From: Xiaoyao Li <xiaoyao.li@intel.com>
To: Zhao Liu <zhao1.liu@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Richard Henderson <richard.henderson@linaro.org>,
Eduardo Habkost <eduardo@habkost.net>,
"Michael S . Tsirkin" <mst@redhat.com>,
Marcel Apfelbaum <marcel.apfelbaum@gmail.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Igor Mammedov <imammedo@redhat.com>,
Tim Wiederhake <twiederh@redhat.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org,
Zhao Liu <zhao1.liu@intel.com>
Subject: Re: [PATCH for-9.1 0/7] target/i386/kvm: Cleanup the kvmclock feature name
Date: Wed, 24 Apr 2024 23:57:11 +0800 [thread overview]
Message-ID: <fb252e78-2e71-4422-9499-9eac69102eec@intel.com> (raw)
In-Reply-To: <20240329101954.3954987-1-zhao1.liu@linux.intel.com>
On 3/29/2024 6:19 PM, Zhao Liu wrote:
> From: Zhao Liu <zhao1.liu@intel.com>
>
> Hi list,
>
> This series is based on Paolo's guest_phys_bits patchset [1].
>
> Currently, the old and new kvmclocks have the same feature name
> "kvmclock" in FeatureWordInfo[FEAT_KVM].
>
> When I tried to dig into the history of this unusual naming and fix it,
> I realized that Tim was already trying to rename it, so I picked up his
> renaming patch [2] (with a new commit message and other minor changes).
>
> 13 years age, the same name was introduced in [3], and its main purpose
> is to make it easy for users to enable/disable 2 kvmclocks. Then, in
> 2012, Don tried to rename the new kvmclock, but the follow-up did not
> address Igor and Eduardo's comments about compatibility.
>
> Tim [2], not long ago, and I just now, were both puzzled by the naming
> one after the other.
The commit message of [3] said the reason clearly:
When we tweak flags involving this value - specially when we use "-",
we have to act on both.
So you are trying to change it to "when people want to disable kvmclock,
they need to use '-kvmclock,-kvmclock2' instead of '-kvmclock'"
IMHO, I prefer existing code and I don't see much value of
differentiating them. If the current code puzzles you, then we can add
comment to explain.
> So, this series is to push for renaming the new kvmclock feature to
> "kvmclock2" and adding compatibility support for older machines (PC 9.0
> and older).
>
> Finally, let's put an end to decades of doubt about this name.
>
>
> Next Step
> =========
>
> This series just separates the two kvmclocks from the naming, and in
> subsequent patches I plan to stop setting kvmclock(old kcmclock) by
> default as long as KVM supports kvmclock2 (new kvmclock).
No. It will break existing guests that use KVM_FEATURE_CLOCKSOURCE.
> Also, try to deprecate the old kvmclock in KVM side.
>
> [1]: https://lore.kernel.org/qemu-devel/20240325141422.1380087-1-pbonzini@redhat.com/
> [2]: https://lore.kernel.org/qemu-devel/20230908124534.25027-4-twiederh@redhat.com/
> [3]: https://lore.kernel.org/qemu-devel/1300401727-5235-3-git-send-email-glommer@redhat.com/
> [4]: https://lore.kernel.org/qemu-devel/1348171412-23669-3-git-send-email-Don@CloudSwitch.com/
>
> Thanks and Best Regards,
> Zhao
>
> ---
> Tim Wiederhake (1):
> target/i386: Fix duplicated kvmclock name in FEAT_KVM
>
> Zhao Liu (6):
> target/i386/kvm: Add feature bit definitions for KVM CPUID
> target/i386/kvm: Remove local MSR_KVM_WALL_CLOCK and
> MSR_KVM_SYSTEM_TIME definitions
> target/i386/kvm: Only Save/load kvmclock MSRs when kvmclock enabled
> target/i386/kvm: Save/load MSRs of new kvmclock
> (KVM_FEATURE_CLOCKSOURCE2)
> target/i386/kvm: Add legacy_kvmclock cpu property
> target/i386/kvm: Update comment in kvm_cpu_realizefn()
>
> hw/i386/kvm/clock.c | 5 ++--
> hw/i386/pc.c | 1 +
> target/i386/cpu.c | 3 +-
> target/i386/cpu.h | 32 +++++++++++++++++++++
> target/i386/kvm/kvm-cpu.c | 25 ++++++++++++++++-
> target/i386/kvm/kvm.c | 59 +++++++++++++++++++++++++--------------
> 6 files changed, 99 insertions(+), 26 deletions(-)
>
next prev parent reply other threads:[~2024-04-24 15:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-29 10:19 [PATCH for-9.1 0/7] target/i386/kvm: Cleanup the kvmclock feature name Zhao Liu
2024-03-29 10:19 ` [PATCH for-9.1 1/7] target/i386/kvm: Add feature bit definitions for KVM CPUID Zhao Liu
2024-04-24 11:25 ` Xiaoyao Li
2024-03-29 10:19 ` [PATCH for-9.1 2/7] target/i386/kvm: Remove local MSR_KVM_WALL_CLOCK and MSR_KVM_SYSTEM_TIME definitions Zhao Liu
2024-04-24 15:11 ` Xiaoyao Li
2024-03-29 10:19 ` [PATCH for-9.1 3/7] target/i386/kvm: Only Save/load kvmclock MSRs when kvmclock enabled Zhao Liu
2024-03-29 10:19 ` [PATCH for-9.1 4/7] target/i386/kvm: Save/load MSRs of new kvmclock (KVM_FEATURE_CLOCKSOURCE2) Zhao Liu
2024-03-29 10:19 ` [PATCH for-9.1 5/7] target/i386/kvm: Add legacy_kvmclock cpu property Zhao Liu
2024-03-29 10:19 ` [PATCH for-9.1 6/7] target/i386: Fix duplicated kvmclock name in FEAT_KVM Zhao Liu
2024-03-29 10:19 ` [PATCH for-9.1 7/7] target/i386/kvm: Update comment in kvm_cpu_realizefn() Zhao Liu
2024-04-24 10:33 ` [PATCH for-9.1 0/7] target/i386/kvm: Cleanup the kvmclock feature name Zhao Liu
2024-04-24 15:57 ` Xiaoyao Li [this message]
2024-04-25 7:17 ` Zhao Liu
2024-04-25 8:40 ` Xiaoyao Li
2024-04-25 10:29 ` Zhao Liu
2024-04-25 12:04 ` Xiaoyao Li
2024-04-25 13:36 ` Zhao Liu
2024-05-29 13:58 ` Zhao Liu
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