On Thu, Feb 07, 2008 at 01:24:04PM +0100, Ingo Molnar wrote: > > * Neil Horman <[EMAIL PROTECTED]> wrote: > > > Ingo noted a few posts down the nmi_exit doesn't actually write to the > > APIC EOI register, so yeah, I agree, its bogus (and I apologize, I > > should have checked that more carefully). Nevertheless, this patch > > consistently allowed a hangning machine to boot through an Nmi lockup. > > So I'm forced to wonder whats going on then that this patch helps > > with. perhaps its a just a very fragile timing issue, I'll need to > > look more closely. > > try a dummy iret, something like: > > asm volatile ("pushf; push $1f; iret; 1: \n"); > > to get the CPU out of its 'nested NMI' state. (totally untested) > > the idea is to push down an iret frame to the kernel stack that will > just jump to the next instruction and gets it out of the NMI nesting. > Note: interrupts will/must still be disabled, despite the iret. (the > ordering of the pushes might be wrong, we might need more than that for > a valid iret, etc. etc.) > > Ingo
Just tried this experiment and it met with success. Executing a dummy iret instruction got us to boot the kdump kernel successfully. Thoughts on how we should handle this from here? Regards Neil -- /**************************************************** * Neil Horman <[EMAIL PROTECTED]> * Software Engineer, Red Hat ****************************************************/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/