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    SubjectRe: [RFC PATCH 02/16] x86/split_lock: Handle #AC exception for split lock in kernel mode
    On Sat, 23 Jun 2018, Fenghua Yu wrote:

    > On Sun, Jun 24, 2018 at 02:55:08AM +0200, Thomas Gleixner wrote:
    > > On Sat, 23 Jun 2018, Fenghua Yu wrote:
    > > > On Sat, Jun 23, 2018 at 11:17:03AM +0200, Thomas Gleixner wrote:
    > > > > On Fri, 22 Jun 2018, Fenghua Yu wrote:
    > > It's not treated as failure. The firmware simply does not have an handler
    > > for #AC installed and dies. I hope you yelled at the firmware people
    > > already.
    >
    > I think firmware does handle the split lock in its #AC handler because
    > firmware shows the following log and system hangs:
    >
    > !!!! IA32 Exception Type - 11(#AC - Alignment Check) CPU Apic ID - 00000014!
    > !
    > ExceptionData - 00000000
    > EIP - 6A9DB6C3, CS - 00000010, EFLAGS - 00010006
    > ...

    They even have a handler which makes the thing die, but never bothered to
    enable #AC in the first place. So the handler is there to catch the case
    that an operating system dares to enable #AC. Thank god, I don't have to
    review that source code.

    Thanks,

    tglx

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