From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH 01/18] xen: reinstate previously unused XENMEM_remove_from_physmap hypercall Date: Thu, 19 Jan 2012 10:32:28 +0000 Message-ID: <1326969148.17599.41.camel@zakaz.uk.xensource.com> References: <1326302490-19428-1-git-send-email-dgdegra@tycho.nsa.gov> <1326411330-7915-1-git-send-email-dgdegra@tycho.nsa.gov> <1326411330-7915-2-git-send-email-dgdegra@tycho.nsa.gov> <1326882968.14689.176.camel@zakaz.uk.xensource.com> <4F16DD96.6080304@tycho.nsa.gov> <1326902794.14689.243.camel@zakaz.uk.xensource.com> <4F17187B.2050102@tycho.nsa.gov> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4F17187B.2050102@tycho.nsa.gov> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Daniel De Graaf Cc: "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On Wed, 2012-01-18 at 19:07 +0000, Daniel De Graaf wrote: > On 01/18/2012 11:06 AM, Ian Campbell wrote: > > On Wed, 2012-01-18 at 14:56 +0000, Daniel De Graaf wrote: > >> On 01/18/2012 05:36 AM, Ian Campbell wrote: > >>> On Thu, 2012-01-12 at 23:35 +0000, Daniel De Graaf wrote: > >>>> From: Alex Zeffertt > >>>> > >>>> This patch reinstates the XENMEM_remove_from_physmap hypercall > >>>> which was removed in 19041:ee62aaafff46 because it was not used. > >>>> > >>>> However, is now needed in order to support xenstored stub domains. > >>>> The xenstored stub domain is not priviliged like dom0 and so cannot > >>>> unilaterally map the xenbus page of other guests into it's address > >>>> space. Therefore, before creating a domU the domain builder needs to > >>>> seed its grant table with a grant ref allowing the xenstored stub > >>>> domain to access the new domU's xenbus page. > >>>> > >>>> At present domU's do not start with their grant table mapped. > >>>> Instead it gets mapped when the guest requests a grant table from > >>>> the hypervisor. > >>>> > >>>> In order to seed the grant table, the domain builder first needs to > >>>> map it into dom0 address space. But the hypercall to do this > >>>> requires a gpfn (guest pfn), which is an mfn for PV guest, but a pfn > >>>> for HVM guests. Therfore, in order to seed the grant table of an > >>>> HVM guest, dom0 needs to *temporarily* map it into the guest's > >>>> "physical" address space. > >>>> > >>>> Hence the need to reinstate the XENMEM_remove_from_physmap hypercall. > >>>> > >>>> Signed-off-by: Alex Zeffertt > >>>> Signed-off-by: Daniel De Graaf > >>> > >>> Acked-by: Ian Campbell (modulo Jan's comment > >>> about ordering in xlat.lst) > >>> > >>> BTW, since Alex and Diego have subsequently left Citrix you could take > >>> my Acked-by's in this series as Signed-of-by on behalf of Citrix. I've > >>> no idea if that's necessary though, I expect not. > >>> > >>> Ian. > >>> > >> > >> I'm not an expert in this area, > > > > Me neither. > > > >> but this is how I read it: the portion of > >> the path authored by Alex/Diego was already signed-off when they were posted, > >> so since the current patches are derived works from them the sign-off may > >> need to stay in order to allow me to sign off because I cannot claim copyright > >> on all of the content. Assuming Citrix actually owns the copyright on the > >> patches, your Ack may suffice to replace the sign-off for this purpose. > > > > I don't think an Ack conveys the same meaning (WRT the DCO) as a > > Signed-off-by. > > > >> I guess my real question here would be: should the sign-off from Alex and > >> Diego remain on these patches in addition to your Ack? > > > > I would suggest you keep any signed-off-by they provided and augment it > > with my ack. > > > > I think I saw one or two which said "Originally-by" instead of > > "Signed-of-by", I guess those were either missing a Signed-off-by in the > > first place or have been heavily modified? > > > > Ian. > > > > I originally replaced all the signed-off-by lines with originally-by and > missed one when converting back. When looking at the Linux version of the > DCO, it implies (lower down when talking about subsystem maintainers) that > if I make changes I need to drop the sign-off and claim clause (b) unless > the original author is around to sign-off on the changed patch, or if it is > trivial and I note this above my sign-off (not applicable here). This makes > me lean toward changing back to "Originally-by" or similar tags. I did keep > the From tags for those patches that I did not mostly rewrite, which I assume > will be recognized when importing patches. The DCO itself isn't terribly specific about what to do with an existing Signed-off-by if you modify the patch. Common practice appears to be to include both the original and your own and to note what you have changed unless you have done a wholesale rewrite in which case it is "Based-on"/"Originally-by"/etc + your own S-o-b. Ian. >