From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Vrabel <david.vrabel@citrix.com>
Subject: Re: [PATCHv4 04/14] xen: remove scratch frames for
 ballooned pages and m2p override
Date: Tue, 27 Jan 2015 11:00:39 +0000
Message-ID: <54C76FD7.6070701@citrix.com>
References: <1422291687-7398-1-git-send-email-david.vrabel@citrix.com>
	<1422291687-7398-5-git-send-email-david.vrabel@citrix.com>
	<alpine.DEB.2.02.1501271055010.9702@kaball.uk.xensource.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.bemta3.messagelabs.com ([195.245.230.39])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <david.vrabel@citrix.com>) id 1YG3sy-0004aI-Qr
	for xen-devel@lists.xenproject.org; Tue, 27 Jan 2015 11:00:44 +0000
In-Reply-To: <alpine.DEB.2.02.1501271055010.9702@kaball.uk.xensource.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: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: xen-devel@lists.xenproject.org, Boris Ostrovsky <boris.ostrovsky@oracle.com>
List-Id: xen-devel@lists.xenproject.org

On 27/01/15 10:57, Stefano Stabellini wrote:
> On Mon, 26 Jan 2015, David Vrabel wrote:
>> The scratch frame mappings for ballooned pages and the m2p override
>> are broken.  Remove them in preparation for replacing them with
>> simpler mechanisms that works.
>>
>> The scratch pages did not ensure that the page was not in use.  In
>> particular, the foreign page could still be in use by hardware.  If
>> the guest reused the frame the hardware could read or write that
>> frame.
>>
>> The m2p override did not handle the same frame being granted by two
>> different grant references.  Trying an M2P override lookup in this
>> case is impossible.
>>
>> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> 
> [...]
> 
>>  int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
>>  			    struct gnttab_map_grant_ref *kmap_ops,
>>  			    struct page **pages, unsigned int count)
>>  {
>>  	int i, ret = 0;
>> -	bool lazy = false;
>>  	pte_t *pte;
>>  
>>  	if (xen_feature(XENFEAT_auto_translated_physmap))
>>  		return 0;
>>  
>> -	if (kmap_ops &&
>> -	    !in_interrupt() &&
>> -	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
>> -		arch_enter_lazy_mmu_mode();
>> -		lazy = true;
>> +	if (kmap_ops) {
>> +		ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
>> +						kmap_ops, count);
>> +		if (ret)
>> +			goto out;
>>  	}
> 
> I think that you should explain why you are adding one more grant table
> mapping to a function meant to work on the p2m/m2p.  Everything else is
> clear.

I'm not.  This function has always done this.

David