[Xen-devel] [PATCH 2/3] xen/arm: domain_build: Rework the way to allocate the event channel interrupt

[julien.grall@xxxxxxx]

From: Julien Grall <julien.grall@xxxxxxx>

At the moment, a placeholder will be created in the device-tree for the
event channel information. Later in the domain construction, the
interrupt for the event channel upcall will be allocated the device-tree
fixed up.

Looking at the code, the current split is not necessary because all the
PPIs used by the hardware domain will by the time we create the node in
the device-tree.

From now, mandate that all interrupts are registered before
acpi_prepare() and dtb_prepare(). This allows us to rework the event
channel code and remove one placeholder.

Note, this will also help to fix the BUG(...) condition in set_interrupt_ppi
which is completely wrong. See in a follow-up patch.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
 xen/arch/arm/domain_build.c | 74 +++++++++++++++++++++------------------------
 1 file changed, 35 insertions(+), 39 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index a5e5c82355..ed1a393bb5 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -576,7 +576,10 @@ static int make_memory_node(const struct domain *d,
     return res;
 }
 
-static int make_hypervisor_node(const struct kernel_info *kinfo,
+static void evtchn_allocate(struct domain *d);
+
+static int make_hypervisor_node(struct domain *d,
+                                const struct kernel_info *kinfo,
                                 const struct dt_device_node *parent)
 {
     const char compat[] =
@@ -620,10 +623,18 @@ static int make_hypervisor_node(const struct kernel_info 
*kinfo,
         return res;
 
     /*
-     * Placeholder for the event channel interrupt.  The values will be
-     * replaced later.
+     * It is safe to allocate the event channel here because all the
+     * PPIs used by the hardware domain have been registered.
+     */
+    evtchn_allocate(d);
+
+    /*
+     * Interrupt event channel upcall:
+     *  - Active-low level-sensitive
+     *  - All CPUs
+     *  TODO: Handle properly the cpumask;
      */
-    set_interrupt_ppi(intr, ~0, 0xf, IRQ_TYPE_INVALID);
+    set_interrupt_ppi(intr, d->arch.evtchn_irq, 0xf, IRQ_TYPE_LEVEL_LOW);
     res = fdt_property_interrupts(fdt, &intr, 1);
     if ( res )
         return res;
@@ -1282,7 +1293,11 @@ static int handle_node(struct domain *d, struct 
kernel_info *kinfo,
 
     if ( node == dt_host )
     {
-        res = make_hypervisor_node(kinfo, node);
+        /*
+         * The hypervisor node should always be created after all nodes
+         * from the host DT have been parsed.
+         */
+        res = make_hypervisor_node(d, kinfo, node);
         if ( res )
             return res;
 
@@ -1939,6 +1954,12 @@ static int prepare_acpi(struct domain *d, struct 
kernel_info *kinfo)
     if ( rc != 0 )
         return rc;
 
+    /*
+     * All PPIs have been registered, allocate the event channel
+     * interrupts.
+     */
+    evtchn_allocate(d);
+
     return 0;
 }
 #else
@@ -2014,16 +2035,18 @@ static void initrd_load(struct kernel_info *kinfo)
         panic("Unable to copy the initrd in the hwdom memory");
 }
 
-static void evtchn_fixup(struct domain *d, struct kernel_info *kinfo)
+/*
+ * Allocate the event channel PPIs and setup the HVM_PARAM_CALLBACK_IRQ.
+ * The allocated IRQ will be found in d->arch.evtchn_irq.
+ *
+ * Note that this should only be called once all PPIs used by the
+ * hardware domain have been registered.
+ */
+static void evtchn_allocate(struct domain *d)
 {
-    int res, node;
+    int res;
     u64 val;
-    gic_interrupt_t intr;
 
-    /*
-     * The allocation of the event channel IRQ has been deferred until
-     * now. At this time, all PPIs used by DOM0 have been registered.
-     */
     res = vgic_allocate_ppi(d);
     if ( res < 0 )
         panic("Unable to allocate a PPI for the event channel interrupt\n");
@@ -2041,31 +2064,6 @@ static void evtchn_fixup(struct domain *d, struct 
kernel_info *kinfo)
                      HVM_PARAM_CALLBACK_TYPE_PPI_FLAG_MASK);
     val |= d->arch.evtchn_irq;
     d->arch.hvm_domain.params[HVM_PARAM_CALLBACK_IRQ] = val;
-
-    /*
-     * When booting Dom0 using ACPI, Dom0 can only get the event channel
-     * interrupt via hypercall.
-     */
-    if ( !acpi_disabled )
-        return;
-
-    /* Fix up "interrupts" in /hypervisor node */
-    node = fdt_path_offset(kinfo->fdt, "/hypervisor");
-    if ( node < 0 )
-        panic("Cannot find the /hypervisor node");
-
-    /* Interrupt event channel upcall:
-     *  - Active-low level-sensitive
-     *  - All CPUs
-     *
-     *  TODO: Handle properly the cpumask
-     */
-    set_interrupt_ppi(intr, d->arch.evtchn_irq, 0xf,
-                      IRQ_TYPE_LEVEL_LOW);
-    res = fdt_setprop_inplace(kinfo->fdt, node, "interrupts",
-                              &intr, sizeof(intr));
-    if ( res )
-        panic("Cannot fix up \"interrupts\" property of the hypervisor node");
 }
 
 static void __init find_gnttab_region(struct domain *d,
@@ -2177,8 +2175,6 @@ int construct_dom0(struct domain *d)
     kernel_load(&kinfo);
     /* initrd_load will fix up the fdt, so call it before dtb_load */
     initrd_load(&kinfo);
-    /* Allocate the event channel IRQ and fix up the device tree */
-    evtchn_fixup(d, &kinfo);
     dtb_load(&kinfo);
 
     /* Now that we are done restore the original p2m and current. */
-- 
2.11.0


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