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

[Aravind Gopalakrishnan]

> Ok, this return is still bugging me - we're logging the error which
> caused the counter overflow but we go and explicitly clear _STATUS so
> that machine_check_poll doesn't pick up the same error again.
>
> Even though, machine_check_poll is intended to log the thresholding
> error.
>
> Which actually makes me think that that machine_check_poll is actually
> completely useless there. IOW, how about that instead:
>
> ---
> From: Chen Yucong <slaoub@xxxxxxxxx <mailto:slaoub@xxxxxxxxx>>
> Date: Thu, 2 Oct 2014 14:48:19 +0200
> Subject: [PATCH] x86, MCE, AMD: Correct thresholding error logging
>
> mce_setup() does not gather the content of IA32_MCG_STATUS, so it
> should be read explicitly. Moreover, we need to clear IA32_MCx_STATUS
> to avoid that mce_log() logs the processed threshold event again
> at next time.
>
> But we do the logging ourselves and machine_check_poll() is completely
> useless there. So kill it.
>
> Signed-off-by: Chen Yucong <slaoub@xxxxxxxxx <mailto:slaoub@xxxxxxxxx>>
> Signed-off-by: Borislav Petkov <bp@xxxxxxx <mailto:bp@xxxxxxx>>
> ---
>  arch/x86/kernel/cpu/mcheck/mce_amd.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c 
> b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> index 1c54d3d61a4d..9ce64955559d 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> @@ -270,14 +270,13 @@ void mce_amd_feature_init(struct cpuinfo_x86 *c)
>  static void amd_threshold_interrupt(void)
>  {
>         u32 low = 0, high = 0, address = 0;
> +       int cpu = smp_processor_id();
>         unsigned int bank, block;
>         struct mce m;
>
> -       mce_setup(&m);
> -
>         /* assume first bank caused it */
>         for (bank = 0; bank < mca_cfg.banks; ++bank) {
> -               if (!(per_cpu(bank_map, m.cpu) & (1 << bank)))
> +               if (!(per_cpu(bank_map, cpu) & (1 << bank)))
>                         continue;
>                 for (block = 0; block < NR_BLOCKS; ++block) {
>                         if (block == 0) {
> @@ -309,20 +308,21 @@ static void amd_threshold_interrupt(void)
>                          * Log the machine check that caused the threshold
>                          * event.
>                          */
> -                       machine_check_poll(MCP_TIMESTAMP,
> -  &__get_cpu_var(mce_poll_banks));
> -
> -                       if (high & MASK_OVERFLOW_HI) {
> -                               rdmsrl(address, m.misc);
> -  rdmsrl(MSR_IA32_MCx_STATUS(bank), m.status);
> -                               m.bank = K8_MCE_THRESHOLD_BASE
> -                                      + bank * NR_BLOCKS
> -                                      + block;
> -                               mce_log(&m);
> -                               return;
> -                       }
> +                       if (high & MASK_OVERFLOW_HI)
> +                               goto log;
>                 }
>         }
> +       return;
> +
> +log:
> +       mce_setup(&m);
> +       rdmsrl(MSR_IA32_MCG_STATUS, m.mcgstatus);
> +       rdmsrl(address, m.misc);
> +       rdmsrl(MSR_IA32_MCx_STATUS(bank), m.status);
> +       m.bank = K8_MCE_THRESHOLD_BASE + bank * NR_BLOCKS + block;


I am not understanding why m.bank is assigned this value..

It only causes incorrect decoding-
[  608.832916] DEBUG: raise_amd_threshold_event
[  608.832926] [Hardware Error]: Corrected error, no action required.
[  608.833143] [Hardware Error]: CPU:26 (15:2:0) 
MC165_STATUS[-|CE|MiscV|-|AddrV|-|-]: 0x8c00000000000000
[  608.833551] [Hardware Error]: MC165_ADDR: 0x0000000000000000
[  608.833777] [Hardware Error]: cache level: RESV, tx: INSN
[  608.834034] amd_inject module loaded ...


(Obviously, as in amd_decode_mce() we switch (m->bank) for decoding the 
status and there is no bank 165)

OTOH, if m.bank = bank;
Then we get correct decoding info-
[   58.021978] DEBUG: raise_amd_threshold_event
[   58.021992] [Hardware Error]: Corrected error, no action required.
[   58.022155] [Hardware Error]: CPU:0 (15:60:0) 
MC4_STATUS[-|CE|MiscV|-|AddrV|-|-]: 0x8c00000000000000
[   58.022393] [Hardware Error]: MC4_ADDR: 0x0000000000000000
[   58.022531] [Hardware Error]: MC4 Error (node 0): DRAM ECC error 
detected on the NB.
<snip..it's throws WARN as "Something is rotten in the state of Denmark".>
<.. but that's fine. we are just fake-injecting errors here.. :) >
[   58.022933] [Hardware Error]: cache level: RESV, tx: INSN
[   58.023084] amd_inject module loaded ...

Thanks,
-Aravind.

> +       mce_log(&m);
> +
> +       wrmsrl(MSR_IA32_MCx_STATUS(bank), 0);
>  }
>
>  /*
> --
> 2.0.0
>
> --
> Regards/Gruss,
>     Boris.

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