Messages in this thread | | | Date | Mon, 01 Apr 2013 13:26:34 +0800 | From | Zhenzhong Duan <> | Subject | Re: [PATCH] xen: Don't call arch_trigger_all_cpu_backtrace in dom0(pvm) |
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On 2013-03-29 21:46, Konrad Rzeszutek Wilk wrote: > On Fri, Mar 29, 2013 at 03:22:38PM +0800, Zhenzhong Duan wrote: >> nmi isn't supported in dom0, fallback to general all cpu backtrace code. >> >> Without fix, on xapic system, sysrq+l, no backtrace is showed. >> On x2apic enabled system, got NULL pointer dereference as below. > Why would the x2APIC or xAPIC make a difference here? The Linux dom0 > is not fiddling with the APIC - that is the hypervisor job. In x2apic enabled system, dom0 kernel set apic pointer to apic_x2apic_cluster or apic_x2apic_phys. When sending nmi, apic->send_IPI_all copy cpumask which isn't initialized. For xapic system, apic->send_IPI_all=xen_send_IPI_all apic, this func does nothing for nmi, so no backtrace. > Can you explain to me why x2apic_send_IPI_mask is even set? Wouldn't > the Xen version of send_IPI be present? (See xen_smp_ops) It's overwrited by x2apic initialization. The problem is even without overwrite, like xapic system, xen_send_IPI_all doesn't work for nmi vector. zduan
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