From: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
Grant unmap removes the grant from maptrack and marks it as not in use.
We maintain a one-to-one correspondence between grant table and maptrack
entries so there's no contention in allocation/free.
Co-developed-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
---
arch/x86/kvm/xen.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 73 insertions(+)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 3603645086a7..8f06924e0dfa 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1684,6 +1684,69 @@ static int shim_hcall_gntmap(struct kvm_xen *ld,
return 0;
}
+static int shim_hcall_gntunmap(struct kvm_xen *xen,
+ struct gnttab_unmap_grant_ref *op)
+{
+ struct kvm_grant_map *map, unmap;
+ struct grant_entry_v1 **rgt;
+ struct grant_entry_v1 *shah;
+ struct kvm *rd = NULL;
+ domid_t domid;
+ u32 ref;
+
+ domid = handle_get_domid(op->handle);
+ ref = handle_get_grant(op->handle);
+
+
+ rd = kvm_xen_find_vm(domid);
+ if (unlikely(!rd)) {
+ /* We already teardown all ongoing grant maps */
+ op->status = GNTST_okay;
+ return 0;
+ }
+
+ if (unlikely(ref >= gnttab_entries(rd))) {
+ pr_err("gnttab: bad ref %u\n", ref);
+ op->status = GNTST_bad_handle;
+ return 0;
+ }
+
+ rgt = rd->arch.xen.gnttab.frames_v1;
+ map = maptrack_entry(rd->arch.xen.gnttab.handle, ref);
+
+ /*
+ * The test_and_clear_bit (below) serializes ownership of this
+ * grant-entry. After we clear it, there can be a grant-map on this
+ * entry. So we cache the unmap entry before relinquishing ownership.
+ */
+ unmap = *map;
+
+ if (!test_and_clear_bit(_KVM_GNTMAP_ACTIVE,
+ (unsigned long *) &map->flags)) {
+ pr_err("gnttab: bad flags for %u (dom %u ref %u) flags %x\n",
+ op->handle, domid, ref, unmap.flags);
+ op->status = GNTST_bad_handle;
+ return 0;
+ }
+
+ /* Give up the reference taken in get_user_pages_remote(). */
+ put_page(virt_to_page(unmap.gpa));
+
+ shah = shared_entry(rgt, unmap.ref);
+
+ /*
+ * We have cleared _KVM_GNTMAP_ACTIVE, so a simultaneous grant-map
+ * could update the shah and we would stomp all over it but the
+ * guest deserves it.
+ */
+ if (!(unmap.flags & GNTMAP_readonly))
+ clear_bit(_GTF_writing, (unsigned long *) &shah->flags);
+ clear_bit(_GTF_reading, (unsigned long *) &shah->flags);
+
+ op->status = GNTST_okay;
+ return 0;
+}
+
static int shim_hcall_gnttab(int op, void *p, int count)
{
int ret = -ENOSYS;
@@ -1698,6 +1761,16 @@ static int shim_hcall_gnttab(int op, void *p, int count)
ret = 0;
break;
}
+ case GNTTABOP_unmap_grant_ref: {
+ struct gnttab_unmap_grant_ref *ref = p;
+
+ for (i = 0; i < count; i++) {
+ shim_hcall_gntunmap(xen_shim, ref + i);
+ ref[i].host_addr = 0;
+ }
+ ret = 0;
+ break;
+ }
default:
pr_info("lcall-gnttab:op default=%d\n", op);
break;
--
2.11.0
