arm: Move system PPB container handling to armv7m

Instead of having the NVIC device provide a single sysbus memory
region covering the whole of the "System PPB" space, which implements
the default behaviour for unimplemented ranges and provides the NS
alias window to the sysregs as well as the main sysreg MR, move this
handling to the container armv7m device.  The NVIC now provides a
single memory region which just implements the system registers.
This consolidates all the handling of "map various devices in the
PPB" into the armv7m container where it belongs.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alexandre Iooss <erdnaxe@crans.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Message-id: 20210812093356.1946-4-peter.maydell@linaro.org

1 files changed, 99 insertions, 1 deletions

diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
index 364ac06..899159f 100644
--- a/hw/arm/armv7m.c
+++ b/hw/arm/armv7m.c
@@ -18,6 +18,7 @@
 #include "sysemu/reset.h"
 #include "qemu/error-report.h"
 #include "qemu/module.h"
+#include "qemu/log.h"
 #include "target/arm/idau.h"
 
 /* Bitbanded IO.  Each word corresponds to a single bit.  */
@@ -203,6 +204,43 @@ static const MemoryRegionOps v7m_systick_ops = {
     .endianness = DEVICE_NATIVE_ENDIAN,
 };
 
+/*
+ * Unassigned portions of the PPB space are RAZ/WI for privileged
+ * accesses, and fault for non-privileged accesses.
+ */
+static MemTxResult ppb_default_read(void *opaque, hwaddr addr,
+                                    uint64_t *data, unsigned size,
+                                    MemTxAttrs attrs)
+{
+    qemu_log_mask(LOG_UNIMP, "Read of unassigned area of PPB: offset 0x%x\n",
+                  (uint32_t)addr);
+    if (attrs.user) {
+        return MEMTX_ERROR;
+    }
+    *data = 0;
+    return MEMTX_OK;
+}
+
+static MemTxResult ppb_default_write(void *opaque, hwaddr addr,
+                                     uint64_t value, unsigned size,
+                                     MemTxAttrs attrs)
+{
+    qemu_log_mask(LOG_UNIMP, "Write of unassigned area of PPB: offset 0x%x\n",
+                  (uint32_t)addr);
+    if (attrs.user) {
+        return MEMTX_ERROR;
+    }
+    return MEMTX_OK;
+}
+
+static const MemoryRegionOps ppb_default_ops = {
+    .read_with_attrs = ppb_default_read,
+    .write_with_attrs = ppb_default_write,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+    .valid.min_access_size = 1,
+    .valid.max_access_size = 8,
+};
+
 static void armv7m_instance_init(Object *obj)
 {
     ARMv7MState *s = ARMV7M(obj);
@@ -309,13 +347,73 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
     qdev_pass_gpios(DEVICE(&s->nvic), dev, "SYSRESETREQ");
     qdev_pass_gpios(DEVICE(&s->nvic), dev, "NMI");
 
+    /*
+     * We map various devices into the container MR at their architected
+     * addresses. In particular, we map everything corresponding to the
+     * "System PPB" space. This is the range from 0xe0000000 to 0xe00fffff
+     * and includes the NVIC, the System Control Space (system registers),
+     * the systick timer, and for CPUs with the Security extension an NS
+     * banked version of all of these.
+     *
+     * The default behaviour for unimplemented registers/ranges
+     * (for instance the Data Watchpoint and Trace unit at 0xe0001000)
+     * is to RAZ/WI for privileged access and BusFault for non-privileged
+     * access.
+     *
+     * The NVIC and System Control Space (SCS) starts at 0xe000e000
+     * and looks like this:
+     *  0x004 - ICTR
+     *  0x010 - 0xff - systick
+     *  0x100..0x7ec - NVIC
+     *  0x7f0..0xcff - Reserved
+     *  0xd00..0xd3c - SCS registers
+     *  0xd40..0xeff - Reserved or Not implemented
+     *  0xf00 - STIR
+     *
+     * Some registers within this space are banked between security states.
+     * In v8M there is a second range 0xe002e000..0xe002efff which is the
+     * NonSecure alias SCS; secure accesses to this behave like NS accesses
+     * to the main SCS range, and non-secure accesses (including when
+     * the security extension is not implemented) are RAZ/WI.
+     * Note that both the main SCS range and the alias range are defined
+     * to be exempt from memory attribution (R_BLJT) and so the memory
+     * transaction attribute always matches the current CPU security
+     * state (attrs.secure == env->v7m.secure). In the v7m_sysreg_ns_ops
+     * wrappers we change attrs.secure to indicate the NS access; so
+     * generally code determining which banked register to use should
+     * use attrs.secure; code determining actual behaviour of the system
+     * should use env->v7m.secure.
+     *
+     * Within the PPB space, some MRs overlap, and the priority
+     * of overlapping regions is:
+     *  - default region (for RAZ/WI and BusFault) : -1
+     *  - system register regions (provided by the NVIC) : 0
+     *  - systick : 1
+     * This is because the systick device is a small block of registers
+     * in the middle of the other system control registers.
+     */
+
+    memory_region_init_io(&s->defaultmem, OBJECT(s), &ppb_default_ops, s,
+                          "nvic-default", 0x100000);
+    memory_region_add_subregion_overlap(&s->container, 0xe0000000,
+                                        &s->defaultmem, -1);
+
     /* Wire the NVIC up to the CPU */
     sbd = SYS_BUS_DEVICE(&s->nvic);
     sysbus_connect_irq(sbd, 0,
                        qdev_get_gpio_in(DEVICE(s->cpu), ARM_CPU_IRQ));
 
-    memory_region_add_subregion(&s->container, 0xe0000000,
+    memory_region_add_subregion(&s->container, 0xe000e000,
                                 sysbus_mmio_get_region(sbd, 0));
+    if (arm_feature(&s->cpu->env, ARM_FEATURE_V8)) {
+        /* Create the NS alias region for the NVIC sysregs */
+        memory_region_init_io(&s->sysreg_ns_mem, OBJECT(s),
+                              &v7m_sysreg_ns_ops,
+                              sysbus_mmio_get_region(sbd, 0),
+                              "nvic_sysregs_ns", 0x1000);
+        memory_region_add_subregion(&s->container, 0xe002e000,
+                                    &s->sysreg_ns_mem);
+    }
 
     /* Create and map the systick devices */
     if (!sysbus_realize(SYS_BUS_DEVICE(&s->systick[M_REG_NS]), errp)) {