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Date: Sat, 2 May 2009 10:40:41 +0300
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCH  0/8] kvm: Fixes, cleanups and live
	migration
Message-ID: <20090502074041.GB7198@redhat.com>
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To: Anthony Liguori <aliguori@us.ibm.com>
Cc: Jan Kiszka <jan.kiszka@web.de>, Avi Kivity <avi@redhat.com>, qemu-devel@nongnu.org

On Fri, May 01, 2009 at 05:40:00PM -0500, Anthony Liguori wrote:
> Jan Kiszka wrote:
>> Besides refreshed versions of my already posted fixes and cleanups for
>> KVM, this series comes with patches to enable live migration in KVM
>> mode. If there is still some migration bit missing compared to qemu-kvm,
>> please let me know.
>>   
>
> In qemu-kvm, we also save:
>
> MSR_IA32_TSC
> mp_state
> interrupt_bitmap
>
> In QEMU, we probably should just emulate MSR_IA32_TSC and then we can  
> reuse that for save/restore.
>
> interrupt_bitmap is a bit more tricky.  It only ever can have one bit  
> set AFAICT but I don't see anything that we're currently saving that  
> maps to it which leads me to wonder why KVM needs it and QEMU doesn't.
>
KVM stores pending interrupt there (interrupt that is not in irq chip
already but not yet injected to vcpu). I have patch (not yet submitted)
that removes the use of interrupt_bitmap from kernel. It recreated only
for migration bits. My plan is to change migration bits too, but it is
trickier if we want to keep backwards compatibility. No need to
introduce interrupt_bitmap in qemu upstream IMO. We need to migrate
pending interrupt though. The info that should be migrated it interrupt
vector, interrupt type (soft/hw) and instruction length (needed for
injection of soft interrupts on VMX).

--
			Gleb.