On 03/13/2012 05:16 AM, H. Peter Anvin wrote:
On 03/12/2012 01:04 PM, H. Peter Anvin wrote:On 03/12/2012 01:01 PM, Eric W. Biederman wrote:The basic problem is which source do we block this at? How many sources are their? And architecturally last I looked x86 no longer has a NMI disable EFI and similar systems want to get away without a CMOS legacy clock because designers so often get them wrong.On all processors which have an LAPIC you can block all NMI sources at the LAPIC. I think it's safe to assume that if you don't have an LAPIC -- an ancient system by now -- you have port 70h.One thing: *disabling* the LAPIC will allow external NMIs coming in on LINT1 through, since the LAPIC in the disabled state tries to mimic the no-LAPIC configuration. So I don't think you want to disable LAPIC as much as disable the interrupt vectors within.
Does this sound like a plan to get the ball rolling?: 1.- Merge Don's patch to disable the LAPIC in kdump reboot path (this fixes a real issue seen in the field, is a net win and certainly not a regression - indeed it makes the code simpler because the I/O APICs are left untouched). 2.- Merge my patch set to ignore early NMIs (this brings the behavior of the boot code in line with what we do in the rest of the kernel a we can avoid situations were a spurious NMI causes the kernel to halt). The early NMI handler is temporary and the final NMI handler installed shortly afterwards will take care of subsequent NMIs. 3.- Make sure that spurious NMIs (i.e. NMIs that for whatever reason could not be stopped at the source) received during the reboot path to the kdump kernel do not cause a triple fault or a system lockup. This is under testing. 4.- Identify all the NMI sources and keep them from reaching the CPU when it can be done in a race-free way. Can we get 1 and 2 merged while we work on further improvements (3 and 4)? Thanks, Fernando -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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