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Re: [Xen-devel] [PATCH 0 of 6] Fix kexec in Xen (take 3)

To: "Andrew Cooper" <andrew.cooper3@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0 of 6] Fix kexec in Xen (take 3)
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Wed, 25 May 2011 17:14:49 +0100
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>>> On 25.05.11 at 16:32, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> This set of patches is designed to get the kexec path working again on Xen 
> 4.x
> kdump kernels can't boot if x2apic mode is enabled and the ACPI tables dont 
> state this fact.  They also cant boot at all with interrupt remapping 
> enabled.
> These patches cause xen to track the BSP local APIC boot state and return to 
> it before kexec'ing to a new kernel.  It also makes sure to disable IO 
> virtualisation.

I was about to reply to the individual patches, but they just seem
too inconsistent to me (comments not matching code, without it
being clear whether code or comment is wrong; functions introduced
that have no callers). Can you work on getting them into a
state suitable for reviewing?

Further I don't buy your pseudo-quoting of the MP spec saying
that secondary CPUs' local APICs have to be disabled. Keir already
pointed out on your previous submission that in order for them to
receive the INIT and Startup IPIs they must be enabled.


> One area which is problematic is disabling interrupt remapping.  
> lapic_suspend() calls iommu_disable_x2apic_IR() which in a previous thread 
> was deemed to be Intel specific and only works by chance on AMD boxes by 
> effectivly being a NOP.  As lapic_suspend() is generic code, does this mean 
> that we can't/don't ever disable interrupt remapping on AMD boxes?
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
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