From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:57654)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <bharata@linux.vnet.ibm.com>) id 1aLR37-00056Y-Et
	for qemu-devel@nongnu.org; Tue, 19 Jan 2016 02:49:58 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <bharata@linux.vnet.ibm.com>) id 1aLR34-0005uJ-77
	for qemu-devel@nongnu.org; Tue, 19 Jan 2016 02:49:57 -0500
Received: from e28smtp01.in.ibm.com ([125.16.236.1]:41155)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <bharata@linux.vnet.ibm.com>) id 1aLR33-0005tp-HU
	for qemu-devel@nongnu.org; Tue, 19 Jan 2016 02:49:54 -0500
Received: from localhost
	by e28smtp01.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use
	Only! Violators will be prosecuted
	for <qemu-devel@nongnu.org> from <bharata@linux.vnet.ibm.com>;
	Tue, 19 Jan 2016 13:19:49 +0530
Date: Tue, 19 Jan 2016 13:18:17 +0530
From: Bharata B Rao <bharata@linux.vnet.ibm.com>
Message-ID: <20160119074817.GA16048@in.ibm.com>
References: <1453095881-16704-1-git-send-email-david@gibson.dropbear.id.au>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1453095881-16704-1-git-send-email-david@gibson.dropbear.id.au>
Subject: Re: [Qemu-devel] [RFC 0/3] Draft implementation of HPT resizing
	(qemu side)
Reply-To: bharata@linux.vnet.ibm.com
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: lvivier@redhat.com, thuth@redhat.com, qemu-devel@nongnu.org, agraf@suse.de, qemu-ppc@nongnu.org, paulus@samba.org

On Mon, Jan 18, 2016 at 04:44:38PM +1100, David Gibson wrote:
> Here is a draft qemu implementation of my proposed PAPR extension for
> allowing runtime resizing of a KVM/ppc64 guest's hash page table.
> That in turn will allow for more flexible memory hotplug.
> 
> This should work with the guest kernel side patches I also posted
> recently [1].
> 
> Still required to make this into a full implementation:
>   * Guest needs to auto-resize HPT on memory hotplug events
> 
>   * qemu needs to allocate HPT size based on current rather than
>     maximum memory if the guest is HPT resize aware
> 
>   * KVM host side implementation
> 
>   * PAPR standardization

So with the current patchset (QEMU and guest kernel changes), I should
be able to change the HTAB size of a PR guest right ? I see the below
failure though:

[root@localhost ~]# cat /sys/kernel/debug/powerpc/pft-size 
24
[root@localhost ~]# echo 26 > /sys/kernel/debug/powerpc/pft-size
[   65.996845] lpar: Attempting to resize HPT to shift 26
[   65.996845] lpar: Attempting to resize HPT to shift 26
[   66.113596] lpar: HPT resize to shift 26 complete (109 ms / 6 ms)
[   66.113596] lpar: HPT resize to shift 26 complete (109 ms / 6 ms)

PR guest just hangs here while I see tons of below messages in
the 1st level guest:

KVM can't copy data from 0x3fff99e91400!
...
Couldn't emulate instruction 0x00000000 (op 0 xop 0)
kvmppc_handle_exit_pr: emulation at 700 failed (00000000)

Regards,
Bharata.