[PATCH v2] libxc: add xc_domain_remove_from_physmap to wrap XENMEM_remove_from_physmap

[Zhongze Liu <blackskygg@gmail.com>]

This is for the proposal "Allow setting up shared memory areas between VMs
from xl config file". See:

  https://lists.xenproject.org/archives/html/xen-devel/2017-07/msg03047.html

Then plan is to use XENMEM_add_to_physmap_batch to map the shared pages from
one domU to another and use XENMEM_remove_from_physmap to cancel the sharing.
A wrapper to XENMEM_add_to_physmap_batch was added in the following commit:

  commit 20e725e9364cff4a29945f66986ecd88cca8743d

Now add the wrapper to XENMEM_remove_from_physmap.

Signed-off-by: Zhongze Liu <blackskygg@gmail.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Julien Grall <julien.grall@arm.com>
Cc: xen-devel@lists.xen.org
---
  v2: add the signed-off message
---
 tools/libxc/include/xenctrl.h |  4 ++++
 tools/libxc/xc_domain.c       | 11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index c7710b8f36..0ff15a9255 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -1381,6 +1381,10 @@ int xc_domain_add_to_physmap_batch(xc_interface *xch,
                                    xen_pfn_t *gfpns,
                                    int *errs);
 
+int xc_domain_remove_from_physmap(xc_interface *xch,
+                                  domid_t domid,
+                                  xen_pfn_t gpfn);
+
 int xc_domain_populate_physmap(xc_interface *xch,
                                uint32_t domid,
                                unsigned long nr_extents,
diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
index 3bab4e8bab..e6b32792c0 100644
--- a/tools/libxc/xc_domain.c
+++ b/tools/libxc/xc_domain.c
@@ -1077,6 +1077,17 @@ out:
     return rc;
 }
 
+int xc_domain_remove_from_physmap(xc_interface *xch,
+                                  domid_t domid,
+                                  xen_pfn_t gpfn)
+{
+    struct xen_remove_from_physmap xrfp = {
+        .domid = domid,
+        .gpfn = gpfn,
+    };
+    return do_memory_op(xch, XENMEM_remove_from_physmap, &xrfp, sizeof(xrfp));
+}
+
 int xc_domain_claim_pages(xc_interface *xch,
                                uint32_t domid,
                                unsigned long nr_pages)
-- 
2.14.0


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