Re: [PATCH] x86, MCE, AMD: save IA32_MCi_STATUS before machine_check_poll() resets it

Borislav Petkov
2014-09-29T12:05:52Z

On Tue, Sep 23, 2014 at 04:19:14PM +0800, Chen Yucong wrote:
> machine_check_poll() will reset IA32_MCi_STATUS register to zero.
> So we need to save the content of IA32_MCi_STATUS MSRs before
> calling machine_check_poll() for logging threshold interrupt event.
>
> mce_setup() does not gather the content of IA32_MCG_STATUS, so it
> should be read explicitly.
>
> Signed-off-by: Chen Yucong <slaoub@gmail.com>
> ---
> arch/x86/kernel/cpu/mcheck/mce_amd.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> index f8c56bd..9148b4d 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> @@ -275,6 +275,12 @@ static void amd_threshold_interrupt(void)
>
> mce_setup(&m);
>
> + /*
> + * mce_setup() can't gather the content of IA32_MCG_STATUS,
> + * so it should be read explicitly.
> + */

No need for that comment.

> + rdmsrl(MSR_IA32_MCG_STATUS, m.mcgstatus);
> +
> /* assume first bank caused it */
> for (bank = 0; bank < mca_cfg.banks; ++bank) {
> if (!(per_cpu(bank_map, m.cpu) & (1 << bank)))
> @@ -305,6 +311,12 @@ static void amd_threshold_interrupt(void)
> (high & MASK_LOCKED_HI))
> continue;
>
> + /*
> + * machine_check_poll() will reset IA32_MCi_STATUS
> + * register to zero, save it for use later.
> + */
> + rdmsrl(MSR_IA32_MCx_STATUS(bank), m.status);

Actually, to be more future-proof, I'd like to do the AMD-specific
logging first, i.e. before machine_check_poll() so that any future
changes there don't influence what we do in mce_amd.c.

So please move the machine_check_poll() call behind the

if (high & MASK_OVERFLOW_HI) {

test and drop the return.

But the patch makes sense so good catch!

Thanks.

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
--