[PATCH 3/3] hvm/pirq: allow control domains usage of PHYSDEVOP_{un,}map_pirq

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Control domains (including domains having control over a single other
guest) need access to PHYSDEVOP_{un,}map_pirq in order to setup
bindings of interrupts from devices assigned to the controlled guest.

As such relax the check for HVM based guests and allow the usage of
the hypercalls for any control domains. Note that further safety
checks will be performed in order to assert that the current domain
has the right permissions against the target of the hypercall.

Reported-by: Alex Olson <this.is.a0lson@xxxxxxxxx>
Reported-by: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/hvm/hypercall.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 030243810e..9128e4d025 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/xen/arch/x86/hvm/hypercall.c
@@ -87,6 +87,13 @@ static long hvm_physdev_op(int cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
     {
     case PHYSDEVOP_map_pirq:
     case PHYSDEVOP_unmap_pirq:
+        /*
+         * Control domain (and domains controlling others) need to use
+         * PHYSDEVOP_{un,}map_pirq in order to setup interrupts for passthrough
+         * devices on behalf of other guests.
+         */
+        if ( is_control_domain(currd) || currd->target )
+            break;
     case PHYSDEVOP_eoi:
     case PHYSDEVOP_irq_status_query:
     case PHYSDEVOP_get_free_pirq:
-- 
2.34.1