[PATCH] mac_nvram: Add block backend to persist NVRAM contents

[BALATON Zoltan]

Add a way to set a backing store for the mac_nvram similar to what
spapr_nvram or mac_via PRAM already does to allow to save its contents
between runs. Use -drive file=nvram.img,format=raw,if=mtd to specify
backing file where nvram.img must be MACIO_NVRAM_SIZE which is 8192
bytes. It is only wired for mac_oldworld for now but could be used by
mac_newworld in the future too.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/nvram/mac_nvram.c         | 28 ++++++++++++++++++++++++++++
 hw/ppc/mac_oldworld.c        |  8 +++++++-
 include/hw/nvram/mac_nvram.h |  1 +
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/hw/nvram/mac_nvram.c b/hw/nvram/mac_nvram.c
index 3d9ddda217..810e84f07e 100644
--- a/hw/nvram/mac_nvram.c
+++ b/hw/nvram/mac_nvram.c
@@ -24,9 +24,12 @@
  */
 
 #include "qemu/osdep.h"
+#include "qapi/error.h"
 #include "hw/nvram/chrp_nvram.h"
 #include "hw/nvram/mac_nvram.h"
 #include "hw/qdev-properties.h"
+#include "hw/qdev-properties-system.h"
+#include "sysemu/block-backend.h"
 #include "migration/vmstate.h"
 #include "qemu/cutils.h"
 #include "qemu/module.h"
@@ -44,6 +47,9 @@ static void macio_nvram_writeb(void *opaque, hwaddr addr,
     addr = (addr >> s->it_shift) & (s->size - 1);
     trace_macio_nvram_write(addr, value);
     s->data[addr] = value;
+    if (s->blk) {
+        blk_pwrite(s->blk, addr, 1, &s->data[addr], 0);
+    }
 }
 
 static uint64_t macio_nvram_readb(void *opaque, hwaddr addr,
@@ -91,6 +97,27 @@ static void macio_nvram_realizefn(DeviceState *dev, Error 
**errp)
 
     s->data = g_malloc0(s->size);
 
+    if (s->blk) {
+        int64_t len = blk_getlength(s->blk);
+        if (len < 0) {
+            error_setg_errno(errp, -len,
+                             "could not get length of nvram backing image");
+            return;
+        } else if (len != s->size) {
+            error_setg_errno(errp, -len,
+                             "invalid size nvram backing image");
+            return;
+        }
+        if (blk_set_perm(s->blk, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE,
+                         BLK_PERM_ALL, errp) < 0) {
+            return;
+        }
+        if (blk_pread(s->blk, 0, s->size, s->data, 0) < 0) {
+            error_setg(errp, "can't read-nvram contents");
+            return;
+        }
+    }
+
     memory_region_init_io(&s->mem, OBJECT(s), &macio_nvram_ops, s,
                           "macio-nvram", s->size << s->it_shift);
     sysbus_init_mmio(d, &s->mem);
@@ -106,6 +133,7 @@ static void macio_nvram_unrealizefn(DeviceState *dev)
 static Property macio_nvram_properties[] = {
     DEFINE_PROP_UINT32("size", MacIONVRAMState, size, 0),
     DEFINE_PROP_UINT32("it_shift", MacIONVRAMState, it_shift, 0),
+    DEFINE_PROP_DRIVE("drive", MacIONVRAMState, blk),
     DEFINE_PROP_END_OF_LIST()
 };
 
diff --git a/hw/ppc/mac_oldworld.c b/hw/ppc/mac_oldworld.c
index e052ad880e..52e554710f 100644
--- a/hw/ppc/mac_oldworld.c
+++ b/hw/ppc/mac_oldworld.c
@@ -103,7 +103,7 @@ static void ppc_heathrow_init(MachineState *machine)
     DeviceState *dev, *pic_dev, *grackle_dev;
     BusState *adb_bus;
     uint16_t ppc_boot_device;
-    DriveInfo *hd[MAX_IDE_BUS * MAX_IDE_DEVS];
+    DriveInfo *dinfo, *hd[MAX_IDE_BUS * MAX_IDE_DEVS];
     void *fw_cfg;
     uint64_t tbfreq = kvm_enabled() ? kvmppc_get_tbfreq() : TBFREQ;
     uint8_t *spd_data[3] = {};
@@ -256,6 +256,12 @@ static void ppc_heathrow_init(MachineState *machine)
     qdev_prop_set_chr(dev, "chrA", serial_hd(0));
     qdev_prop_set_chr(dev, "chrB", serial_hd(1));
 
+    dinfo = drive_get(IF_MTD, 0, 0);
+    if (dinfo) {
+        dev = DEVICE(object_resolve_path_component(macio, "nvram"));
+        qdev_prop_set_drive(dev, "drive", blk_by_legacy_dinfo(dinfo));
+    }
+
     pci_realize_and_unref(PCI_DEVICE(macio), pci_bus, &error_fatal);
 
     pic_dev = DEVICE(object_resolve_path_component(macio, "pic"));
diff --git a/include/hw/nvram/mac_nvram.h b/include/hw/nvram/mac_nvram.h
index b780aca470..0c4dfaeff6 100644
--- a/include/hw/nvram/mac_nvram.h
+++ b/include/hw/nvram/mac_nvram.h
@@ -44,6 +44,7 @@ struct MacIONVRAMState {
 
     MemoryRegion mem;
     uint8_t *data;
+    BlockBackend *blk;
 };
 
 void pmac_format_nvram_partition(MacIONVRAMState *nvr, int len);
-- 
2.30.6