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Re: [Qemu-devel] [PATCH] kvm: First step to push iothread lock out of in

From: Jan Kiszka
Subject: Re: [Qemu-devel] [PATCH] kvm: First step to push iothread lock out of inner run loop
Date: Sun, 24 Jun 2012 16:08:04 +0200
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On 2012-06-24 10:49, Avi Kivity wrote:
> On 06/23/2012 02:45 PM, Jan Kiszka wrote:
>> Hmm, we may need the iothread lock around cpu_set_apic_tpr for
>> !kvm_irqchip_in_kernel(). And as we are at it, apic_base manipulation
>> can be but there as well.
>> With in-kernel irqchip, there is no such need. Also, no one accesses
>> eflags outside of the vcpu thread, independent of the irqchip mode.
> In fact !kvm_irqchip_in_kernel() is broken wrt the tpr.  Interrupt
> injection needs to be done atomically, but currently we check the tpr
> from the injecting thread, which means the cpu thread can race with it.
>  We need to move the check to the vcpu thread so that the guest vcpu is
> halted.

So apic_set_irq basically needs to be deferred to vcpu context, right?
Will have a look.


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