From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH] libxc: introduce a per architecture scratch pfn for temporary grant mapping Date: Wed, 14 Jan 2015 13:31:00 +0000 Message-ID: <1421242260.19103.258.camel@citrix.com> References: <1421179848-31833-1-git-send-email-julien.grall@linaro.org> <54B66805.4080902@citrix.com> <54B66D29.6050001@linaro.org> <54B66DEA.4010105@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YBO2o-0004Qp-1Y for xen-devel@lists.xenproject.org; Wed, 14 Jan 2015 13:31:34 +0000 In-Reply-To: <54B66DEA.4010105@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper Cc: Wei Liu , Stefano Stabellini , Julien Grall , Ian Jackson , Jan Beulich , xen-devel@lists.xenproject.org, Roger Pau =?ISO-8859-1?Q?Monn=E9?= List-Id: xen-devel@lists.xenproject.org On Wed, 2015-01-14 at 13:23 +0000, Andrew Cooper wrote: > > ARM is defining a grant table range which is out of the RAM and not > > mapped at that time. So we can reuse it with any possible issue. > > Do you mean to say that there is a grant table range baked into the ABI > occupying guest physical address space? A range of otherwise unused IPA space is suggested to the guest via the device tree node, as a convenience for the guest so it doesn't need to figure one out for itself (it's morally equivalent to the BAR provided on the x86 platform PCI device). So the actual address is not part of the guest ABI, but the toolstack does know what it is going to be since it is privy to some internal details of the guest layout. Ian.