From: Andre Przywara <andre.przywara@xxxxxxx>
The LPI pending status for a GICv3 redistributor is held in a table
in (guest) memory. To achieve reasonable performance, we cache the
pending bit in our struct vgic_irq. The initial pending state must be
read from guest memory upon enabling LPIs for this redistributor.
As we can't access the guest memory while we hold the lpi_list spinlock,
we create a snapshot of the LPI list and iterate over that.
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Tested-by: Eric Auger <eric.auger@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
virt/kvm/arm/vgic/vgic-its.c | 95 ++++++++++++++++++++++++++++++++++++++++++++
virt/kvm/arm/vgic/vgic.h | 5 +++
2 files changed, 100 insertions(+)
diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 14f91ff..2881b84 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -67,6 +67,94 @@ struct its_itte {
* supports more. Let's be restrictive here.
*/
#define CBASER_ADDRESS(x) ((x) & GENMASK_ULL(47, 12))
+#define PENDBASER_ADDRESS(x) ((x) & GENMASK_ULL(47, 16))
+
+/*
+ * Create a snapshot of the current LPI list, so that we can enumerate all
+ * LPIs without holding any lock.
+ * Returns the array length and puts the kmalloc'ed array into intid_ptr.
+ */
+static int vgic_copy_lpi_list(struct kvm *kvm, u32 **intid_ptr)
+{
+ struct vgic_dist *dist = &kvm->arch.vgic;
+ struct vgic_irq *irq;
+ u32 *intids;
+ int irq_count = dist->lpi_list_count, i = 0;
+
+ /*
+ * We use the current value of the list length, which may change
+ * after the kmalloc. We don't care, because the guest shouldn't
+ * change anything while the command handling is still running,
+ * and in the worst case we would miss a new IRQ, which one wouldn't
+ * expect to be covered by this command anyway.
+ */
+ intids = kmalloc_array(irq_count, sizeof(intids[0]), GFP_KERNEL);
+ if (!intids)
+ return -ENOMEM;
+
+ spin_lock(&dist->lpi_list_lock);
+ list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) {
+ /* We don't need to "get" the IRQ, as we hold the list lock. */
+ intids[i] = irq->intid;
+ if (++i == irq_count)
+ break;
+ }
+ spin_unlock(&dist->lpi_list_lock);
+
+ *intid_ptr = intids;
+ return irq_count;
+}
+
+/*
+ * 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 int its_sync_lpi_pending_table(struct kvm_vcpu *vcpu)
+{
+ gpa_t pendbase = PENDBASER_ADDRESS(vcpu->arch.vgic_cpu.pendbaser);
+ struct vgic_irq *irq;
+ int last_byte_offset = -1;
+ int ret = 0;
+ u32 *intids;
+ int nr_irqs, i;
+
+ nr_irqs = vgic_copy_lpi_list(vcpu->kvm, &intids);
+ if (nr_irqs < 0)
+ return nr_irqs;
+
+ for (i = 0; i < nr_irqs; i++) {
+ int byte_offset, bit_nr;
+ u8 pendmask;
+
+ byte_offset = intids[i] / BITS_PER_BYTE;
+ bit_nr = intids[i] % BITS_PER_BYTE;
+
+ /*
+ * For contiguously allocated LPIs chances are we just read
+ * this very same byte in the last iteration. Reuse that.
+ */
+ if (byte_offset != last_byte_offset) {
+ ret = kvm_read_guest(vcpu->kvm, pendbase + byte_offset,
+ &pendmask, 1);
+ if (ret) {
+ kfree(intids);
+ return ret;
+ }
+ last_byte_offset = byte_offset;
+ }
+
+ irq = vgic_get_irq(vcpu->kvm, NULL, intids[i]);
+ spin_lock(&irq->irq_lock);
+ irq->pending = pendmask & (1U << bit_nr);
+ vgic_queue_irq_unlock(vcpu->kvm, irq);
+ vgic_put_irq(vcpu->kvm, irq);
+ }
+
+ kfree(intids);
+
+ return ret;
+}
static unsigned long vgic_mmio_read_its_ctlr(struct kvm *vcpu,
struct vgic_its *its,
@@ -403,6 +491,13 @@ static struct vgic_register_region its_registers[] = {
VGIC_ACCESS_32bit),
};
+/* This is called on setting the LPI enable bit in the redistributor. */
+void vgic_enable_lpis(struct kvm_vcpu *vcpu)
+{
+ if (!(vcpu->arch.vgic_cpu.pendbaser & GICR_PENDBASER_PTZ))
+ its_sync_lpi_pending_table(vcpu);
+}
+
static int vgic_its_init_its(struct kvm *kvm, struct vgic_its *its)
{
struct vgic_io_device *iodev = &its->iodev;
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index 8192a29..ee348de 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -25,6 +25,7 @@
#define IS_VGIC_ADDR_UNDEF(_x) ((_x) == VGIC_ADDR_UNDEF)
#define INTERRUPT_ID_BITS_SPIS 10
+#define INTERRUPT_ID_BITS_ITS 16
#define VGIC_PRI_BITS 5
#define vgic_irq_is_sgi(intid) ((intid) < VGIC_NR_SGIS)
@@ -76,6 +77,7 @@ int vgic_v3_probe(const struct gic_kvm_info *info);
int vgic_v3_map_resources(struct kvm *kvm);
int vgic_register_redist_iodevs(struct kvm *kvm, gpa_t dist_base_address);
bool vgic_has_its(struct kvm *kvm);
+void vgic_enable_lpis(struct kvm_vcpu *vcpu);
#else
static inline void vgic_v3_process_maintenance(struct kvm_vcpu *vcpu)
{
@@ -133,6 +135,9 @@ static inline bool vgic_has_its(struct kvm *kvm)
return false;
}
+static inline void vgic_enable_lpis(struct kvm_vcpu *vcpu)
+{
+}
#endif
int kvm_register_vgic_device(unsigned long type);
--
2.8.1
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