From: Avi Kivity <avi@redhat.com>
To: "Nadav Har'El" <nyh@math.technion.ac.il>
Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v3 2/3] KVM: send IPI to vcpu only when it's in guest mode
Date: Wed, 12 Jan 2011 11:59:47 +0200 [thread overview]
Message-ID: <4D2D7B93.40109@redhat.com> (raw)
In-Reply-To: <20110112095428.GA15835@fermat.math.technion.ac.il>
On 01/12/2011 11:54 AM, Nadav Har'El wrote:
> On Wed, Jan 12, 2011, Xiao Guangrong wrote about "[PATCH v3 2/3] KVM: send IPI to vcpu only when it's in guest mode":
> > We can interrupt the vcpu only when it's running in guest mode
> > to reduce IPI
>
> Hi,
>
> I am afraid there's a risk of confusion between the new
>
> vcpu->mode = IN_GUEST_MODE;
>
> and the existing
>
> is_guest_mode() (i.e., vcpu->arch.hflags& HF_GUEST_MASK)
>
> The latter says that the virtual cpu is in guest mode (i.e., the guest used
> VMLAUNCH and is runnning a nested guest), while the former says that the
> physical CPU that this vcpu is currently being run on, is in guest mode - or
> in other words, this vcpu is currently running.
>
> I'm not sure what is the best way to resolve this potential for confusion.
> Maybe on of them is better renamed (e.g., instead of vcpu->mode = IN_GUEST_MODE
> have something like vcpu->running = NOW_RUNNING). Or maybe some good comments
> need to to be written to explain the situation.
>
> Actually, I just noticed that there's already a vcpu->guest_mode which you
> are apparently replacing, so the potential for confusion is already in the
> current code... I.e., in the current code, is_guest_mode(vcpu) does NOT check
> vcpu->guest_mode...
>
Right. One is from the host's point of view, the other is from the
guest's point of view. I'll rename is_guest_mode() to is_nested_guest().
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2011-01-12 10:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-12 7:39 [PATCH v3 1/3] KVM: fix rcu usage warning in kvm_arch_vcpu_ioctl_set_sregs() Xiao Guangrong
2011-01-12 7:40 ` [PATCH v3 2/3] KVM: send IPI to vcpu only when it's in guest mode Xiao Guangrong
2011-01-12 9:54 ` Nadav Har'El
2011-01-12 9:59 ` Avi Kivity [this message]
2011-01-12 7:41 ` [PATCH v3 3/3] KVM: make make_all_cpus_request() lockless Xiao Guangrong
2011-01-19 5:16 ` [PATCH v3 1/3] KVM: fix rcu usage warning in kvm_arch_vcpu_ioctl_set_sregs() Xiao Guangrong
2011-01-19 18:13 ` Marcelo Tosatti
2011-01-20 3:03 ` Xiao Guangrong
2011-01-20 15:27 ` Marcelo Tosatti
2011-01-27 2:35 ` Xiao Guangrong
2011-01-27 13:15 ` Avi Kivity
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