linux-kernel - Re: [PATCH] kvm: make vcpu life cycle separated from kvm instance

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Message-ID: <20111205101842.GH12507@redhat.com>
Date:	Mon, 5 Dec 2011 12:18:42 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Liu ping fan <kernelfans@...il.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, aliguori@...ibm.com,
	jan.kiszka@....de
Subject: Re: [PATCH] kvm: make vcpu life cycle separated from kvm instance

On Mon, Dec 05, 2011 at 11:58:56AM +0200, Avi Kivity wrote:
> On 12/05/2011 11:42 AM, Gleb Natapov wrote:
> > On Mon, Dec 05, 2011 at 11:30:51AM +0200, Avi Kivity wrote:
> > > On 12/05/2011 07:29 AM, Liu ping fan wrote:
> > > > like this,
> > > > #define kvm_for_each_vcpu(idx, cnt, vcpup, kvm) \
> > > > 	for (idx = 0, cnt = 0, vcpup = kvm_get_vcpu(kvm, idx); \
> > > > 	     cnt < atomic_read(&kvm->online_vcpus) && \
> > > > 	     idx < KVM_MAX_VCPUS; \
> > > > 	     idx++, (vcpup == NULL)?:cnt++, vcpup = kvm_get_vcpu(kvm, idx)) \
> > > > 	     if (vcpup == NULL) \
> > > > 	          continue; \
> > > > 	     else
> > > >
> > > >
> > > > A little ugly, but have not thought a better way out :-)
> > > >
> > > 
> > > #define kvm_for_each_vcpu(vcpu, it) for (vcpu = kvm_fev_init(&it); vcpu;
> > > vcpu = kvm_fev_next(&it, vcpu))
> > > 
> > > Though that doesn't give a good place for rcu_read_unlock().
> > > 
> > > 
> > Why not use rculist to store vcpus and use list_for_each_entry_rcu()?
> 
> We can, but that's a bigger change.
> 
Is it? I do not see a lot of accesses to vcpu array except those loops.

--
			Gleb.
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