[Qemu-devel] [PATCH v2 3/6] hw/intc/arm_gic_common: Configure IRQs as NS if doing direct NS kernel boot

[Peter Maydell <peter.maydell@linaro.org>]

If we directly boot a kernel in NonSecure on a system where the GIC
supports the security extensions then we must cause the GIC to
configure its interrupts into group 1 (NonSecure) rather than the
usual group 0, and with their initial priority set to the highest
NonSecure priority rather than the usual highest Secure priority.
Otherwise the guest kernel will be unable to use any interrupts.

Implement this behaviour, controlled by a flag which we set if
appropriate when the ARM bootloader code calls our ARMLinuxBootIf
interface callback.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/intc/arm_gic_common.c         | 51 +++++++++++++++++++++++++++++++++++++---
 include/hw/intc/arm_gic_common.h |  1 +
 2 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/hw/intc/arm_gic_common.c b/hw/intc/arm_gic_common.c
index a64d071..ae7c74e 100644
--- a/hw/intc/arm_gic_common.c
+++ b/hw/intc/arm_gic_common.c
@@ -19,6 +19,7 @@
  */
 
 #include "gic_internal.h"
+#include "hw/arm/linux-boot-if.h"
 
 static void gic_pre_save(void *opaque)
 {
@@ -124,12 +125,27 @@ static void arm_gic_common_reset(DeviceState *dev)
 {
     GICState *s = ARM_GIC_COMMON(dev);
     int i, j;
+    int resetprio;
+
+    /* If we're resetting a TZ-aware GIC as if secure firmware
+     * had set it up ready to start a kernel in non-secure,
+     * we need to set interrupt priorities to a "zero for the
+     * NS view" value. This is particularly critical for the
+     * priority_mask[] values, because if they are zero then NS
+     * code cannot ever rewrite the priority to anything else.
+     */
+    if (s->security_extn && s->irq_reset_nonsecure) {
+        resetprio = 0x80;
+    } else {
+        resetprio = 0;
+    }
+
     memset(s->irq_state, 0, GIC_MAXIRQ * sizeof(gic_irq_state));
     for (i = 0 ; i < s->num_cpu; i++) {
         if (s->revision == REV_11MPCORE) {
             s->priority_mask[i] = 0xf0;
         } else {
-            s->priority_mask[i] = 0;
+            s->priority_mask[i] = resetprio;
         }
         s->current_pending[i] = 1023;
         s->running_irq[i] = 1023;
@@ -138,7 +154,7 @@ static void arm_gic_common_reset(DeviceState *dev)
         s->bpr[i] = GIC_MIN_BPR;
         s->abpr[i] = GIC_MIN_ABPR;
         for (j = 0; j < GIC_INTERNAL; j++) {
-            s->priority1[j][i] = 0;
+            s->priority1[j][i] = resetprio;
         }
         for (j = 0; j < GIC_NR_SGIS; j++) {
             s->sgi_pending[j][i] = 0;
@@ -150,7 +166,7 @@ static void arm_gic_common_reset(DeviceState *dev)
     }
 
     for (i = 0; i < ARRAY_SIZE(s->priority2); i++) {
-        s->priority2[i] = 0;
+        s->priority2[i] = resetprio;
     }
 
     for (i = 0; i < GIC_MAXIRQ; i++) {
@@ -161,9 +177,32 @@ static void arm_gic_common_reset(DeviceState *dev)
             s->irq_target[i] = 0;
         }
     }
+    if (s->security_extn && s->irq_reset_nonsecure) {
+        for (i = 0; i < GIC_MAXIRQ; i++) {
+            GIC_SET_GROUP(i, ALL_CPU_MASK);
+        }
+    }
+
     s->ctlr = 0;
 }
 
+static void arm_gic_common_linux_init(ARMLinuxBootIf *obj,
+                                      bool secure_boot)
+{
+    GICState *s = ARM_GIC_COMMON(obj);
+
+    if (s->security_extn && !secure_boot) {
+        /* We're directly booting a kernel into NonSecure. If this GIC
+         * implements the security extensions then we must configure it
+         * to have all the interrupts be NonSecure (this is a job that
+         * is done by the Secure boot firmware in real hardware, and in
+         * this mode QEMU is acting as a minimalist firmware-and-bootloader
+         * equivalent).
+         */
+        s->irq_reset_nonsecure = true;
+    }
+}
+
 static Property arm_gic_common_properties[] = {
     DEFINE_PROP_UINT32("num-cpu", GICState, num_cpu, 1),
     DEFINE_PROP_UINT32("num-irq", GICState, num_irq, 32),
@@ -180,11 +219,13 @@ static Property arm_gic_common_properties[] = {
 static void arm_gic_common_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
+    ARMLinuxBootIfClass *albifc = ARM_LINUX_BOOT_IF_CLASS(klass);
 
     dc->reset = arm_gic_common_reset;
     dc->realize = arm_gic_common_realize;
     dc->props = arm_gic_common_properties;
     dc->vmsd = &vmstate_gic;
+    albifc->arm_linux_init = arm_gic_common_linux_init;
 }
 
 static const TypeInfo arm_gic_common_type = {
@@ -194,6 +235,10 @@ static const TypeInfo arm_gic_common_type = {
     .class_size = sizeof(ARMGICCommonClass),
     .class_init = arm_gic_common_class_init,
     .abstract = true,
+    .interfaces = (InterfaceInfo []) {
+        { TYPE_ARM_LINUX_BOOT_IF },
+        { },
+    },
 };
 
 static void register_types(void)
diff --git a/include/hw/intc/arm_gic_common.h b/include/hw/intc/arm_gic_common.h
index 899db3d..cfc1cce 100644
--- a/include/hw/intc/arm_gic_common.h
+++ b/include/hw/intc/arm_gic_common.h
@@ -118,6 +118,7 @@ typedef struct GICState {
     uint32_t num_irq;
     uint32_t revision;
     bool security_extn;
+    bool irq_reset_nonsecure; /* configure IRQs as group 1 (NS) on reset? */
     int dev_fd; /* kvm device fd if backed by kvm vgic support */
 } GICState;
 
-- 
1.9.1