[RFC PATCH 19/24] ARM: vITS: handle DISCARD command

[Andre Przywara <andre.przywara@arm.com>]

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@arm.com>
---
 xen/arch/arm/gic-its.c        | 21 +++++++++++++++++++
 xen/arch/arm/vgic-its.c       | 48 +++++++++++++++++++++++++++++++++++++++++++
 xen/include/asm-arm/gic-its.h |  5 +++++
 3 files changed, 74 insertions(+)

diff --git a/xen/arch/arm/gic-its.c b/xen/arch/arm/gic-its.c
index d1b1cbb..766a7cb 100644
--- a/xen/arch/arm/gic-its.c
+++ b/xen/arch/arm/gic-its.c
@@ -634,6 +634,27 @@ int gicv3_lpi_change_vcpu(struct domain *d, uint32_t host_lpi, int new_vcpu_id)
     return 0;
 }
 
+/* Looks up a given host LPI assigned to that domain and returns the
+ * connected virtual LPI number. Also stores the target vcpu ID in
+ * the passed vcpu_id pointer.
+ * Returns 0 if no host LPI could be found for that domain, or the
+ * virtual LPI number (>= 8192) if the lookup succeeded.
+ */
+uint32_t gicv3_lpi_lookup_lpi(struct domain *d, uint32_t host_lpi, int *vcpu_id)
+{
+    union host_lpi *hlpip, hlpi;
+
+    hlpip = gic_find_host_lpi(host_lpi, d);
+    if ( !hlpip )
+        return 0;
+
+    hlpi.data = hlpip->data;
+    if ( vcpu_id )
+        *vcpu_id = hlpi.vcpu_id;
+
+    return hlpi.virt_lpi;
+}
+
 void gicv3_its_dt_init(const struct dt_device_node *node)
 {
     const struct dt_device_node *its = NULL;
diff --git a/xen/arch/arm/vgic-its.c b/xen/arch/arm/vgic-its.c
index c0a60ad..028d234 100644
--- a/xen/arch/arm/vgic-its.c
+++ b/xen/arch/arm/vgic-its.c
@@ -367,6 +367,51 @@ out_unlock:
     return 0;
 }
 
+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);
+    struct pending_irq *pirq;
+    struct vits_itte *itte;
+    struct vcpu *vcpu;
+    uint32_t vlpi;
+    int ret = -1, vcpu_id;
+
+    spin_lock(&its->its_lock);
+    itte = get_devid_evid(its, devid, eventid);
+    if ( !itte )
+        goto out_unlock;
+
+    vlpi = gicv3_lpi_lookup_lpi(its->d, itte->hlpi, &vcpu_id);
+    if ( !vlpi )
+        goto out_unlock;
+
+    vcpu = its->d->vcpu[vcpu_id];
+
+    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;
+    }
+
+    gicv3_lpi_drop_host_lpi(its->hw_its, devid, eventid, itte->hlpi);
+
+    itte->hlpi = 0;             /* Mark this ITTE as unused. */
+    ret = 0;
+
+    put_devid_evid(its, itte);
+
+out_unlock:
+    spin_unlock(&its->its_lock);
+
+    return ret;
+}
+
 #define ITS_CMD_BUFFER_SIZE(baser)      ((((baser) & 0xff) + 1) << 12)
 
 static int vgic_its_handle_cmds(struct domain *d, struct virt_its *its,
@@ -390,6 +435,9 @@ static int vgic_its_handle_cmds(struct domain *d, struct virt_its *its,
         case GITS_CMD_CLEAR:
             its_handle_clear(its, cmdptr);
             break;
+        case GITS_CMD_DISCARD:
+            its_handle_discard(its, cmdptr);
+            break;
         case GITS_CMD_INT:
             its_handle_int(its, cmdptr);
             break;
diff --git a/xen/include/asm-arm/gic-its.h b/xen/include/asm-arm/gic-its.h
index 7e1142f..3f5698d 100644
--- a/xen/include/asm-arm/gic-its.h
+++ b/xen/include/asm-arm/gic-its.h
@@ -133,6 +133,11 @@ int gicv3_its_map_device(struct host_its *hw_its, struct domain *d,
 int gicv3_lpi_allocate_host_lpi(struct host_its *its,
                                 uint32_t devid, uint32_t eventid,
                                 struct vcpu *v, int virt_lpi);
+/* Given a physical LPI, looks up and returns the associated virtual LPI
+ * and the target VCPU in the given domain.
+ */
+uint32_t gicv3_lpi_lookup_lpi(struct domain *d, uint32_t host_lpi,
+                              int *vcpu_id);
 int gicv3_lpi_change_vcpu(struct domain *d, uint32_t host_lpi, int new_vcpu_id);
 int gicv3_lpi_drop_host_lpi(struct host_its *its,
                             uint32_t devid, uint32_t eventid,
-- 
2.9.0


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