Mailing List Archive

xen/arch/x86/mm/mem_sharing.c | 106 ++++++++++++++++++++++++++++++++++++++++++
xen/include/public/domctl.h | 3 +-
2 files changed, 108 insertions(+), 1 deletions(-)


This domctl is useful to, for example, populate parts of a domain's
physmap with shared frames, directly.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>

diff -r 62ea5c05ae7b -r b8be3a08e628 xen/arch/x86/mm/mem_sharing.c
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -734,6 +734,76 @@ err_out:
return ret;
}

+int mem_sharing_add_to_physmap(struct domain *sd, unsigned long sgfn, shr_handle_t sh,
+ struct domain *cd, unsigned long cgfn)
+{
+ struct page_info *spage;
+ int ret = -EINVAL;
+ mfn_t smfn, cmfn;
+ p2m_type_t smfn_type, cmfn_type;
+ struct gfn_info *gfn_info;
+ struct p2m_domain *p2m = p2m_get_hostp2m(cd);
+ p2m_access_t a;
+
+ shr_lock();
+ p2m_lock(p2m);
+
+ /* XXX if sd == cd handle potential deadlock by ordering
+ * the get_ and put_gfn's */
+ smfn = get_gfn_query(sd, sgfn, &smfn_type);
+ cmfn = get_gfn_type_access(p2m, cgfn, &cmfn_type, &a, p2m_query, NULL);
+
+ /* Get the source shared page, check and lock */
+ ret = XEN_DOMCTL_MEM_SHARING_S_HANDLE_INVALID;
+ spage = __grab_shared_page(smfn);
+ if ( spage == NULL )
+ goto err_out;
+ ASSERT(smfn_type == p2m_ram_shared);
+
+ /* Check that the handles match */
+ if ( spage->shared_info->handle != sh )
+ goto err_unlock;
+
+ /* Make sure the target page is a hole in the physmap */
+ if ( mfn_valid(cmfn) ||
+ (!(p2m_is_ram(cmfn_type))) )
+ {
+ ret = XEN_DOMCTL_MEM_SHARING_C_HANDLE_INVALID;
+ goto err_unlock;
+ }
+
+ /* This is simpler than regular sharing */
+ BUG_ON(!get_page_and_type(spage, dom_cow, PGT_shared_page));
+ if ( (gfn_info = mem_sharing_gfn_alloc(spage, cd, cgfn)) == NULL )
+ {
+ put_page_and_type(spage);
+ ret = -ENOMEM;
+ goto err_unlock;
+ }
+
+ ret = set_p2m_entry(p2m, cgfn, smfn, PAGE_ORDER_4K, p2m_ram_shared, a);
+
+ /* Tempted to turn this into an assert */
+ if ( !ret ) {
+ ret = -ENOENT;
+ mem_sharing_gfn_destroy(gfn_info, 0);
+ put_page_and_type(spage);
+ } else {
+ atomic_inc(&cd->shr_pages);
+ atomic_inc(&nr_shared_mfns);
+ ret = 0;
+ }
+
+err_unlock:
+ mem_sharing_page_unlock(spage);
+err_out:
+ put_gfn(cd, cgfn);
+ put_gfn(sd, sgfn);
+ p2m_unlock(p2m);
+ shr_unlock();
+ return ret;
+}
+
int mem_sharing_unshare_page(struct domain *d,
unsigned long gfn,
uint16_t flags)
@@ -982,6 +1052,42 @@ int mem_sharing_domctl(struct domain *d,
}
break;

+ case XEN_DOMCTL_MEM_EVENT_OP_SHARING_ADD_PHYSMAP:
+ {
+ unsigned long sgfn, cgfn;
+ struct domain *cd;
+ shr_handle_t sh;
+
+ if ( !mem_sharing_enabled(d) )
+ return -EINVAL;
+
+ cd = get_domain_by_id(mec->u.share.client_domain);
+ if ( !cd )
+ return -ESRCH;
+
+ if ( !mem_sharing_enabled(cd) )
+ {
+ put_domain(cd);
+ return -EINVAL;
+ }
+
+ if ( XEN_DOMCTL_MEM_SHARING_FIELD_IS_GREF(mec->u.share.source_gfn) )
+ {
+ /* Cannot add a gref to the physmap */
+ put_domain(cd);
+ return -EINVAL;
+ }
+
+ sgfn = mec->u.share.source_gfn;
+ sh = mec->u.share.source_handle;
+ cgfn = mec->u.share.client_gfn;
+
+ rc = mem_sharing_add_to_physmap(d, sgfn, sh, cd, cgfn);
+
+ put_domain(cd);
+ }
+ break;
+
case XEN_DOMCTL_MEM_EVENT_OP_SHARING_RESUME:
{
if ( !mem_sharing_enabled(d) )
diff -r 62ea5c05ae7b -r b8be3a08e628 xen/include/public/domctl.h
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -771,6 +771,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_domctl_mem_e
#define XEN_DOMCTL_MEM_EVENT_OP_SHARING_DEBUG_GFN 5
#define XEN_DOMCTL_MEM_EVENT_OP_SHARING_DEBUG_MFN 6
#define XEN_DOMCTL_MEM_EVENT_OP_SHARING_DEBUG_GREF 7
+#define XEN_DOMCTL_MEM_EVENT_OP_SHARING_ADD_PHYSMAP 8

#define XEN_DOMCTL_MEM_SHARING_S_HANDLE_INVALID (-10)
#define XEN_DOMCTL_MEM_SHARING_C_HANDLE_INVALID (-9)
@@ -797,7 +798,7 @@ struct xen_domctl_mem_sharing_op {
} u;
uint64_aligned_t handle; /* OUT: the handle */
} nominate;
- struct mem_sharing_op_share { /* OP_SHARE */
+ struct mem_sharing_op_share { /* OP_SHARE/ADD_PHYSMAP */
uint64_aligned_t source_gfn; /* IN: the gfn of the source page */
uint64_aligned_t source_handle; /* IN: handle to the source page */
uint64_aligned_t client_domain; /* IN: the client domain id */

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