> -----Original Message----- > From: Jan Beulich [mailto:jbeul...@suse.com] > Sent: 29 August 2017 10:00 > To: Paul Durrant <paul.durr...@citrix.com> > Cc: Andrew Cooper <andrew.coop...@citrix.com>; George Dunlap > <george.dun...@citrix.com>; Wei Liu <wei.l...@citrix.com>; xen- > de...@lists.xenproject.org > Subject: RE: [Xen-devel] [PATCH v2 REPOST 03/12] x86/mm: add > HYPERVISOR_memory_op to acquire guest resources > > >>> On 29.08.17 at 10:32, <paul.durr...@citrix.com> wrote: > >> From: Wei Liu [mailto:wei.l...@citrix.com] > >> Sent: 28 August 2017 16:01 > >> On Tue, Aug 22, 2017 at 03:50:57PM +0100, Paul Durrant wrote: > >> > + > >> > +/* > >> > + * Get the pages for a particular guest resource, so that they can be > >> > + * mapped directly by a tools domain. > >> > + */ > >> > +#define XENMEM_acquire_resource 28 > >> > +struct xen_mem_acquire_resource { > >> > + /* IN - the domain whose resource is to be mapped */ > >> > + domid_t domid; > >> > + /* IN - the type of resource (defined below) */ > >> > + uint16_t type; > >> > + > >> > +#define XENMEM_resource_grant_table 0 > >> > + > >> > + /* > >> > + * IN - a type-specific resource identifier, which must be zero > >> > + * unless stated otherwise. > >> > + */ > >> > + uint32_t id; > >> > + /* IN - number of (4K) frames of the resource to be mapped */ > >> > + uint32_t nr_frames; > >> > + /* IN - the index of the initial frame to be mapped */ > >> > + uint64_aligned_t frame; > >> > + /* IN/OUT - If the tools domain is PV then, upon return, gmfn_list > >> > + * will be populated with the MFNs of the resource. > >> > + * If the tools domain is HVM then it is expected that, on > >> > + * entry, gmfn_list will be populated with a list of GFNs > >> > + * that will be mapped to the MFNs of the resource. > >> > + */ > >> > + XEN_GUEST_HANDLE(xen_pfn_t) gmfn_list; > >> > >> Why is it not possible to make PV does the same thing as HVM? > > > > Because PV guests don't use a P2M as such. > > They certainly do, just Xen can't rely on (and hence use) it.
Oh I know they have one but, as you say, Xen can't use it do put resources at a particular guest location. > > > An HVM guest can pass GFNs in and > > say 'I want the resource mapped here'. A PV guest can't do that since it's > > using MFNs directly... it has to deal with the resource wherever it may be. > > Xen does, however, maintain the M2P, so it would not be impossible > to return GFNs here for PV guests, requiring the caller to translate > them back to MFNs if so desired. > That's possible, but still different to and HVM caller, which will pass GFNs in rather than using any values returned. So I don't really see any advantage in that. Paul > Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
