From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com>
Subject: Re: [PATCH 2/3] amd-iommu: disable iommu_hap_pt_share
	with AMD IOMMUs
Date: Tue, 8 Apr 2014 17:39:08 +0200
Message-ID: <5344181C.3060103@citrix.com>
References: <1396886524-16921-1-git-send-email-roger.pau@citrix.com>
	<1396886524-16921-3-git-send-email-roger.pau@citrix.com>
	<5343D4FC0200007800006788@nat28.tlf.novell.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta5.messagelabs.com ([195.245.231.135])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <roger.pau@citrix.com>) id 1WXY95-0002q6-2f
	for xen-devel@lists.xenproject.org; Tue, 08 Apr 2014 15:41:07 +0000
In-Reply-To: <5343D4FC0200007800006788@nat28.tlf.novell.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel@lists.xenproject.org, Tim Deegan <tim@xen.org>, Xiantao Zhang <xiantao.zhang@intel.com>, Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
List-Id: xen-devel@lists.xenproject.org

On 08/04/14 10:52, Jan Beulich wrote:
>>>> On 07.04.14 at 18:02, <roger.pau@citrix.com> wrote:
>> --- a/xen/drivers/passthrough/amd/iommu_init.c
>> +++ b/xen/drivers/passthrough/amd/iommu_init.c
>> @@ -1255,6 +1255,13 @@ int __init amd_iommu_init(void)
>>      if ( iterate_ivrs_mappings(amd_iommu_setup_device_table) != 0 )
>>          goto error_out;
>>  
>> +    /*
>> +     * Disable sharing HAP page tables with AMD IOMMU,
>> +     * since it only supports p2m_ram_rw, and this would
>> +     * prevent doing IO to/from mapped grant frames.
>> +     */
>> +    iommu_hap_pt_share = 0;
>> +
> 
> I guess at the very least when the option was specified on the
> command line you should issue a warning, or perhaps even stay
> away from enforcing this.

I think we should enforce it even if the user has specified
sharept=true, or else we need to gate the
XENFEAT_hvm_gntmap_supports_iommu feature. Printing a Warning in this
case (user trying to enforce sharept on AMD IOMMU) seems OK to me.

Roger.