[RFC XEN PATCH v4 2/5] x86/pvh: Allow (un)map_pirq when caller isn't DOMID_SELF

[Jiqian Chen <Jiqian.Chen@xxxxxxx>]

If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
a passthrough device by using gsi, see
xen_pt_realize->xc_physdev_map_pirq and
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 domid of the caller is not
DOMID_SELF no matter whether currd has X86_EMU_USE_PIRQ flag
and also allow PHYSDEVOP_unmap_pirq for the failed path to
unmap pirq.

Co-developed-by: Huang Rui <ray.huang@xxxxxxx>
Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
---
 xen/arch/x86/hvm/hypercall.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 6ad5b4d5f11f..632a68be3cc4 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/xen/arch/x86/hvm/hypercall.c
@@ -10,6 +10,7 @@
 #include <xen/hypercall.h>
 #include <xen/ioreq.h>
 #include <xen/nospec.h>
+#include <xen/guest_access.h>
 
 #include <asm/hvm/emulate.h>
 #include <asm/hvm/support.h>
@@ -72,8 +73,30 @@ long hvm_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
arg)
 
     switch ( cmd )
     {
-    case PHYSDEVOP_map_pirq:
-    case PHYSDEVOP_unmap_pirq:
+    case PHYSDEVOP_map_pirq: {
+        physdev_map_pirq_t map;
+
+        if ( copy_from_guest(&map, arg, 1) != 0 )
+            return -EFAULT;
+
+        if ( !has_pirq(currd) && map.domid == DOMID_SELF )
+            return -ENOSYS;
+
+        break;
+    }
+
+    case PHYSDEVOP_unmap_pirq: {
+        physdev_unmap_pirq_t unmap;
+
+        if ( copy_from_guest(&unmap, arg, 1) != 0 )
+            return -EFAULT;
+
+        if ( !has_pirq(currd) && unmap.domid == DOMID_SELF )
+            return -ENOSYS;
+
+        break;
+    }
+
     case PHYSDEVOP_eoi:
     case PHYSDEVOP_irq_status_query:
     case PHYSDEVOP_get_free_pirq:
-- 
2.34.1