On Mon, Apr 25, 2016 at 3:19 PM, Paul Durrant <paul.durr...@citrix.com> wrote: >> -----Original Message----- >> From: Jan Beulich [mailto:jbeul...@suse.com] >> Sent: 25 April 2016 15:16 >> To: Paul Durrant >> Cc: Andrew Cooper; George Dunlap; Wei Liu; Jun Nakajima; Kevin Tian; >> Zhiyuan Lv; Yu Zhang; xen-devel@lists.xen.org; Keir (Xen.org); Tim (Xen.org) >> Subject: RE: [Xen-devel] [PATCH v3 1/3] x86/ioreq server(patch for 4.7): >> Rename p2m_mmio_write_dm to p2m_ioreq_server. >> >> >>> On 25.04.16 at 16:01, <paul.durr...@citrix.com> wrote: >> > The p2m type changes are also wrong. That type needs to be left alone, >> > presumably, so that anything using HVMMEM_mmio_write_dm and >> compiled to the >> > old interface version continues to function. I think HVMMEM_ioreq_server >> > needs to map to a new p2m type which should be introduced in patch #3. >> >> I don't understand this part: I thought it was agreed that the old >> p2m type needs to go away (not the least because we're tight on >> these), and use of the old HVMMEM_* type needs to result in >> errors. >> > > I may have misunderstood. I thought we'd back-tracked on that because there's > a concern that we also need to keep anything compiled against the old header > working. If not then this patch should also remove that p2m type, not rename > it.
You mean remove the old HVMMEM type? There are two issues: 1. Whether old code should continue to compile 2. How old code should act on new hypervisors I think we've determined that we definitely cannot allow code compiled against old hypervisors to accidentally use a different p2m type; so we certainly need to "burn" an enum here. I'd personally prefer we just straight-up rename it to HVMMEM_unused, so nobody continues to think that the HVMMEM_mmio_write_dm functionality might still actually work; I think Jan thinks that's not allowed. Honestly I don't see the point of letting it compile and then return -EINVAL when we run it. If people complain that it doesn't work anymore we should either make it compile *and* maintain the functionality, or say "Sorry, just use an older version" and make it neither compile nor maintain the functionality. But I sort of assumed this discussion on what support looked like had already been had and Jan was just enforcing it. (Maybe we should have had a talk about this in person at the Hackathon...) -George _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
