From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paul Mackerras <paulus@samba.org>
Subject: Re: H_CLEAR_REF and H_CLEAR_MOD
Date: Tue, 14 Apr 2015 21:50:53 +1000
Message-ID: <20150414115053.GA8702@iris.ozlabs.ibm.com>
References: <54E42D5F.9080303@freebsd.org>
 <880391F8-5AD9-4A9A-A868-B8BEB1B1BA92@suse.de>
 <20150218220001.GA24858@iris.ozlabs.ibm.com>
 <54E5214D.40201@freebsd.org>
 <55297CC2.2000206@freebsd.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Alexander Graf <agraf@suse.de>,
	"kvm-ppc@vger.kernel.org" <kvm-ppc@vger.kernel.org>,
	KVM devel mailing list <kvm@vger.kernel.org>
To: Nathan Whitehorn <nwhitehorn@freebsd.org>
Return-path: <kvm-ppc-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <55297CC2.2000206@freebsd.org>
Sender: kvm-ppc-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On Sat, Apr 11, 2015 at 12:57:54PM -0700, Nathan Whitehorn wrote:
> 
> 
> On 02/18/15 15:33, Nathan Whitehorn wrote:
> >
> >On 02/18/15 14:00, Paul Mackerras wrote:
> >>On Wed, Feb 18, 2015 at 09:34:54AM +0100, Alexander Graf wrote:
> >>>>Am 18.02.2015 um 07:12 schrieb Nathan Whitehorn
> >>>><nwhitehorn@freebsd.org>:
> >>>>
> >>>>It seems like KVM doesn't implement the H_CLEAR_REF and H_CLEAR_MOD
> >>>>hypervisor calls, which are absolutely critical for memory
> >>>>management in the FreeBSD kernel (and are marked "mandatory" in the
> >>>>PAPR manual). It seems some patches have been contributed already in https://lists.ozlabs.org/pipermail/linuxppc-dev/2011-December/095013.html,
> >>>>so it would be fantastic if these could end up upstream.
> >>>Paul, I guess we never included this because  there was no user. If
> >>>FreeBSD does use it though, I think it makes a lot of sense to resend
> >>>it for inclusion.
> >>I agree.  I just need to check the locking and synchronization around
> >>the reference and change bit recording, then I'll resend it.
> >
> >Thanks much! Please let me know if I can help at all with this.
> 
> Any news on this? I'm happy to test the patch if you like.
> -Nathan

I have discovered a bug where we can lose the host-side view of the
dirtiness of pages when the guest does a H_CLEAR_MOD on a huge-page
HPTE, so I'm working on a fix for that.

Paul.