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From: | Marcel Apfelbaum |
Subject: | Re: [Qemu-devel] [PATCH] hostmem: Fix qemu_opt_get_bool() crash in host_memory_backend_init() |
Date: | Mon, 20 Jul 2015 23:06:01 +0300 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
On 07/20/2015 11:03 PM, Eduardo Habkost wrote:
On Mon, Jul 20, 2015 at 09:06:28AM +0200, Igor Mammedov wrote:On Fri, 17 Jul 2015 17:33:55 -0300 Eduardo Habkost <address@hidden> wrote:On Thu, Jul 16, 2015 at 11:02:14PM +0200, Igor Mammedov wrote:On Thu, 16 Jul 2015 17:39:17 -0300 Eduardo Habkost <address@hidden> wrote:This fixes the following crash, introduced by commit 49d2e648e8087d154d8bf8b91f27c8e05e79d5a6: $ gdb --args qemu-system-x86_64 -machine pc,mem-merge=off -object memory-backend-ram,id=ram-node0,size=1024 [...] Program received signal SIGABRT, Aborted. (gdb) bt #0 0x00007ffff253b8c7 in raise () at /lib64/libc.so.6 #1 0x00007ffff253d52a in abort () at /lib64/libc.so.6 #2 0x00007ffff253446d in __assert_fail_base () at /lib64/libc.so.6 #3 0x00007ffff2534522 in () at /lib64/libc.so.6 #4 0x00005555558bb80a in qemu_opt_get_bool_helper (opts=0x55555621b650, address@hidden "mem-merge", address@hidden, address@hidden) at qemu/util/qemu-option.c:388 #5 0x00005555558bbb5a in qemu_opt_get_bool (opts=<optimized out>, address@hidden "mem-merge", address@hidden) at qemu/util/qemu-option.c:398 #6 0x0000555555720a24 in host_memory_backend_init (obj=0x5555562ac970) at qemu/backends/hostmem.c:226 Instead of using qemu_opt_get_bool(), that didn't work with qemu_machine_opts for a long time, we can use the machine QOM properties directly. Signed-off-by: Eduardo Habkost <address@hidden> --- backends/hostmem.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/backends/hostmem.c b/backends/hostmem.c index 61c1ac0..38a32ed 100644 --- a/backends/hostmem.c +++ b/backends/hostmem.c @@ -10,6 +10,7 @@ * See the COPYING file in the top-level directory. */ #include "sysemu/hostmem.h" +#include "hw/boards.h" #include "qapi/visitor.h" #include "qapi-types.h" #include "qapi-visit.h" @@ -223,10 +224,10 @@ static void host_memory_backend_init(Object *obj) { HostMemoryBackend *backend = MEMORY_BACKEND(obj); - backend->merge = qemu_opt_get_bool(qemu_get_machine_opts(), - "mem-merge", true); - backend->dump = qemu_opt_get_bool(qemu_get_machine_opts(), - "dump-guest-core", true); + backend->merge = object_property_get_bool(OBJECT(current_machine),maybe use qdev_get_machine() instead of OBJECT(current_machine)What are the advantages you see in the extra layers of indirection of qdev_get_machine()? (I am not against your proposal, but I would like to understand the point of qdev_get_machine() yet.)current_machine might be NULL where as qdev_get_machine() always returns /machine object.In this case, I don't want "/machine" to be created as a generic container object by accident because it must be a MachineState object. If /machine is not initialized yet, that code should abort instead of trying to continue. But that can be solved by simply ensuring qdev_get_machine() is a TYPE_MACHINE object (see below).I'd prefer to use something that is guaranteed to be MachineState*, qdev_get_machine() returns Object*. I am even considering using current_machine->mem_merge and current_machine->dump_guest_core directly instead of object_property_get_bool(). That would mean extra compile-time checks, instead of runtime ones.Check difference 'git grep qdev_get_machine' vs 'git grep current_machine'. I was under impression that policy was trying no to use globals unless one has to, and not introduce new usage in presence of other means to get object.I will send a new version using: MachineState *machine = MACHINE(qdev_get_machine()); backend->merge = machine_mem_merge(machine); backend->dump = machine_dump_guest_core(machine); Then we have no global variable, type safety, and no direct access to struct fields.
+1 I am considering retiring curent_machine global variable for 2.5. Thanks, Marcel
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