Marcelo Tosatti wrote: > On Wed, Oct 28, 2009 at 11:21:42AM +0100, Chris Lalancette wrote: >> Marcelo Tosatti wrote: >>> On Tue, Oct 27, 2009 at 05:41:07PM +0100, Chris Lalancette wrote: >>>> This patch is the main point of the series. In order for >>>> kdump to properly work inside a KVM guest, we need to make >>>> sure that all VCPUs in virtual wire APIC mode get kicked >>>> to try and pick up the timer interrupts. To do this, >>>> we iterate over the CPUs and deliver interrupts to the >>>> proper VCPUs. >>>> >>>> I don't love the concept of doing kvm_irq_kick_vcpus() from >>>> within pit_timer_fn(). A PIT is not connected to a CPU at all, >>>> only to a PIC or APIC. However, if a CPU enters idle, this is >>>> the only way to wake it up to check for the interrupt. >>> The reason the PIT interrupt was fixed to BSP is: >>> >>> http://www.mail-archive.com/kvm-devel@xxxxxxxxxxxxxxxxxxxxx/msg13250.html >>> >>> Perhaps enhancing ioapic_deliver's (irq == 0) check to bypass the >>> destination overwrite in case its programmed by the guest to >>> a single CPU would fix it? >> Ug, nasty. I definitely don't want to re-introduce that bug. What exactly do >> you mean by "fix it"? Do you mean fix the original RHEL-5.1 PAE issue, or fix >> the kdump issue? > > The kdump issue. Something like: > > #ifdef CONFIG_X86 > /* Always delivery PIT interrupt to vcpu 0 */ > if (irq == 0 && dest_multiple_vcpus(entry)) { > irqe.dest_mode = 0; /* Physical mode. */ > /* need to read apic_id from apic regiest since > * it can be rewritten */ > irqe.dest_id = ioapic->kvm->bsp_vcpu->vcpu_id; > } > #endif > > The rest of the code should be ready to deal with it. Do you have any more information about how to reproduce that original issue? I tried installing a RHEL-5.1 i386 guest with a PAE kernel, and I was able to install and boot it just fine with or without the "always deliver irq 0 to vcpu 0" check above. Either there's something in particular I need to do to trigger the issue (hardware or software), or it's being solved another way. In the meantime, I've gotten the "set_irq from IRQ context" that Avi suggested working, and the fixing up of this IOAPIC check is the last bit to actually get kdump working. -- Chris Lalancette -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
