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Re: [Xen-devel] [PATCH v9 23/28] ARM: vITS: handle DISCARD command



Hi Andre,

On 11/05/17 18:53, Andre Przywara wrote:
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 | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
index ef7c78f..f7a8d77 100644
--- a/xen/arch/arm/vgic-v3-its.c
+++ b/xen/arch/arm/vgic-v3-its.c
@@ -723,6 +723,27 @@ 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) )

I am not sure to fully understand this if. If ret is not NULL you override it and never call write_itte_locked.

Is it what you wanted? If so, then probably a bit more documentation would be useful to explain why writte_itte_locked is skipped.

+        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))

@@ -755,6 +776,9 @@ 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;


Cheers,

--
Julien Grall

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