xen/privcmd: improve performance of MMAPBATCH_V2

Make the IOCTL_PRIVCMD_MMAPBATCH_V2 (and older V1 version) map
multiple frames at a time rather than one at a time, despite the pages
being non-consecutive GFNs.

xen_remap_foreign_mfn_array() is added which maps an array of GFNs
(instead of a consecutive range of GFNs).

Since per-frame errors are returned in an array, privcmd must set the
MMAPBATCH_V1 error bits as part of the "report errors" phase, after
all the frames are mapped.

Migrate times are significantly improved (when using a PV toolstack
domain).  For example, for an idle 12 GiB PV guest:

        Before     After
  real  0m38.179s  0m26.868s
  user  0m15.096s  0m13.652s
  sys   0m28.988s  0m18.732s

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

1 files changed, 41 insertions, 4 deletions

diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index 9eb88a4512bd..c643e6a94c9a 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -27,17 +27,54 @@ int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
 void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order);
 
 struct vm_area_struct;
+
+/*
+ * xen_remap_domain_mfn_array() - map an array of foreign frames
+ * @vma:     VMA to map the pages into
+ * @addr:    Address at which to map the pages
+ * @gfn:     Array of GFNs to map
+ * @nr:      Number entries in the GFN array
+ * @err_ptr: Returns per-GFN error status.
+ * @prot:    page protection mask
+ * @domid:   Domain owning the pages
+ * @pages:   Array of pages if this domain has an auto-translated physmap
+ *
+ * @gfn and @err_ptr may point to the same buffer, the GFNs will be
+ * overwritten by the error codes after they are mapped.
+ *
+ * Returns the number of successfully mapped frames, or a -ve error
+ * code.
+ */
+int xen_remap_domain_mfn_array(struct vm_area_struct *vma,
+                               unsigned long addr,
+                               xen_pfn_t *gfn, int nr,
+                               int *err_ptr, pgprot_t prot,
+                               unsigned domid,
+                               struct page **pages);
+
+/* xen_remap_domain_mfn_range() - map a range of foreign frames
+ * @vma:     VMA to map the pages into
+ * @addr:    Address at which to map the pages
+ * @gfn:     First GFN to map.
+ * @nr:      Number frames to map
+ * @prot:    page protection mask
+ * @domid:   Domain owning the pages
+ * @pages:   Array of pages if this domain has an auto-translated physmap
+ *
+ * Returns the number of successfully mapped frames, or a -ve error
+ * code.
+ */
 int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
                                unsigned long addr,
-                               xen_pfn_t mfn, int nr,
+                               xen_pfn_t gfn, int nr,
                                pgprot_t prot, unsigned domid,
                                struct page **pages);
 int xen_unmap_domain_mfn_range(struct vm_area_struct *vma,
                                int numpgs, struct page **pages);
-int xen_xlate_remap_gfn_range(struct vm_area_struct *vma,
+int xen_xlate_remap_gfn_array(struct vm_area_struct *vma,
                               unsigned long addr,
-                              xen_pfn_t gfn, int nr,
-                              pgprot_t prot,
+                              xen_pfn_t *gfn, int nr,
+                              int *err_ptr, pgprot_t prot,
                               unsigned domid,
                               struct page **pages);
 int xen_xlate_unmap_gfn_range(struct vm_area_struct *vma,