| Message ID | 1345893020-4894-1-git-send-email-dzeromsk@gmail.com |
|---|---|
| State | New |
| Headers | show |
On Sat, Aug 25, 2012 at 12:10 PM, Dominik Żeromski <dzeromsk@gmail.com> wrote: > Adding support for loading DSO with -device option. > > Example Makefile for out of tree modules: QEMU does not have a stable ABI for devices. There is a lot of device model refactoring happening right now for multithreaded MMIO/PIO dispatch and taking advantage of QEMU Object Model. A stable ABI hinders those kinds of improvements. Send device model patches upstream. That way you avoid the maintenance overhead of out-of-tree modules and the QEMU community doesn't need to provide a stable ABI. Stefan
2012/8/25 Stefan Hajnoczi <stefanha@gmail.com> > > On Sat, Aug 25, 2012 at 12:10 PM, Dominik Żeromski <dzeromsk@gmail.com> > wrote: > > Adding support for loading DSO with -device option. > > > > Example Makefile for out of tree modules: > > QEMU does not have a stable ABI for devices. There is a lot of device > model refactoring happening right now for multithreaded MMIO/PIO > dispatch and taking advantage of QEMU Object Model. A stable ABI > hinders those kinds of improvements. > > Send device model patches upstream. That way you avoid the > maintenance overhead of out-of-tree modules and the QEMU community > doesn't need to provide a stable ABI. > I think that QEMU is a great tool, not only for server virtualization but also for embedded software and hardware development. I agree that it would be hard to maintain stable ABI, but this is a usability feature for device developers, not QEMU developers. I can imagine use cases where one team works on a hardware emulator and wants to share it with driver team. Driver team doesn't care about how QEMU works, how to configure, compile it and then use it. They probably use qemu-kvm and libvirt provided by some Linux distribution. The distro qemu-kvm does not change much so it wouldn't be a problem for emulator team to fix eventual ABI problems. Distributing device as dynamic library is simply easier for both teams. -Dominik
On Sat, Aug 25, 2012 at 6:06 PM, Dominik Żeromski <dzeromsk@gmail.com> wrote: > 2012/8/25 Stefan Hajnoczi <stefanha@gmail.com> >> >> On Sat, Aug 25, 2012 at 12:10 PM, Dominik Żeromski <dzeromsk@gmail.com> >> wrote: >> > Adding support for loading DSO with -device option. >> > >> > Example Makefile for out of tree modules: >> >> QEMU does not have a stable ABI for devices. There is a lot of device >> model refactoring happening right now for multithreaded MMIO/PIO >> dispatch and taking advantage of QEMU Object Model. A stable ABI >> hinders those kinds of improvements. >> >> Send device model patches upstream. That way you avoid the >> maintenance overhead of out-of-tree modules and the QEMU community >> doesn't need to provide a stable ABI. >> > > I think that QEMU is a great tool, not only for server virtualization > but also for embedded software and hardware development. > > I agree that it would be hard to maintain stable ABI, but this is a > usability feature for device developers, not QEMU developers. I can > imagine use cases where one team works on a hardware emulator and > wants to share it with driver team. Driver team doesn't care about how > QEMU works, how to configure, compile it and then use it. They > probably use qemu-kvm and libvirt provided by some Linux distribution. > The distro qemu-kvm does not change much so it wouldn't be a problem > for emulator team to fix eventual ABI problems. Distributing device as > dynamic library is simply easier for both teams. The hardware team can provide a qemu-custom-board binary instead of a bunch of .so files to the driver team. That way the whole emulator can be tested and will never have ABI issues. Device model plugins don't improve this scenario. Stefan
Dominik Żeromski <dzeromsk@gmail.com> writes: > Adding support for loading DSO with -device option. Hi, A few things: 1) Out of tree modules are boring and there's very little support/sympathy for supporting out of tree modules. That said, if you implemented support for in tree modules and the build system happened to work with out of tree modules too (as Linux does), you would find much more support for that. 2) The GNU module guidelines should be followed. Namely, we should expect modules to declare their licenses and programmatically enforce license compatibility. 3) You should use glib's module loading API, not libdl 4) An explicitly insmod command should be used to load modules. Module dependency is very complicated. It's easier to just load modules in a specific order based on a configuration file. There are very useful reasons to have modules in QEMU. I really think Spice support would make sense as a module, for instance. libspice has a lot of dependencies and forcing distros to set those dependencies as dependencies on QEMU really stinks. So there's pretty good use-cases for in-tree modules. It's definitely worth doing. It's also pretty useful when doing security certifications. Regards, Anthony Liguori > > Example Makefile for out of tree modules: > #v+ > DEVICENAME=pcnet2 > > hw-obj-y=pcnet-pci.o > hw-obj-y+=pcnet.o > > include rules.mak > > .PHONY: all > > QEMU_CFLAGS=-I../qemu-kvm -I../qemu-kvm/hw > QEMU_CFLAGS+=-I../qemu-kvm/fpu -I../qemu-kvm/include > QEMU_CFLAGS+=-I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include > > QEMU_CFLAGS+=-DTARGET_PHYS_ADDR_BITS=64 -fPIC > LDFLAGS+=-shared > > LIBNAME=libqemu_$(DEVICENAME).so > > all: $(LIBNAME) > > $(LIBNAME): $(hw-obj-y) > $(call LINK,$^) > > clean: > rm -f *.o > rm -f *.d > rm -f $(LIBNAME) > > # Include automatically generated dependency files > -include $(patsubst %.o, %.d, $(hw-obj-y)) > > #v- > > Signed-off-by: Dominik Żeromski <dzeromsk@gmail.com> > --- > Makefile.target | 4 +++- > hw/qdev-monitor.c | 11 +++++++++++ > 2 files changed, 14 insertions(+), 1 deletions(-) > > diff --git a/Makefile.target b/Makefile.target > index 74f7a4a..7fd9245 100644 > --- a/Makefile.target > +++ b/Makefile.target > @@ -130,7 +130,9 @@ obj-$(CONFIG_HAVE_GET_MEMORY_MAPPING) += memory_mapping.o > obj-$(CONFIG_HAVE_CORE_DUMP) += dump.o > obj-$(CONFIG_NO_GET_MEMORY_MAPPING) += memory_mapping-stub.o > obj-$(CONFIG_NO_CORE_DUMP) += dump-stub.o > -LIBS+=-lz > +LIBS+=-lz -ldl > + > +LDFLAGS+=-rdynamic > > QEMU_CFLAGS += $(VNC_TLS_CFLAGS) > QEMU_CFLAGS += $(VNC_SASL_CFLAGS) > diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c > index 7915b45..3b5b0b0 100644 > --- a/hw/qdev-monitor.c > +++ b/hw/qdev-monitor.c > @@ -17,6 +17,8 @@ > * License along with this library; if not, see <http://www.gnu.org/licenses/>. > */ > > +#include <dlfcn.h> > + > #include "qdev.h" > #include "monitor.h" > #include "qmp-commands.h" > @@ -402,6 +404,8 @@ DeviceState *qdev_device_add(QemuOpts *opts) > const char *driver, *path, *id; > DeviceState *qdev; > BusState *bus; > + void *libhandle; > + char libname[NAME_MAX]; > > driver = qemu_opt_get(opts, "driver"); > if (!driver) { > @@ -419,7 +423,14 @@ DeviceState *qdev_device_add(QemuOpts *opts) > obj = object_class_by_name(driver); > } > } > + if (!obj) { > + snprintf(libname, sizeof(libname), "libqemu_%s.so", driver); > > + libhandle = dlopen(libname, RTLD_NOW); > + if (libhandle != NULL) { > + obj = object_class_by_name(driver); > + } > + } > if (!obj) { > qerror_report(QERR_INVALID_PARAMETER_VALUE, "driver", "device type"); > return NULL; > -- > 1.7.0.4
diff --git a/Makefile.target b/Makefile.target index 74f7a4a..7fd9245 100644 --- a/Makefile.target +++ b/Makefile.target @@ -130,7 +130,9 @@ obj-$(CONFIG_HAVE_GET_MEMORY_MAPPING) += memory_mapping.o obj-$(CONFIG_HAVE_CORE_DUMP) += dump.o obj-$(CONFIG_NO_GET_MEMORY_MAPPING) += memory_mapping-stub.o obj-$(CONFIG_NO_CORE_DUMP) += dump-stub.o -LIBS+=-lz +LIBS+=-lz -ldl + +LDFLAGS+=-rdynamic QEMU_CFLAGS += $(VNC_TLS_CFLAGS) QEMU_CFLAGS += $(VNC_SASL_CFLAGS) diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c index 7915b45..3b5b0b0 100644 --- a/hw/qdev-monitor.c +++ b/hw/qdev-monitor.c @@ -17,6 +17,8 @@ * License along with this library; if not, see <http://www.gnu.org/licenses/>. */ +#include <dlfcn.h> + #include "qdev.h" #include "monitor.h" #include "qmp-commands.h" @@ -402,6 +404,8 @@ DeviceState *qdev_device_add(QemuOpts *opts) const char *driver, *path, *id; DeviceState *qdev; BusState *bus; + void *libhandle; + char libname[NAME_MAX]; driver = qemu_opt_get(opts, "driver"); if (!driver) { @@ -419,7 +423,14 @@ DeviceState *qdev_device_add(QemuOpts *opts) obj = object_class_by_name(driver); } } + if (!obj) { + snprintf(libname, sizeof(libname), "libqemu_%s.so", driver); + libhandle = dlopen(libname, RTLD_NOW); + if (libhandle != NULL) { + obj = object_class_by_name(driver); + } + } if (!obj) { qerror_report(QERR_INVALID_PARAMETER_VALUE, "driver", "device type"); return NULL;
Adding support for loading DSO with -device option. Example Makefile for out of tree modules: #v+ DEVICENAME=pcnet2 hw-obj-y=pcnet-pci.o hw-obj-y+=pcnet.o include rules.mak .PHONY: all QEMU_CFLAGS=-I../qemu-kvm -I../qemu-kvm/hw QEMU_CFLAGS+=-I../qemu-kvm/fpu -I../qemu-kvm/include QEMU_CFLAGS+=-I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include QEMU_CFLAGS+=-DTARGET_PHYS_ADDR_BITS=64 -fPIC LDFLAGS+=-shared LIBNAME=libqemu_$(DEVICENAME).so all: $(LIBNAME) $(LIBNAME): $(hw-obj-y) $(call LINK,$^) clean: rm -f *.o rm -f *.d rm -f $(LIBNAME) # Include automatically generated dependency files -include $(patsubst %.o, %.d, $(hw-obj-y)) #v- Signed-off-by: Dominik Żeromski <dzeromsk@gmail.com> --- Makefile.target | 4 +++- hw/qdev-monitor.c | 11 +++++++++++ 2 files changed, 14 insertions(+), 1 deletions(-)