x86/pvh: Allow (un)map_pirq when dom0 is PVH

If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
a passthrough device by using gsi, see qemu code
xen_pt_realize->xc_physdev_map_pirq and libxl code
pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq
will call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq
is not allowed because currd is PVH dom0 and PVH has no
X86_EMU_USE_PIRQ flag, it will fail at has_pirq check.

So, allow PHYSDEVOP_map_pirq when dom0 is PVH and also allow
PHYSDEVOP_unmap_pirq for the removal device path to unmap pirq.
And add a new check to prevent (un)map when the subject domain
doesn't have a notion of PIRQ.

So that the interrupt of a passthrough device can be
successfully mapped to pirq for domU with a notion of PIRQ
when dom0 is PVH

Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/x86/hvm/hypercall.c

@@ -71,8 +71,14 @@ long hvm_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
 
     switch ( cmd )
     {
+        /*
+        * Only being permitted for management of other domains.
+        * Further restrictions are enforced in do_physdev_op.
+        */
     case PHYSDEVOP_map_pirq:
     case PHYSDEVOP_unmap_pirq:
+        break;
+
     case PHYSDEVOP_eoi:
     case PHYSDEVOP_irq_status_query:
     case PHYSDEVOP_get_free_pirq:

xen/arch/x86/physdev.c

@@ -323,7 +323,11 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         if ( !d )
             break;
 
-        ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
+        /* Only mapping when the subject domain has a notion of PIRQ */
+        if ( !is_hvm_domain(d) || has_pirq(d) )
+            ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
+        else
+            ret = -EOPNOTSUPP;
 
         rcu_unlock_domain(d);
 
@@ -346,7 +350,11 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         if ( !d )
             break;
 
-        ret = physdev_unmap_pirq(d, unmap.pirq);
+        /* Only unmapping when the subject domain has a notion of PIRQ */
+        if ( !is_hvm_domain(d) || has_pirq(d) )
+            ret = physdev_unmap_pirq(d, unmap.pirq);
+        else
+            ret = -EOPNOTSUPP;
 
         rcu_unlock_domain(d);