When I reviewed Marc's fw_cfg DMA patches, I completely missed that the
way we set dma_enabled would break migration.
Gerd explained the right way (see reference below): dma_enabled should be
set to true by default, and only true->false transitions should be
possible:
- when the user requests that with
-global fw_cfg_mem.dma_enabled=off
or
-global fw_cfg_io.dma_enabled=off
as appropriate for the platform,
- when HW_COMPAT_2_4 dictates it,
- when board code initializes fw_cfg without requesting DMA support.
Cc: Marc Marí <mar...@redhat.com>
Cc: Gerd Hoffmann <kra...@redhat.com>
Cc: Alexandre DERUMIER <aderum...@odiso.com>
Cc: qemu-sta...@nongnu.org
Ref: http://thread.gmane.org/gmane.comp.emulators.qemu/390272/focus=391042
Ref: https://bugs.launchpad.net/qemu/+bug/1536487
Suggested-by: Gerd Hoffmann <kra...@redhat.com>
Signed-off-by: Laszlo Ersek <ler...@redhat.com>
---
Notes:
Tested the following cases with gdb, using qemu-system-x86_64, setting a
breakpoint on (s->dma_enabled) in fw_cfg_init_io_dma():
* no special params (DMA enabled)
* -global fw_cfg_io.dma_enabled=off (DMA disabled)
* -M pc-i440fx-2.4 (DMA disabled), similarly with 2.3 and Q35 too
Also tested the memory mapped case in practice, using
qemu-system-aarch64 -M virt, -kernel / -initrd / -append, with guest
UEFI:
* no special params (DMA enabled)
* -global fw_cfg_mem.dma_enabled=off (DMA disabled)
Not tested:
* actual migration
* when board code doesn't request DMA support
Testing feedback from people who use migration would be nice.
include/hw/compat.h | 8 ++++++++
hw/nvram/fw_cfg.c | 20 ++++++++++++--------
2 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/include/hw/compat.h b/include/hw/compat.h
index 2ebe739fcb5c..a5dbbf8984b1 100644
--- a/include/hw/compat.h
+++ b/include/hw/compat.h
@@ -42,6 +42,14 @@
.driver = "virtio-pci",\
.property = "migrate-extra",\
.value = "off",\
+ },{\
+ .driver = "fw_cfg_mem",\
+ .property = "dma_enabled",\
+ .value = "off",\
+ },{\
+ .driver = "fw_cfg_io",\
+ .property = "dma_enabled",\
+ .value = "off",\
},
#define HW_COMPAT_2_3 \
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 79c5742b3362..f3acb47bd4dc 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -778,17 +778,19 @@ FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t
dma_iobase,
DeviceState *dev;
FWCfgState *s;
uint32_t version = FW_CFG_VERSION;
- bool dma_enabled = dma_iobase && dma_as;
+ bool dma_requested = dma_iobase && dma_as;
dev = qdev_create(NULL, TYPE_FW_CFG_IO);
qdev_prop_set_uint32(dev, "iobase", iobase);
qdev_prop_set_uint32(dev, "dma_iobase", dma_iobase);
- qdev_prop_set_bit(dev, "dma_enabled", dma_enabled);
+ if (!dma_requested) {
+ qdev_prop_set_bit(dev, "dma_enabled", false);
+ }
fw_cfg_init1(dev);
s = FW_CFG(dev);
- if (dma_enabled) {
+ if (s->dma_enabled) {
/* 64 bits for the address field */
s->dma_as = dma_as;
s->dma_addr = 0;
@@ -814,11 +816,13 @@ FWCfgState *fw_cfg_init_mem_wide(hwaddr ctl_addr,
SysBusDevice *sbd;
FWCfgState *s;
uint32_t version = FW_CFG_VERSION;
- bool dma_enabled = dma_addr && dma_as;
+ bool dma_requested = dma_addr && dma_as;
dev = qdev_create(NULL, TYPE_FW_CFG_MEM);
qdev_prop_set_uint32(dev, "data_width", data_width);
- qdev_prop_set_bit(dev, "dma_enabled", dma_enabled);
+ if (!dma_requested) {
+ qdev_prop_set_bit(dev, "dma_enabled", false);
+ }
fw_cfg_init1(dev);
@@ -828,7 +832,7 @@ FWCfgState *fw_cfg_init_mem_wide(hwaddr ctl_addr,
s = FW_CFG(dev);
- if (dma_enabled) {
+ if (s->dma_enabled) {
s->dma_as = dma_as;
s->dma_addr = 0;
sysbus_mmio_map(sbd, 2, dma_addr);
@@ -873,7 +877,7 @@ static Property fw_cfg_io_properties[] = {
DEFINE_PROP_UINT32("iobase", FWCfgIoState, iobase, -1),
DEFINE_PROP_UINT32("dma_iobase", FWCfgIoState, dma_iobase, -1),
DEFINE_PROP_BOOL("dma_enabled", FWCfgIoState, parent_obj.dma_enabled,
- false),
+ true),
DEFINE_PROP_END_OF_LIST(),
};
@@ -913,7 +917,7 @@ static const TypeInfo fw_cfg_io_info = {
static Property fw_cfg_mem_properties[] = {
DEFINE_PROP_UINT32("data_width", FWCfgMemState, data_width, -1),
DEFINE_PROP_BOOL("dma_enabled", FWCfgMemState, parent_obj.dma_enabled,
- false),
+ true),
DEFINE_PROP_END_OF_LIST(),
};
--
1.8.3.1
