[Xen-devel] [RFC PATCH 13/24] ARM: vITS: handle CLEAR command

[Andre Przywara <andre.przywara@xxxxxxx>]

This introduces the ITS command handler for the CLEAR command, which
clears the pending state of an LPI.
This removes a not-yet injected, but already queued IRQ from a VCPU.

In addition this patch introduces the lookup function which translates
a given DeviceID/EventID pair into a pointer to our vITTE structure.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
 xen/arch/arm/vgic-its.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)

diff --git a/xen/arch/arm/vgic-its.c b/xen/arch/arm/vgic-its.c
index 875b992..99d9e9c 100644
--- a/xen/arch/arm/vgic-its.c
+++ b/xen/arch/arm/vgic-its.c
@@ -61,6 +61,73 @@ struct vits_itte
     uint64_t collection:16;
 };
 
+#define UNMAPPED_COLLECTION      ((uint16_t)~0)
+
+/* Must be called with the ITS lock held. */
+static struct vcpu *get_vcpu_from_collection(struct virt_its *its, int collid)
+{
+    uint16_t vcpu_id;
+
+    if ( collid >= its->max_collections )
+        return NULL;
+
+    vcpu_id = its->coll_table[collid];
+    if ( vcpu_id == UNMAPPED_COLLECTION || vcpu_id >= its->d->max_vcpus )
+        return NULL;
+
+    return its->d->vcpu[vcpu_id];
+}
+
+#define DEV_TABLE_ITT_ADDR(x) ((x) & GENMASK(51, 8))
+#define DEV_TABLE_ITT_SIZE(x) (BIT(((x) & GENMASK(7, 0)) + 1))
+#define DEV_TABLE_ENTRY(addr, bits)                     \
+        (((addr) & GENMASK(51, 8)) | (((bits) - 1) & GENMASK(7, 0)))
+
+static paddr_t get_itte_address(struct virt_its *its,
+                                uint32_t devid, uint32_t evid)
+{
+    paddr_t addr;
+
+    if ( devid >= its->max_devices )
+        return ~0;
+
+    if ( evid >= DEV_TABLE_ITT_SIZE(its->dev_table[devid]) )
+        return ~0;
+
+    addr = DEV_TABLE_ITT_ADDR(its->dev_table[devid]);
+
+    return addr + evid * sizeof(struct vits_itte);
+}
+
+/* Looks up a given deviceID/eventID pair on an ITS and returns a pointer to
+ * the corresponding ITTE. This maps the respective guest page into Xen.
+ * Once finished with handling the ITTE, call put_devid_evid() to unmap
+ * the page again.
+ * Must be called with the ITS lock held.
+ */
+static struct vits_itte *get_devid_evid(struct virt_its *its,
+                                        uint32_t devid, uint32_t evid)
+{
+    paddr_t addr = get_itte_address(its, devid, evid);
+    struct vits_itte *itte;
+
+    if (addr == ~0)
+        return NULL;
+
+    /* TODO: check locking for map_guest_pages() */
+    itte = map_guest_pages(its->d, addr & PAGE_MASK, 1);
+    if ( !itte )
+        return NULL;
+
+    return itte + (addr & ~PAGE_MASK) / sizeof(struct vits_itte);
+}
+
+/* Must be called with the ITS lock held. */
+static void put_devid_evid(struct virt_its *its, struct vits_itte *itte)
+{
+    unmap_guest_pages(itte, 1);
+}
+
 /**************************************
  * Functions that handle ITS commands *
  **************************************/
@@ -80,6 +147,51 @@ static uint64_t its_cmd_mask_field(uint64_t *its_cmd,
 #define its_cmd_get_target_addr(cmd)    its_cmd_mask_field(cmd, 2, 16, 32)
 #define its_cmd_get_validbit(cmd)       its_cmd_mask_field(cmd, 2, 63,  1)
 
+static int its_handle_clear(struct virt_its *its, uint64_t *cmdptr)
+{
+    uint32_t devid = its_cmd_get_deviceid(cmdptr);
+    uint32_t eventid = its_cmd_get_id(cmdptr);
+    struct pending_irq *pirq;
+    struct vits_itte *itte;
+    struct vcpu *vcpu;
+    uint32_t vlpi;
+
+    spin_lock(&its->its_lock);
+
+    itte = get_devid_evid(its, devid, eventid);
+    if ( !itte )
+    {
+        spin_unlock(&its->its_lock);
+        return -1;
+    }
+
+    vcpu = get_vcpu_from_collection(its, itte->collection);
+    if ( !vcpu )
+    {
+        spin_unlock(&its->its_lock);
+        return -1;
+    }
+
+    vlpi = itte->vlpi;
+
+    put_devid_evid(its, itte);
+    spin_unlock(&its->its_lock);
+
+    /* Remove a pending, but not yet injected guest IRQ. */
+    pirq = lpi_to_pending(vcpu, vlpi, false);
+    if ( pirq )
+    {
+        clear_bit(GIC_IRQ_GUEST_QUEUED, &pirq->status);
+        gic_remove_from_queues(vcpu, vlpi);
+
+        /* Mark this pending IRQ struct as availabe again. */
+        if ( !test_bit(GIC_IRQ_GUEST_VISIBLE, &pirq->status) )
+            pirq->irq = 0;
+    }
+
+    return 0;
+}
+
 #define ITS_CMD_BUFFER_SIZE(baser)      ((((baser) & 0xff) + 1) << 12)
 
 static int vgic_its_handle_cmds(struct domain *d, struct virt_its *its,
@@ -100,6 +212,9 @@ static int vgic_its_handle_cmds(struct domain *d, struct 
virt_its *its,
         cmdptr = its->cmdbuf + (its->creadr / sizeof(*its->cmdbuf));
         switch (its_cmd_get_command(cmdptr))
         {
+        case GITS_CMD_CLEAR:
+            its_handle_clear(its, cmdptr);
+            break;
         case GITS_CMD_SYNC:
             /* We handle ITS commands synchronously, so we ignore SYNC. */
            break;
-- 
2.9.0


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