Re: [RFC PATCH v2 0/4] vfio/pci: Atomic Ops completer support

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Markus, Marc-André,

> On 1/6/23 00:24, Alex Williamson wrote:
>> Policy decisions like that are generally left to management tools, so
>> there would always be a means to enable or disable the feature.  In
>> fact, that's specifically why I test that the Atomic Op completer bits
>> are unset in the root port before changing them so that this automatic
>> enablement could live alongside a command line option to statically
>> enable some bits.
>>
>> That does however remind me that it is often good with these sorts of
>> "clever" automatic features to have an opt-out, so I'll likely add an
>> x-no-rp-atomics device option in the next version to provide that.

Still thinking about this series I remembered since commit a3c45b3e62
("qapi: New special feature flag "unstable"") the "x-" prefix is
obsolete (superseded) in QAPI generated code.

I wonder about device properties:

$ git grep -F '"x-' hw | wc -l
      130

$ git grep -F '"x-' hw/vfio/pci.c
hw/vfio/pci.c:2987:        error_setg(errp, "x-balloon-allowed only 
potentially compatible "
hw/vfio/pci.c:3335: 
DEFINE_PROP_ON_OFF_AUTO("x-pre-copy-dirty-page-tracking", VFIOPCIDevice,
hw/vfio/pci.c:3342:    DEFINE_PROP_UINT32("x-intx-mmap-timeout-ms", 
VFIOPCIDevice,
hw/vfio/pci.c:3344:    DEFINE_PROP_BIT("x-vga", VFIOPCIDevice, features,
hw/vfio/pci.c:3346:    DEFINE_PROP_BIT("x-req", VFIOPCIDevice, features,
hw/vfio/pci.c:3348:    DEFINE_PROP_BIT("x-igd-opregion", VFIOPCIDevice, 
features,
hw/vfio/pci.c:3350:    DEFINE_PROP_BOOL("x-enable-migration", VFIOPCIDevice,
hw/vfio/pci.c:3352:    DEFINE_PROP_BOOL("x-no-mmap", VFIOPCIDevice, 
vbasedev.no_mmap, false),
hw/vfio/pci.c:3353:    DEFINE_PROP_BOOL("x-balloon-allowed", VFIOPCIDevice,
hw/vfio/pci.c:3355:    DEFINE_PROP_BOOL("x-no-kvm-intx", VFIOPCIDevice, 
no_kvm_intx, false),
hw/vfio/pci.c:3356:    DEFINE_PROP_BOOL("x-no-kvm-msi", VFIOPCIDevice, 
no_kvm_msi, false),
hw/vfio/pci.c:3357:    DEFINE_PROP_BOOL("x-no-kvm-msix", VFIOPCIDevice, 
no_kvm_msix, false),
hw/vfio/pci.c:3358:    DEFINE_PROP_BOOL("x-no-geforce-quirks", 
VFIOPCIDevice,
hw/vfio/pci.c:3360:    DEFINE_PROP_BOOL("x-no-kvm-ioeventfd", 
VFIOPCIDevice, no_kvm_ioeventfd,
hw/vfio/pci.c:3362:    DEFINE_PROP_BOOL("x-no-vfio-ioeventfd", 
VFIOPCIDevice, no_vfio_ioeventfd,
hw/vfio/pci.c:3364:    DEFINE_PROP_UINT32("x-pci-vendor-id", 
VFIOPCIDevice, vendor_id, PCI_ANY_ID),
hw/vfio/pci.c:3365:    DEFINE_PROP_UINT32("x-pci-device-id", 
VFIOPCIDevice, device_id, PCI_ANY_ID),
hw/vfio/pci.c:3366:    DEFINE_PROP_UINT32("x-pci-sub-vendor-id", 
VFIOPCIDevice,
hw/vfio/pci.c:3368:    DEFINE_PROP_UINT32("x-pci-sub-device-id", 
VFIOPCIDevice,
hw/vfio/pci.c:3370:    DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, 
igd_gms, 0),
hw/vfio/pci.c:3371: 
DEFINE_PROP_UNSIGNED_NODEFAULT("x-nv-gpudirect-clique", VFIOPCIDevice,
hw/vfio/pci.c:3374:    DEFINE_PROP_OFF_AUTO_PCIBAR("x-msix-relocation", 
VFIOPCIDevice, msix_relo,

Is there a plan to use something similar for QOM properties?
Is it OK to keep using the "x-" prefix there?

Thanks,

Phil.