[Xen-devel] [PATCH v8 22/27] ARM: vITS: handle DISCARD command

[Andre Przywara <andre.przywara@xxxxxxx>]

The DISCARD command drops the connection between a DeviceID/EventID
and an LPI/collection pair.
We mark the respective structure entries as not allocated and make
sure that any queued IRQs are removed.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
 xen/arch/arm/vgic-v3-its.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
index be9de08..09cb3af 100644
--- a/xen/arch/arm/vgic-v3-its.c
+++ b/xen/arch/arm/vgic-v3-its.c
@@ -276,9 +276,9 @@ static bool read_itte(struct virt_its *its, uint32_t devid, 
uint32_t evid,
  * If vcpu_ptr is provided, returns the VCPU belonging to that collection.
  * Must be called with the ITS lock held.
  */
-bool write_itte_locked(struct virt_its *its, uint32_t devid,
-                       uint32_t evid, uint32_t collid, uint32_t vlpi,
-                       struct vcpu **vcpu_ptr)
+static bool write_itte_locked(struct virt_its *its, uint32_t devid,
+                              uint32_t evid, uint32_t collid, uint32_t vlpi,
+                              struct vcpu **vcpu_ptr)
 {
     paddr_t addr;
     struct vits_itte itte;
@@ -698,6 +698,27 @@ out_unlock:
     return ret;
 }
 
+static int its_handle_discard(struct virt_its *its, uint64_t *cmdptr)
+{
+    uint32_t devid = its_cmd_get_deviceid(cmdptr);
+    uint32_t eventid = its_cmd_get_id(cmdptr);
+    int ret;
+
+    spin_lock(&its->its_lock);
+
+    /* Remove from the radix tree and remove the host entry. */
+    ret = its_discard_event(its, devid, eventid);
+
+    /* Remove from the guest's ITTE. */
+    if ( ret || write_itte_locked(its, devid, eventid,
+                                  UNMAPPED_COLLECTION, INVALID_LPI, NULL) )
+        ret = -1;
+
+    spin_unlock(&its->its_lock);
+
+    return ret;
+}
+
 #define ITS_CMD_BUFFER_SIZE(baser)      ((((baser) & 0xff) + 1) << 12)
 #define ITS_CMD_OFFSET(reg)             ((reg) & GENMASK(19, 5))
 
@@ -730,6 +751,9 @@ static int vgic_its_handle_cmds(struct domain *d, struct 
virt_its *its)
         case GITS_CMD_CLEAR:
             ret = its_handle_clear(its, command);
             break;
+        case GITS_CMD_DISCARD:
+            ret = its_handle_discard(its, command);
+            break;
         case GITS_CMD_INT:
             ret = its_handle_int(its, command);
             break;
-- 
2.8.2


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