Re: [Qemu-devel] [PULL 22/27] vl: Create block backends before setting machine properties

[Markus Armbruster <armbru@redhat.com>]

Michal Privoznik <mprivozn@redhat.com> writes:

> On 3/11/19 11:08 PM, Markus Armbruster wrote:
>> qemu-system-FOO's main() acts on command line arguments in its own
>> idiosyncratic order.  There's not much method to its madness.
>> Whenever we find a case where one kind of command line argument needs
>> to refer to something created for another kind later, we rejigger the
>> order.
>>
>> Block devices get created long after machine properties get processed.
>> Therefore, block device machine properties can be created, but not
>> set.  No such properties exist.  But the next commit will create some.
>> Time to rejigger again: create block devices earlier.
>>
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> Message-Id: <20190308131445.17502-8-armbru@redhat.com>
>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>> ---
>>   vl.c | 9 +++++++--
>>   1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/vl.c b/vl.c
>> index c22ca447fa..e9239d55ad 100644
>> --- a/vl.c
>> +++ b/vl.c
>> @@ -4274,6 +4274,13 @@ int main(int argc, char **argv, char **envp)
>>           exit(0);
>>       }
>>   +    /*
>> +     * Note: we need to create block backends before
>> +     * machine_set_property(), so machine properties can refer to
>> +     * them.
>> +     */
>> +    configure_blockdev(&bdo_queue, machine_class, snapshot);
>> +
>>       machine_opts = qemu_get_machine_opts();
>>       qemu_opt_foreach(machine_opts, machine_set_property, current_machine,
>>                        &error_fatal);
>> @@ -4400,8 +4407,6 @@ int main(int argc, char **argv, char **envp)
>>       ram_mig_init();
>>       dirty_bitmap_mig_init();
>>   -    configure_blockdev(&bdo_queue, machine_class, snapshot);
>> -
>>       qemu_opts_foreach(qemu_find_opts("mon"),
>>                         mon_init_func, NULL, &error_fatal);
>>   
>>
>
> Actually, there is more problems with this. Trying to run a guest with
> persistent reservations fails after this patch is applied (git bisect
> points me to this commit). My command line is:
>
> qemu.git $ ./x86_64-softmmu/qemu-system-x86_64 \
> -monitor stdio \
> -object pr-manager-helper,id=pr-helper0,path=/tmp/pr-helper0.sock
> -drive
> file=/dev/mapper/crypt,file.pr-manager=pr-helper0,format=raw,if=none,id=drive-scsi0-0-0-2 
> \
> -device
> scsi-block,bus=scsi0.0,channel=0,scsi-id=0,lun=2,drive=drive-scsi0-0-0-2,id=scsi0-0-0-2
>
> Honestly, I have no idea how to fix it, so I'm just raising this issue
> here. Do you want me to open a bug or something?

Let's skip the bug filing bureaucracy and go straight to debugging.

Actual and expected behavior of your reproducer, please :)