Re: [PATCH 4/4] kvm, mem-hotplug: Update apic access page when it is migrated.

[Nadav Amit]

On 7/7/14, 2:54 PM, Gleb Natapov wrote:
> On Mon, Jul 07, 2014 at 02:42:27PM +0300, Nadav Amit wrote:
> > Tang,
> >
> > Running some (unrelated) tests I see that KVM does not handle APIC base
> > relocation correctly. When the base is changed, kvm_lapic_set_base just
> > changes lapic->base_address without taking further action (i.e., modifying
> > the VMCS apic address in VMX).
> >
> > This patch follows KVM bad behavior by using the constant
> > VMX_APIC_ACCESS_PAGE_ADDR instead of lapic->base_address.
> There is no OS out there that relocates APIC base (in fact it was not always
> relocatable on real HW), so there is not point in complicating the code to support
> it. In fact current APIC_ACCESS_ADDR handling relies on the fact that all vcpus
> has apic mapped at the same address.
>
> > Anyhow, I didn't see anything that would make my life (in fixing the lapic
> > base issue) too difficult. Yet, feel free in making it more "fix-friendly".
> Why would you want to fix it?
If there is no general need, I will not send a fix. However, I think the 
very least a warning message should be appear if the guest relocates the 
APIC base.

Nadav

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