Messages in this thread | | | Subject | Re: [RFC PATCH 16/16] xen/grant-table: host_addr fixup in mapping on xenhost_r0 | From | Juergen Gross <> | Date | Mon, 17 Jun 2019 12:55:59 +0200 |
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On 09.05.19 19:25, Ankur Arora wrote: > Xenhost type xenhost_r0 does not support standard GNTTABOP_map_grant_ref > semantics (map a gref onto a specified host_addr). That's because > since the hypervisor is local (same address space as the caller of > GNTTABOP_map_grant_ref), there is no external entity that could > map an arbitrary page underneath an arbitrary address. > > To handle this, the GNTTABOP_map_grant_ref hypercall on xenhost_r0 > treats the host_addr as an OUT parameter instead of IN and expects the > gnttab_map_refs() and similar to fixup any state that caches the > value of host_addr from before the hypercall. > > Accordingly gnttab_map_refs() now adds two parameters, a fixup function > and a pointer to cached maps to fixup: > int gnttab_map_refs(xenhost_t *xh, struct gnttab_map_grant_ref *map_ops, > struct gnttab_map_grant_ref *kmap_ops, > - struct page **pages, unsigned int count) > + struct page **pages, gnttab_map_fixup_t map_fixup_fn, > + void **map_fixup[], unsigned int count) > > The reason we use a fixup function and not an additional mapping op > in the xenhost_t is because, depending on the caller, what we are fixing > might be different: blkback, netback for instance cache host_addr in > via a struct page *, while __xenbus_map_ring() caches a phys_addr. > > This patch fixes up xen-blkback and xen-gntdev drivers. > > TODO: > - also rewrite gnttab_batch_map() and __xenbus_map_ring(). > - modify xen-netback, scsiback, pciback etc > > Co-developed-by: Joao Martins <joao.m.martins@oracle.com> > Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Without seeing the __xenbus_map_ring() modification it is impossible to do a proper review of this patch.
Juergen
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