elliott@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	linux-nvdimm <linux-nvdimm@...1.01.org>, X86 ML <x86@...nel.org>
Subject: Re: [PATCHV3 1/3] x86, ras: Add new infrastructure for machine check
 fixup tables

On Tue, Dec 15, 2015 at 5:29 PM, Tony Luck <tony.luck@...el.com> wrote:
> Copy the existing page fault fixup mechanisms to create a new table
> to be used when fixing machine checks. Note:
> 1) At this time we only provide a macro to annotate assembly code
> 2) We assume all fixups will in code builtin to the kernel.
> 3) Only for x86_64
> 4) New code under CONFIG_MCE_KERNEL_RECOVERY (default 'n')
>
> Signed-off-by: Tony Luck <tony.luck@...el.com>

Looks generally good.

Reviewed-by: Andy Lutomirski <luto@...nel.org>

with trivial caveats:


>  int __init mcheck_init(void)
>  {
> +#ifdef CONFIG_MCE_KERNEL_RECOVERY
> +       if (__stop___mcex_table > __start___mcex_table)
> +               sort_extable(__start___mcex_table, __stop___mcex_table);
> +#endif

This doesn't matter unless we sprout a lot of these, but it could be
worthwhile to update sortextable.h as well.

> +#ifdef CONFIG_MCE_KERNEL_RECOVERY
> +int fixup_mcexception(struct pt_regs *regs)
> +{
> +       const struct exception_table_entry *fixup;
> +       unsigned long new_ip;
> +
> +       fixup = search_mcexception_tables(regs->ip);
> +       if (fixup) {
> +               new_ip = ex_fixup_addr(fixup);
> +
> +               regs->ip = new_ip;

You could very easily save a line of code here :)

> +               return 1;
> +       }
> +
> +       return 0;
> +}
> +#endif
> +

--Andy
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