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Date:   Mon, 10 May 2021 14:53:46 -0300
From:   Marcelo Tosatti <mtosatti@redhat.com>
To:     Peter Xu <peterx@redhat.com>
Cc:     kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Sean Christopherson <seanjc@google.com>
Subject: Re: [patch 1/4] KVM: x86: add start_assignment hook to kvm_x86_ops
Message-ID: <20210510175346.GA48272@fuller.cnet>
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On Fri, May 07, 2021 at 03:16:00PM -0400, Peter Xu wrote:
> On Fri, May 07, 2021 at 10:06:10AM -0300, Marcelo Tosatti wrote:
> > Add a start_assignment hook to kvm_x86_ops, which is called when 
> > kvm_arch_start_assignment is done.
> > 
> > The hook is required to update the wakeup vector of a sleeping vCPU
> > when a device is assigned to the guest.
> > 
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> > 
> > Index: kvm/arch/x86/include/asm/kvm_host.h
> > ===================================================================
> > --- kvm.orig/arch/x86/include/asm/kvm_host.h
> > +++ kvm/arch/x86/include/asm/kvm_host.h
> > @@ -1322,6 +1322,7 @@ struct kvm_x86_ops {
> >  
> >  	int (*update_pi_irte)(struct kvm *kvm, unsigned int host_irq,
> >  			      uint32_t guest_irq, bool set);
> > +	void (*start_assignment)(struct kvm *kvm, int device_count);
> 
> I'm thinking what the hook could do with the device_count besides comparing it
> against 1...
> 
> If we can't think of any, perhaps we can directly make it an enablement hook
> instead (so we avoid calling the hook at all when count>1)?
> 
>    /* Called when the first assignment registers (count from 0 to 1) */
>    void (*enable_assignment)(struct kvm *kvm);

Sure, sounds good, just kept the original name...