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    SubjectRe: [PATCH 05/10] MCE: Mask out address mask bits below address granuality
    On Fri, Jun 10, 2011 at 04:07:13AM -0400, Hidetoshi Seto wrote:
    > (2011/06/10 6:33), Luck, Tony wrote:
    > > From: Andi Kleen <andi@firstfloor.org>
    > >
    > > SER enabled systems report the address granuality for each
    > > reported address in a machine check. But the bits below
    > > the granuality are undefined. Mask them out before
    > > logging the machine check.
    > >
    > > Signed-off-by: Andi Kleen <ak@linux.intel.com>
    > > Signed-off-by: Tony Luck <tony.luck@intel.com>
    > > ---
    > > arch/x86/kernel/cpu/mcheck/mce.c | 12 +++++++++++-
    > > 1 files changed, 11 insertions(+), 1 deletions(-)
    > >
    > > diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
    > > index 0349e87..ffc8d11 100644
    > > --- a/arch/x86/kernel/cpu/mcheck/mce.c
    > > +++ b/arch/x86/kernel/cpu/mcheck/mce.c
    > > @@ -539,8 +539,18 @@ static void mce_read_aux(struct mce *m, int i)
    > > {
    > > if (m->status & MCI_STATUS_MISCV)
    > > m->misc = mce_rdmsrl(MSR_IA32_MCx_MISC(i));
    > > - if (m->status & MCI_STATUS_ADDRV)
    > > + if (m->status & MCI_STATUS_ADDRV) {
    > > m->addr = mce_rdmsrl(MSR_IA32_MCx_ADDR(i));
    > > +
    > > + /*
    > > + * Mask the reported address by the reported granuality.
    > > + */
    > > + if (mce_ser && (m->status & MCI_STATUS_MISCV)) {
    > > + u8 shift = m->misc & 0x1f;
    > > + m->addr >>= shift;
    > > + m->addr <<= shift;
    > > + }
    > > + }
    > > }
    > >
    > > DEFINE_PER_CPU(unsigned, mce_poll_count);
    >
    > Why do you have to mask it out in kernel, why not in user/logger?
    >
    > One possible story is:
    > "... the brand-new Xeon XXXX has new MCx_***_VALID bit in ****
    > register, if it is set the lower bits of MCx_ADDR indicates
    > ****, otherwise the bits are undefined ..."
    >
    > So I think that kernel should convey the raw value from hardware to
    > userland. Even if it contains some noise on it, user can determine
    > whether it is useful or not. And more, since this is an error record,
    > there will be no second chance to retrieve the data afterward.

    I think they need the correct address for the poisoning later:

    if (severity == MCE_AO_SEVERITY && mce_usable_address(&m))
    mce_ring_add(m.addr >> PAGE_SHIFT);


    Tony?

    --
    Regards/Gruss,
    Boris.

    Advanced Micro Devices GmbH
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    General Managers: Alberto Bozzo, Andrew Bowd
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