linux-kernel - Re: [PATCH 0/3] KVM: Introduce VCPU-wide notion of guest-mode V2

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Message-ID: <20101201100359.GG2258@amd.com>
Date:	Wed, 1 Dec 2010 11:03:59 +0100
From:	"Roedel, Joerg" <Joerg.Roedel@....com>
To:	Nadav Har'El <nyh@...h.technion.ac.il>
CC:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] KVM: Introduce VCPU-wide notion of guest-mode V2

On Wed, Dec 01, 2010 at 03:01:49AM -0500, Nadav Har'El wrote:
> On Mon, Nov 29, 2010, Joerg Roedel wrote about "[PATCH 0/3] KVM: Introduce VCPU-wide notion of guest-mode V2":
> > Hi Avi, Hi Marcelo,
> > 
> > here is the re-spin I promised. The change to V1 are essentially the
> > renames:
> > 
> > 	kvm_vcpu_enter_gm -> enter_guest_mode
> > 	kvm_vcpu_leave_gm -> leave_guest_mode
> > 	kvm_vcpu_is_gm    -> is_guest_mode
> 
> I like this concept, and will be happy to change the nested VMX code to use
> it as well.
> 
> One small thing: After the name change, it might not be obvious on first
> sight that these functions refer to the state of the vcpu, not the state
> of the actual CPU (which, if you think about it, is never in guest mode while
> KVM code is running ;-)). I think that a short comment before the definition
> of these functions might be useful - perhaps saying that they pertain to a
> hypervisor running in the vcpu (i.e., nested virtualization).

Yes, right. Thats a good thing. I sent a follow-on patch adding the
comments.

Btw, another idea which came up recently was to concentrate the actuall
vmexit emulation at a single point. Every code place which does the exit
directly today will be changed to only set a request-bit and the real
exit is then done later. Your code might already do this, I havn't
checked. In fact the idea is from the neste-VMX patchset for Xen :)
This would fit very well in the generic code because it already has
request-bit infrastructure. What do you think, can nested VMX also make
use of that too?

	Joerg

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