From: "Michael S. Tsirkin" <mst@redhat.com>
To: "Duan, Zhenzhong" <zhenzhong.duan@intel.com>
Cc: "Jason Wang" <jasowang@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"Peng, Chao P" <chao.p.peng@intel.com>,
"Liu, Yi L" <yi.l.liu@intel.com>,
"Clément Mathieu--Drif" <clement.mathieu--drif@eviden.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Eduardo Habkost" <eduardo@habkost.net>,
"Marcel Apfelbaum" <marcel.apfelbaum@gmail.com>
Subject: Re: [PATCH v2] intel_iommu: Introduce property "x-stale-tm" to control Transient Mapping (TM) field
Date: Sat, 19 Oct 2024 20:25:01 -0400 [thread overview]
Message-ID: <20241019202416-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <SJ0PR11MB6744C0B9DE8D32354242099992472@SJ0PR11MB6744.namprd11.prod.outlook.com>
On Thu, Oct 17, 2024 at 07:57:53AM +0000, Duan, Zhenzhong wrote:
>
>
> >-----Original Message-----
> >From: Jason Wang <jasowang@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.duan@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.
> 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
next prev parent reply other threads:[~2024-10-20 0:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-10 7:53 [PATCH v2] intel_iommu: Introduce property "x-stale-tm" to control Transient Mapping (TM) field Zhenzhong Duan
2024-10-17 7:03 ` Jason Wang
2024-10-17 7:57 ` Duan, Zhenzhong
2024-10-18 4:30 ` Jason Wang
2024-10-20 0:25 ` Michael S. Tsirkin [this message]
2024-10-22 7:13 ` Duan, Zhenzhong
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