[XEN PATCH v11 2/8] x86/pvh: Allow (un)map_pirq when dom0 is PVH

[Jiqian Chen]

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
has no X86_EMU_USE_PIRQ flag.

So that the interrupt of a passthrough device can be
successfully mapped to pirq for domU with X86_EMU_USE_PIRQ flag
when dom0 is PVH

Signed-off-by: Jiqian Chen <jiqian.c...@amd.com>
Signed-off-by: Huang Rui <ray.hu...@amd.com>
Signed-off-by: Jiqian Chen <jiqian.c...@amd.com>
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
---
 xen/arch/x86/hvm/hypercall.c |  6 ++++++
 xen/arch/x86/physdev.c       | 14 ++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 0fab670a4871..03ada3c880bd 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/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:
diff --git a/xen/arch/x86/physdev.c b/xen/arch/x86/physdev.c
index d6dd622952a9..a165f68225c1 100644
--- a/xen/arch/x86/physdev.c
+++ b/xen/arch/x86/physdev.c
@@ -323,6 +323,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
arg)
         if ( !d )
             break;
 
+        /* Prevent mapping when the subject domain has no X86_EMU_USE_PIRQ */
+        if ( is_hvm_domain(d) && !has_pirq(d) )
+        {
+            rcu_unlock_domain(d);
+            return -EOPNOTSUPP;
+        }
+
         ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
 
         rcu_unlock_domain(d);
@@ -346,6 +353,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
arg)
         if ( !d )
             break;
 
+        /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
+        if ( is_hvm_domain(d) && !has_pirq(d) )
+        {
+            rcu_unlock_domain(d);
+            return -EOPNOTSUPP;
+        }
+
         ret = physdev_unmap_pirq(d, unmap.pirq);
 
         rcu_unlock_domain(d);
-- 
2.34.1