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



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