From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH RFC V2 5/6] xen,
 libxc: Request page fault injection via libxc
Date: Thu, 17 Jul 2014 13:38:53 +0100
Message-ID: <53C7C3DD.7000105@citrix.com>
References: <1405093418-23481-1-git-send-email-rcojocaru@bitdefender.com>	<1405093418-23481-5-git-send-email-rcojocaru@bitdefender.com>
	<53C027BF.1090902@citrix.com> <53C7BFEA.8040002@bitdefender.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <53C7BFEA.8040002@bitdefender.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: Razvan Cojocaru <rcojocaru@bitdefender.com>, xen-devel@lists.xen.org
Cc: mdontu@bitdefender.com, tim@xen.org, JBeulich@suse.com
List-Id: xen-devel@lists.xenproject.org

On 17/07/14 13:22, Razvan Cojocaru wrote:
> On 07/11/2014 09:06 PM, Andrew Cooper wrote:
>> On 11/07/14 16:43, Razvan Cojocaru wrote:
>>> +         && !ctxt.pending_event
>>> +         && ctxt.cr3 == d->fault_info.address_space )
>>> +    {
>>> +        /* Cache */
>>> +        uint64_t virtual_address = d->fault_info.virtual_address;
>>> +        uint32_t write_access = d->fault_info.write_access;
>>> +
>>> +        /* Reset */
>>> +        d->fault_info.address_space = 0;
>>> +        d->fault_info.virtual_address = 0;
>>> +        d->fault_info.write_access = 0;
>>> +
>>> +        hvm_inject_page_fault((write_access << 1) | PFEC_user_mode,
>> It is sensible in the slightest to have write_access shifted by 1 with
>> respect to a real pagefault error code?
> I'm not sure I follow this comment. Could you please elaborate a bit more?
>
>
> Thanks,
> Razvan Cojocaru

You have a user supplied integer, which you shift left by 1 bit and use
as a pagefault error code.

If it is supposed to be a boolean for read/write only, then it should be
treated as such.  If it is expected to be a full error code, then it
probably shouldn't be shifted.

~Andrew