[PATCH 10/13] KVM: arm64: sync LPI properties and status between guest and KVM

[Andre Przywara]

The properties and status of the GICv3 LPIs are hold in tables in
(guest) memory. To achieve reasonable performance, we cache this
data in our own data structures, so we need to sync those two views
from time to time. This behaviour is well described in the GICv3 spec
and is also exercised by hardware, so the sync points are well known.

Provide functions that read the guest memory and store the
information from the property and status table in the kernel.

Signed-off-by: Andre Przywara <andre.przywara at arm.com>
---
 virt/kvm/arm/its-emul.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)

diff --git a/virt/kvm/arm/its-emul.c b/virt/kvm/arm/its-emul.c
index f75fb9e..afd440e 100644
--- a/virt/kvm/arm/its-emul.c
+++ b/virt/kvm/arm/its-emul.c
@@ -50,6 +50,7 @@ struct its_itte {
 	struct its_collection *collection;
 	u32 lpi;
 	u32 event_id;
+	u8 priority;
 	bool enabled;
 	unsigned long *pending;
 };
@@ -70,7 +71,140 @@ static struct its_itte *find_itte_by_lpi(struct kvm *kvm, int lpi)
 	return NULL;
 }
 
+#define LPI_PROP_ENABLE_BIT(p)	((p) & LPI_PROP_ENABLED)
+#define LPI_PROP_PRIORITY(p)	((p) & 0xfc)
+
+/* stores the priority and enable bit for a given LPI */
+static void update_lpi_property(struct kvm *kvm, struct its_itte *itte, u8 prop)
+{
+	itte->priority = LPI_PROP_PRIORITY(prop);
+	itte->enabled  = LPI_PROP_ENABLE_BIT(prop);
+}
+
+#define GIC_LPI_OFFSET 8192
+
+/* We scan the table in chunks the size of the smallest page size */
+#define CHUNK_SIZE 4096U
+
 #define BASER_BASE_ADDRESS(x) ((x) & 0xfffffffff000ULL)
+#define PROPBASE_TSIZE(x) (1U << (x & 0x1f))
+
+/*
+ * Scan the whole LPI property table and put the LPI configuration
+ * data in our own data structures. This relies on the LPI being
+ * mapped before.
+ * We scan from two sides:
+ * 1) for each byte in the table we care for the ones being enabled
+ * 2) for each mapped LPI we look into the table to spot LPIs being disabled
+ * Must be called with the ITS lock held.
+ */
+static bool its_update_lpi_properties(struct kvm *kvm)
+{
+	struct vgic_dist *dist = &kvm->arch.vgic;
+	u8 *prop;
+	u32 tsize;
+	gpa_t propbase;
+	int lpi = GIC_LPI_OFFSET;
+	struct its_itte *itte;
+	struct its_device *device;
+	int ret;
+
+	propbase = BASER_BASE_ADDRESS(dist->propbaser);
+	tsize = PROPBASE_TSIZE(dist->propbaser);
+
+	prop = kmalloc(CHUNK_SIZE, GFP_KERNEL);
+	if (!prop)
+		return false;
+
+	while (tsize > 0) {
+		int chunksize = min(tsize, CHUNK_SIZE);
+
+		ret = kvm_read_guest(kvm, propbase, prop, chunksize);
+		if (ret) {
+			kfree(prop);
+			break;
+		}
+
+		/*
+		 * Updating the status for all allocated LPIs. We catch
+		 * those LPIs that get disabled. We really don't care
+		 * about unmapped LPIs, as they need to be updated
+		 * later manually anyway once they get mapped.
+		 */
+		for_each_lpi(device, itte, kvm) {
+			/*
+			 * Is the LPI covered by that part of the table we
+			 * are currently looking at?
+			 */
+			if (itte->lpi < lpi)
+				continue;
+			if (itte->lpi >= lpi + chunksize)
+				continue;
+
+			update_lpi_property(kvm, itte,
+					    prop[itte->lpi - lpi]);
+		}
+		tsize -= chunksize;
+		lpi += chunksize;
+		propbase += chunksize;
+	}
+
+	kfree(prop);
+	return true;
+}
+
+/*
+ * Scan the whole LPI pending table and sync the pending bit in there
+ * with our own data structures. This relies on the LPI being
+ * mapped before.
+ * Must be called with the ITS lock held.
+ */
+static bool its_sync_lpi_pending_table(struct kvm_vcpu *vcpu)
+{
+	struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
+	unsigned long *pendmask;
+	u32 nr_lpis;
+	gpa_t pendbase;
+	int lpi = GIC_LPI_OFFSET;
+	struct its_itte *itte;
+	struct its_device *device;
+	int ret;
+	int lpi_bit, nr_bits;
+
+	pendbase = BASER_BASE_ADDRESS(dist->pendbaser[vcpu->vcpu_id]);
+	nr_lpis = GIC_LPI_OFFSET;
+
+	pendmask = kmalloc(CHUNK_SIZE, GFP_KERNEL);
+	if (!pendmask)
+		return false;
+
+	while (nr_lpis > 0) {
+		nr_bits = min(nr_lpis, CHUNK_SIZE * 8);
+
+		ret = kvm_read_guest(vcpu->kvm, pendbase, pendmask,
+				     nr_bits / 8);
+		if (ret)
+			break;
+
+		for_each_lpi(device, itte, vcpu->kvm) {
+			lpi_bit = itte->lpi - lpi;
+			if (lpi_bit < 0)
+				continue;
+			if (lpi_bit >= nr_bits)
+				continue;
+			if (test_bit(lpi_bit, pendmask))
+				set_bit(vcpu->vcpu_id, itte->pending);
+			else
+				clear_bit(vcpu->vcpu_id, itte->pending);
+		}
+		nr_lpis -= nr_bits;
+		lpi += nr_bits;
+		pendbase += nr_bits / 8;
+	}
+
+	kfree(pendmask);
+	return true;
+}
 
 /* distributor lock is hold by the VGIC MMIO handler */
 static bool handle_mmio_misc_gits(struct kvm_vcpu *vcpu,
@@ -350,6 +484,12 @@ static const struct vgic_io_range vgicv3_its_ranges[] = {
 
 void vgic_enable_lpis(struct kvm_vcpu *vcpu)
 {
+	struct vgic_its *its = &vcpu->kvm->arch.vgic.its;
+
+	spin_lock(&its->lock);
+	its_update_lpi_properties(vcpu->kvm);
+	its_sync_lpi_pending_table(vcpu);
+	spin_unlock(&its->lock);
 }
 
 int vits_init(struct kvm *kvm)
-- 
2.3.5