>-----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.
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
