[RFC] qemu: Check for changes in qemu modules directory

[Jim Fehlig]

On 8/26/20 3:31 AM, Daniel P. Berrangé wrote:
> On Thu, Aug 20, 2020 at 05:03:44PM -0600, Jim Fehlig wrote:
>> Add a configuration option for specifying location of the qemu modules
>> directory, defaulting to /usr/lib64/qemu. Then use this location to
>> check for changes in the directory, indicating that a qemu module has
>> changed and capabilities need to be reprobed.
>>
>> Signed-off-by: Jim Fehlig <jfehlig at suse.com>
>> ---
>>
>> This is a mildly tested impl of the idea discussed here (and elsewhere
>> in the thread)
>>
>> https://www.redhat.com/archives/libvir-list/2020-August/msg00684.html
>>
>> I've checked that both system and session caches are updated when a
>> qemu modules package is updated. I'll do some more testing but wanted
>> to send the patch for early comments. Testing in other environments
>> would be much appreciated. Thanks!
>>
>>   meson.build                  |  6 ++++++
>>   meson_options.txt            |  1 +
>>   src/qemu/qemu_capabilities.c | 35 +++++++++++++++++++++++++++++++++++
>>   3 files changed, 42 insertions(+)
>>
>> diff --git a/meson.build b/meson.build
>> index a72d0c0e85..16928482aa 100644
>> --- a/meson.build
>> +++ b/meson.build
>> @@ -1745,6 +1745,12 @@ if not get_option('driver_qemu').disabled()
>>     if use_qemu
>>       conf.set('WITH_QEMU', 1)
>>   
>> +    qemu_moddir = get_option('qemu_moddir')
>> +    if qemu_moddir == ''
>> +      qemu_moddir = '/usr/lib64/qemu'
> 
> We sholdn't hardcode lib64 - use  libdir variable, eg
> 
> "/usr" / libdir / "qemu"

Good point. I've squashed in the below diff. While testing it I remembered to 
also test specifying the option, e.g. meson configure 
-Dqemu_moddir=/var/run/qemu/modules


diff --git a/meson.build b/meson.build
index 928f6a0bad..70a33cf5e4 100644
--- a/meson.build
+++ b/meson.build
@@ -1760,7 +1760,7 @@ if not get_option('driver_qemu').disabled()

      qemu_moddir = get_option('qemu_moddir')
      if qemu_moddir == ''
-      qemu_moddir = '/usr/lib64/qemu'
+      qemu_moddir = '/usr' / libdir / 'qemu'
      endif
      conf.set_quoted('QEMU_MODDIR', qemu_moddir)


> Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>

Thanks. I see we've entered freeze for 6.7.0. I'll wait until after the release 
before pushing this and the xen PCI permissive patches you reviewed.

Regards,
Jim