>-----Original Message-----
>From: Michael S. Tsirkin <m...@redhat.com>
>Subject: Re: [PATCH v2] intel_iommu: Introduce property "x-stale-tm" to control
>Transient Mapping (TM) field
>
>On Thu, Oct 17, 2024 at 07:57:53AM +0000, Duan, Zhenzhong wrote:
>>
>>
>> >-----Original Message-----
>> >From: Jason Wang <jasow...@redhat.com>
>> >Subject: Re: [PATCH v2] intel_iommu: Introduce property "x-stale-tm" to
>control
>> >Transient Mapping (TM) field
>> >
>> >On Thu, Oct 10, 2024 at 3:57 PM Zhenzhong Duan
><zhenzhong.d...@intel.com>
>> >wrote:
>> >>
>> >> VT-d spec removed Transient Mapping (TM) field from second-level page-
>tables
>> >> and treat the field as Reserved(0) since revision 3.2.
>> >>
>> >> Changing the field as reserved(0) will break backward compatibility, so
>> >> introduce a property "x-stale-tm" to allow user to control the setting.
>> >
>> >Nit: I think we probably don't need the x prefix? As we try to
>> >maintain the compatibility via:
>> >
>> >> + { TYPE_INTEL_IOMMU_DEVICE, "x-stale-tm", "on" },
>> >
>> >?
>>
>> I'm fine to remove it. But,
>> The prefix "x-" is used to indicate that a feature is experimental.
>
>No, it is used to indicate that the feature is not part of
>a stable API.
OK, Transient Mapping (TM) was removed in spec since 2020,
so I will remove "x-" then. Thanks for confirming.
BRs.
Zhenzhong
>
>> Couldn't we have a property both experimental and compatible?
>> I see a lot of such properties:
>>
>> # grep "x-" /sdb/qemu/hw/i386/pc.c
>> { "ICH9-LPC", "x-smi-swsmi-timer", "off" },
>> { "ICH9-LPC", "x-smi-periodic-timer", "off" },
>> { TYPE_INTEL_IOMMU_DEVICE, "x-stale-tm", "on" },
>> { TYPE_X86_CPU, "x-amd-topoext-features-only", "false" },
>> { TYPE_X86_CPU, "x-l1-cache-per-thread", "false" },
>> { "ICH9-LPC", "x-keep-pci-slot-hpc", "false" },
>> { TYPE_X86_CPU, "x-vendor-cpuid-only", "off" },
>> { "ICH9-LPC", "x-keep-pci-slot-hpc", "true" },
>> { "ICH9-LPC", "x-smi-cpu-hotunplug", "off" },
>> { "ICH9-LPC", "x-smi-cpu-hotplug", "off" },
>> { TYPE_X86_CPU, "x-intel-pt-auto-level", "off" },
>> { TYPE_X86_CPU, "x-hv-synic-kvm-only", "on" },
>> { TYPE_X86_CPU, "x-migrate-smi-count", "off" },
>> { TYPE_X86_CPU, "x-hv-max-vps", "0x40" },
>> { "i440FX-pcihost", "x-pci-hole64-fix", "off" },
>> { "q35-pcihost", "x-pci-hole64-fix", "off" },
>> { "kvmclock", "x-mach-use-reliable-get-clock", "off" },
>> { "ICH9-LPC", "x-smi-broadcast", "off" },
>>
>> Thanks
>> Zhenzhong
