[Xen-devel] [PATCH v3 09/39] ARM: new VGIC: Add accessor to new struct vgic_irq instance

[Andre Przywara <andre.przywara@xxxxxxxxxx>]

The new VGIC implementation centers around a struct vgic_irq instance
per virtual IRQ.
Provide a function to retrieve the right instance for a given IRQ
number and (in case of private interrupts) the right VCPU.
This also includes the corresponding put function, which does nothing
for private interrupts and SPIs, but handles the ref-counting for LPIs.

This is based on Linux commit 64a959d66e47, written by Christoffer Dall.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
---
Changelog v2 ... v3:
- extend comments to note preliminary nature of vgic_get_lpi()

Changelog v1 ... v2:
- reorder header file inclusion

 xen/arch/arm/vgic/vgic.c | 134 +++++++++++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/vgic/vgic.h |  41 +++++++++++++++
 2 files changed, 175 insertions(+)
 create mode 100644 xen/arch/arm/vgic/vgic.c
 create mode 100644 xen/arch/arm/vgic/vgic.h

diff --git a/xen/arch/arm/vgic/vgic.c b/xen/arch/arm/vgic/vgic.c
new file mode 100644
index 0000000000..a818e382b1
--- /dev/null
+++ b/xen/arch/arm/vgic/vgic.c
@@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2015, 2016 ARM Ltd.
+ * Imported from Linux ("new" KVM VGIC) and heavily adapted to Xen.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <xen/sched.h>
+#include <asm/bug.h>
+#include <asm/new_vgic.h>
+
+#include "vgic.h"
+
+/*
+ * Iterate over the VM's list of mapped LPIs to find the one with a
+ * matching interrupt ID and return a reference to the IRQ structure.
+ *
+ * TODO: This is more documentation of how it should be done. A list is
+ * not a good data structure for Dom0's LPIs, it merely serves as an
+ * example here how to properly do the locking, allocation and refcounting.
+ * So lpi_list_head should be replaced with something more appropriate.
+ */
+static struct vgic_irq *vgic_get_lpi(struct domain *d, u32 intid)
+{
+    struct vgic_dist *dist = &d->arch.vgic;
+    struct vgic_irq *irq = NULL;
+
+    spin_lock(&dist->lpi_list_lock);
+
+    list_for_each_entry( irq, &dist->lpi_list_head, lpi_list )
+    {
+        if ( irq->intid != intid )
+            continue;
+
+        /*
+         * This increases the refcount, the caller is expected to
+         * call vgic_put_irq() later once it's finished with the IRQ.
+         */
+        vgic_get_irq_kref(irq);
+        goto out_unlock;
+    }
+    irq = NULL;
+
+out_unlock:
+    spin_unlock(&dist->lpi_list_lock);
+
+    return irq;
+}
+
+/**
+ * vgic_get_irq() - obtain a reference to a virtual IRQ
+ * @d:        The domain the virtual IRQ belongs to.
+ * @vcpu:     For private IRQs (SGIs, PPIs) the virtual CPU this IRQ
+ *            is associated with. Will be ignored for SPIs and LPIs.
+ * @intid:    The virtual IRQ number.
+ *
+ * This looks up the virtual interrupt ID to get the corresponding
+ * struct vgic_irq. It also increases the refcount, so any caller is expected
+ * to call vgic_put_irq() once it's finished with this IRQ.
+ *
+ * Return: The pointer to the requested struct vgic_irq.
+ */
+struct vgic_irq *vgic_get_irq(struct domain *d, struct vcpu *vcpu,
+                              u32 intid)
+{
+    /* SGIs and PPIs */
+    if ( intid <= VGIC_MAX_PRIVATE )
+        return &vcpu->arch.vgic.private_irqs[intid];
+
+    /* SPIs */
+    if ( intid <= VGIC_MAX_SPI )
+        return &d->arch.vgic.spis[intid - VGIC_NR_PRIVATE_IRQS];
+
+    /* LPIs */
+    if ( intid >= VGIC_MIN_LPI )
+        return vgic_get_lpi(d, intid);
+
+    ASSERT_UNREACHABLE();
+
+    return NULL;
+}
+
+/**
+ * vgic_put_irq() - drop the reference to a virtual IRQ
+ * @d:        The domain the virtual IRQ belongs to.
+ * @irq:      The pointer to struct vgic_irq, as obtained from vgic_get_irq().
+ *
+ * This drops the reference to a virtual IRQ. It decreases the refcount
+ * of the pointer, so dynamic IRQs can be freed when no longer needed.
+ * This should always be called after a vgic_get_irq(), though the reference
+ * can be deliberately held for longer periods, if needed.
+ *
+ * TODO: A linked list is not a good data structure for LPIs in Dom0.
+ * Replace this with proper data structure once we get proper LPI support.
+ */
+void vgic_put_irq(struct domain *d, struct vgic_irq *irq)
+{
+    struct vgic_dist *dist = &d->arch.vgic;
+
+    if ( irq->intid < VGIC_MIN_LPI )
+        return;
+
+    spin_lock(&dist->lpi_list_lock);
+    if ( !atomic_dec_and_test(&irq->refcount) )
+    {
+        spin_unlock(&dist->lpi_list_lock);
+        return;
+    };
+
+    list_del(&irq->lpi_list);
+    dist->lpi_list_count--;
+    spin_unlock(&dist->lpi_list_lock);
+
+    xfree(irq);
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/arm/vgic/vgic.h b/xen/arch/arm/vgic/vgic.h
new file mode 100644
index 0000000000..a3befd386b
--- /dev/null
+++ b/xen/arch/arm/vgic/vgic.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2015, 2016 ARM Ltd.
+ * Imported from Linux ("new" KVM VGIC) and heavily adapted to Xen.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __XEN_ARM_VGIC_VGIC_H__
+#define __XEN_ARM_VGIC_VGIC_H__
+
+struct vgic_irq *vgic_get_irq(struct domain *d, struct vcpu *vcpu,
+                              u32 intid);
+void vgic_put_irq(struct domain *d, struct vgic_irq *irq);
+
+static inline void vgic_get_irq_kref(struct vgic_irq *irq)
+{
+    if ( irq->intid < VGIC_MIN_LPI )
+        return;
+
+    atomic_inc(&irq->refcount);
+}
+
+#endif
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.14.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel