> -----Original Message----- > From: Jan Beulich [mailto:jbeul...@suse.com] > Sent: 25 September 2017 15:23 > To: Paul Durrant <paul.durr...@citrix.com> > Cc: Andrew Cooper <andrew.coop...@citrix.com>; xen- > de...@lists.xenproject.org > Subject: Re: [PATCH v7 02/12] x86/mm: add HYPERVISOR_memory_op to > acquire guest resources > > >>> On 18.09.17 at 17:31, <paul.durr...@citrix.com> wrote: > > Certain memory resources associated with a guest are not necessarily > > present in the guest P2M and so are not necessarily available to be > > foreign-mapped by a tools domain unless they are inserted, which risks > > shattering a super-page mapping. > > Btw., I'm additionally having trouble seeing this shattering of a > superpage: For one, xc_core_arch_get_scratch_gpfn() could be > a little less simplistic. And then even with the currently chosen > value (outside of the range of valid GFNs at that point in time) > there shouldn't be a larger page to be shattered, as there should > be no mapping at all at that index. But perhaps I'm just blind and > don't see the obvious ...
The shattering was Andrew's observation. Andrew, can you comment? Even if it's not the case, it's suboptimal to have to write-lock and update the guest's P2M twice just to map a page of grants, which I will mention in the commit comment too. Paul > > Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
