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Re: [Qemu-devel] [RFC PATCH] hw/arm/virt: Added preliminary GICv3 suppor

From: Pavel Fedin
Subject: Re: [Qemu-devel] [RFC PATCH] hw/arm/virt: Added preliminary GICv3 support for kvm mode
Date: Thu, 21 May 2015 17:10:07 +0300


> So to me it is sensible to instantiate GICV2 through legacy
> KVM_CREATE_IRQCHIP API if both KVM_CREATE_DEVICE(test mode=true) failed.

 I disagree because at this point we already know which GIC version the user 
wants. This
is because kvm_irqchip_create() is called after machine instance is created (and
virt_instance_init() has been called). At this point we already know all the 
options. At
this point i think the scenario should be:
 a) If we want GICv3 - test for KVM_CREATE_DEVICE(GICv3) and fail if we don't 
have one.
 b) If we want GICv2 - test for KVM_CREATE_DEVICE(GICv2). If it fails, try
 IMHO there is little sense to fall back from v3 to v2 or vice versa because 
important parameters (like number of CPUs) depend on it.
 Implementing this behavior costs only one more integer in MachineState 
structure. Is it
too large ? If you want, i can post my patches as RFC, i think now they are 
more or less

Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia

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