[XEN PATCH v10 2/5] 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 failed path to unmap pirq. And
add a new check to prevent self map when subject domain has no
PIRQ flag.

So that domU with PIRQ flag can success to map pirq for
passthrough devices even dom0 has no PIRQ flag.

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..f38cc22c872e 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 self-map when currd has no X86_EMU_USE_PIRQ flag */
+        if ( is_hvm_domain(d) && !has_pirq(d) && d == currd )
+        {
+            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 self-unmap when currd has no X86_EMU_USE_PIRQ flag */
+        if ( is_hvm_domain(d) && !has_pirq(d) && d == currd )
+        {
+            rcu_unlock_domain(d);
+            return -EOPNOTSUPP;
+        }
+
         ret = physdev_unmap_pirq(d, unmap.pirq);
 
         rcu_unlock_domain(d);
-- 
2.34.1