Re: [PATCH 5/5] Fix kdump under KVM.

[Chris Lalancette <clalance@redhat.com>]

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@lists.sourceforge.net/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?

-- 
Chris Lalancette