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

Aravind Gopalakrishnan
2014-10-08T21:52:20Z

>
> 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@gmail.com <mailto:slaoub@gmail.com>>
> 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@gmail.com <mailto:slaoub@gmail.com>>
> Signed-off-by: Borislav Petkov <bp@suse.de <mailto:bp@suse.de>>
> ---
> 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.