Messages in this thread | | | From | "Luck, Tony" <> | Subject | RE: [RFC PATCH] x86, entry: Switch stacks on a paranoid entry from userspace | Date | Thu, 13 Nov 2014 00:31:30 +0000 |
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> v2's not going to make a difference unless you're using uprobes at the > same time.
Not (knowingly) using uprobes. System is installed with a RHEL7 userspace ... but is essentially idle except for my test program.
> In the interest of my sanity, can you add something like > BUG_ON(!user_mode_vm(regs)) or the mce_panic equivalent before calling > memory_failure?
I don't think that can possibly trip - we can only end up with a recoverable error from a user mode access. But I'll see about adding it anyway
> What happens if there's a shared bank but the actual offender has a > higher order than the cpu that finds the error?
This test case injects a memory error which is logged in bank1. This bank is shared by the two hyperthreads that are on the same core. The mce_severity() function distinguishes which is the active thread and which the innocent bystander by looking at MCG_STATUS. In the active thread MCG_STATUS.EIPV is 1, in the bystander it is 0. The returned severity is MCE_AR_SEVERITY for the thread that hit the error, MCE_KEEP_SEVERITY for the bystander. So it doesn't matter which thread has the lower order and sees it first.
> Is this something I can try under KVM?
I don't know if KVM has a way to simulate a machine check event.
-Tony
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