[PATCH v3 13/16] KVM: arm64: sync LPI configuration and pending tables

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

The LPI configuration and pending tables of the GICv3 LPIs are held
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 configuration and pending tables in the kernel.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
Changelog v2..v3:
- rework functions to avoid propbaser/pendbaser accesses inside lock

 include/kvm/arm_vgic.h  |   2 +
 virt/kvm/arm/its-emul.c | 133 ++++++++++++++++++++++++++++++++++++++++++++++++
 virt/kvm/arm/its-emul.h |   3 ++
 3 files changed, 138 insertions(+)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 035911f..4ea023c 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -179,6 +179,8 @@ struct vgic_its {
 	int			cwriter;
 	struct list_head	device_list;
 	struct list_head	collection_list;
+	/* memory used for buffering guest's memory */
+	void			*buffer_page;
 };
 
 struct vgic_dist {
diff --git a/virt/kvm/arm/its-emul.c b/virt/kvm/arm/its-emul.c
index 8349970..7a8c5db 100644
--- a/virt/kvm/arm/its-emul.c
+++ b/virt/kvm/arm/its-emul.c
@@ -59,6 +59,7 @@ struct its_itte {
 	struct its_collection *collection;
 	u32 lpi;
 	u32 event_id;
+	u8 priority;
 	bool enabled;
 	unsigned long *pending;
 };
@@ -80,8 +81,124 @@ 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_config(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)
 
+static int nr_idbits_propbase(u64 propbaser)
+{
+	int nr_idbits = (1U << (propbaser & 0x1f)) + 1;
+
+	return max(nr_idbits, INTERRUPT_ID_BITS_ITS);
+}
+
+/*
+ * Scan the whole LPI configuration table and put the LPI configuration
+ * data in our own data structures. This relies on the LPI being
+ * mapped before.
+ */
+static bool its_update_lpis_configuration(struct kvm *kvm, u64 prop_base_reg)
+{
+	struct vgic_dist *dist = &kvm->arch.vgic;
+	u8 *prop = dist->its.buffer_page;
+	u32 tsize;
+	gpa_t propbase;
+	int lpi = GIC_LPI_OFFSET;
+	struct its_itte *itte;
+	struct its_device *device;
+	int ret;
+
+	propbase = BASER_BASE_ADDRESS(prop_base_reg);
+	tsize = nr_idbits_propbase(prop_base_reg);
+
+	while (tsize > 0) {
+		int chunksize = min(tsize, CHUNK_SIZE);
+
+		ret = kvm_read_guest(kvm, propbase, prop, chunksize);
+		if (ret)
+			return false;
+
+		spin_lock(&dist->its.lock);
+		/*
+		 * 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) {
+			if (itte->lpi < lpi || itte->lpi >= lpi + chunksize)
+				continue;
+
+			update_lpi_config(kvm, itte, prop[itte->lpi - lpi]);
+		}
+		spin_unlock(&dist->its.lock);
+		tsize -= chunksize;
+		lpi += chunksize;
+		propbase += chunksize;
+	}
+
+	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.
+ */
+static bool its_sync_lpi_pending_table(struct kvm_vcpu *vcpu, u64 base_addr_reg)
+{
+	struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
+	unsigned long *pendmask = dist->its.buffer_page;
+	u32 nr_lpis = VITS_NR_LPIS;
+	gpa_t pendbase;
+	int lpi = 0;
+	struct its_itte *itte;
+	struct its_device *device;
+	int ret;
+	int lpi_bit, nr_bits;
+
+	pendbase = BASER_BASE_ADDRESS(base_addr_reg);
+
+	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)
+			return false;
+
+		spin_lock(&dist->its.lock);
+		for_each_lpi(device, itte, vcpu->kvm) {
+			lpi_bit = itte->lpi - lpi;
+			if (lpi_bit < 0 || 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);
+		}
+		spin_unlock(&dist->its.lock);
+		nr_lpis -= nr_bits;
+		lpi += nr_bits;
+		pendbase += nr_bits / 8;
+	}
+
+	return true;
+}
+
 /* The distributor lock is held by the VGIC MMIO handler. */
 static bool handle_mmio_misc_gits(struct kvm_vcpu *vcpu,
 				  struct kvm_exit_mmio *mmio,
@@ -418,6 +535,17 @@ static const struct vgic_io_range vgicv3_its_ranges[] = {
 /* This is called on setting the LPI enable bit in the redistributor. */
 void vgic_enable_lpis(struct kvm_vcpu *vcpu)
 {
+	struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
+	u64 prop_base_reg, pend_base_reg;
+
+	pend_base_reg = dist->pendbaser[vcpu->vcpu_id];
+	prop_base_reg = dist->propbaser;
+	spin_unlock(&dist->lock);
+
+	its_update_lpis_configuration(vcpu->kvm, prop_base_reg);
+	its_sync_lpi_pending_table(vcpu, pend_base_reg);
+
+	spin_lock(&dist->lock);
 }
 
 int vits_init(struct kvm *kvm)
@@ -429,6 +557,10 @@ int vits_init(struct kvm *kvm)
 	if (!dist->pendbaser)
 		return -ENOMEM;
 
+	its->buffer_page = kmalloc(CHUNK_SIZE, GFP_KERNEL);
+	if (!its->buffer_page)
+		return -ENOMEM;
+
 	spin_lock_init(&its->lock);
 
 	INIT_LIST_HEAD(&its->device_list);
@@ -474,6 +606,7 @@ void vits_destroy(struct kvm *kvm)
 		kfree(container_of(cur, struct its_collection, coll_list));
 	}
 
+	kfree(its->buffer_page);
 	kfree(dist->pendbaser);
 
 	its->enabled = false;
diff --git a/virt/kvm/arm/its-emul.h b/virt/kvm/arm/its-emul.h
index cc5d5ff..cbc3877 100644
--- a/virt/kvm/arm/its-emul.h
+++ b/virt/kvm/arm/its-emul.h
@@ -29,6 +29,9 @@
 
 #include "vgic.h"
 
+#define INTERRUPT_ID_BITS_ITS 16
+#define VITS_NR_LPIS (1U << INTERRUPT_ID_BITS_ITS)
+
 void vgic_enable_lpis(struct kvm_vcpu *vcpu);
 int vits_init(struct kvm *kvm);
 void vits_destroy(struct kvm *kvm);
-- 
2.5.1