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From: Sean Christopherson <seanjc@google.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Jonathan Corbet <corbet@lwn.net>,
	 Shuah Khan <skhan@linuxfoundation.org>,
	Thomas Gleixner <tglx@kernel.org>,
	 Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	 Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org,  "H. Peter Anvin" <hpa@zytor.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Juergen Gross <jgross@suse.com>,
	 Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Paul Durrant <paul@xen.org>,  Jonathan Cameron <jic23@kernel.org>,
	Sascha Bischoff <Sascha.Bischoff@arm.com>,
	 Marc Zyngier <maz@kernel.org>, Joey Gouly <joey.gouly@arm.com>,
	Jack Allister <jalliste@amazon.com>,
	 Dongli Zhang <dongli.zhang@oracle.com>,
	joe.jin@oracle.com, kvm@vger.kernel.org,
	 linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	 xen-devel@lists.xenproject.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v7 05/36] KVM: x86: Fold __get_kvmclock() into get_kvmclock()
Date: Tue, 28 Jul 2026 16:06:09 -0700	[thread overview]
Message-ID: <amk14dmn5j7Oov1B@google.com> (raw)
In-Reply-To: <20260728144954.355376-6-dwmw2@infradead.org>

On Tue, Jul 28, 2026, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> There is no need for the separate __get_kvmclock() helper; just inline
> its body into get_kvmclock() within the seqcount retry loop.

Actually, there ends up being quite a bit of value if we rework the inner helper
to be all about the master clock mode.  If we go that route, then the main loop
is pretty self-explanatory, we can use early returns instead of continues and
subtle fall-throughs, and the indentation levels go down.

	do {
		data->flags = 0;

		seq = read_seqcount_begin(&ka->pvclock_sc);
		if (!__get_kvmclock_master_clock(kvm, data))
			data->clock = get_kvmclock_base_ns() + ka->kvmclock_offset;
	} while (read_seqcount_retry(&ka->pvclock_sc, seq));

  reply	other threads:[~2026-07-28 23:06 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-28 14:39 [PATCH v7 00/36] Cleaning up the KVM clock mess David Woodhouse
2026-07-28 14:39 ` [PATCH v7 01/36] KVM: x86: Improve accuracy of KVM clock when TSC scaling is in force David Woodhouse
2026-07-28 14:39 ` [PATCH v7 02/36] KVM: x86: Explicitly disable TSC scaling without CONSTANT_TSC David Woodhouse
2026-07-28 14:39 ` [PATCH v7 03/36] KVM: x86: Activate master clock immediately on vCPU creation David Woodhouse
2026-07-28 14:39 ` [PATCH v7 04/36] KVM: x86: Avoid NTP frequency skew for KVM clock on 32-bit host David Woodhouse
2026-07-28 14:39 ` [PATCH v7 05/36] KVM: x86: Fold __get_kvmclock() into get_kvmclock() David Woodhouse
2026-07-28 23:06   ` Sean Christopherson [this message]
2026-07-28 14:39 ` [PATCH v7 06/36] KVM: x86: Drop CPU pinning in get_kvmclock() David Woodhouse
2026-07-28 14:39 ` [PATCH v7 07/36] KVM: x86: Restructure get_kvmclock() David Woodhouse
2026-07-28 23:04   ` Sean Christopherson
2026-07-28 14:39 ` [PATCH v7 08/36] KVM: x86: Fix KVM clock precision in get_kvmclock() with TSC scaling David Woodhouse
2026-07-28 14:39 ` [PATCH v7 09/36] KVM: x86: Use get_kvmclock() in kvm_get_wall_clock_epoch() David Woodhouse
2026-07-28 14:39 ` [PATCH v7 10/36] KVM: x86: Fix compute_guest_tsc() to handle negative time deltas David Woodhouse
2026-07-28 14:39 ` [PATCH v7 11/36] KVM: x86: Restructure kvm_guest_time_update() for TSC upscaling David Woodhouse
2026-07-28 14:39 ` [PATCH v7 12/36] KVM: x86: Simplify and comment kvm_get_time_scale() David Woodhouse
2026-07-28 14:39 ` [PATCH v7 13/36] KVM: x86: Remove implicit rdtsc() from kvm_compute_l1_tsc_offset() David Woodhouse
2026-07-28 14:39 ` [PATCH v7 14/36] KVM: x86: Improve synchronization in kvm_synchronize_tsc() David Woodhouse
2026-07-28 14:39 ` [PATCH v7 15/36] KVM: x86: Kill last_tsc_{nsec,write,offset} fields David Woodhouse
2026-07-28 14:39 ` [PATCH v7 16/36] KVM: x86: Replace nr_vcpus_matched_tsc count with all_vcpus_matched_tsc bool David Woodhouse
2026-07-28 14:39 ` [PATCH v7 17/36] KVM: x86: Allow KVM master clock mode when TSCs are offset from each other David Woodhouse
2026-07-28 14:39 ` [PATCH v7 18/36] KVM: x86: Factor out kvm_use_master_clock() David Woodhouse
2026-07-28 14:39 ` [PATCH v7 19/36] KVM: x86: Avoid gratuitous global clock updates David Woodhouse
2026-07-28 14:40 ` [PATCH v7 20/36] KVM: x86/xen: Prevent runstate times from becoming negative David Woodhouse
2026-07-28 14:40 ` [PATCH v7 21/36] KVM: x86: Avoid redundant masterclock updates from multiple vCPUs David Woodhouse
2026-07-28 14:40 ` [PATCH v7 22/36] KVM: x86: Remove runtime Xen TSC frequency CPUID update David Woodhouse
2026-07-28 14:40 ` [PATCH v7 23/36] KVM: x86: Re-synchronize TSC after KVM_SET_TSC_KHZ David Woodhouse
2026-07-28 14:40 ` [PATCH v7 24/36] KVM: x86: Use ktime_get_snapshot_id() for master clock David Woodhouse
2026-07-28 14:40 ` [PATCH v7 25/36] KVM: x86: Compute kvmclock base without pvclock_gtod_data David Woodhouse
2026-07-28 14:40 ` [PATCH v7 26/36] KVM: x86: Cache host vclock_mode for masterclock eligibility checks David Woodhouse
2026-07-28 14:40 ` [PATCH v7 27/36] KVM: x86: Remove pvclock_gtod_data and private timekeeping code David Woodhouse
2026-07-28 14:40 ` [PATCH v7 28/36] KVM: x86: Activate master clock from kvm_arch_init_vm() David Woodhouse
2026-07-28 14:40 ` [PATCH v7 29/36] UAPI: x86: Move pvclock-abi to UAPI for x86 platforms David Woodhouse
2026-07-28 14:40 ` [PATCH v7 30/36] KVM: selftests: Use UAPI pvclock-abi.h in xen_shinfo_test David Woodhouse
2026-07-28 14:40 ` [PATCH v7 31/36] KVM: x86: Add KVM_[GS]ET_CLOCK_GUEST for accurate KVM clock migration David Woodhouse
2026-07-28 14:40 ` [PATCH v7 32/36] KVM: x86: Add KVM_VCPU_TSC_SCALE and fix the documentation on TSC migration David Woodhouse
2026-07-28 14:40 ` [PATCH v7 33/36] KVM: selftests: Add KVM/PV clock selftest to prove timer correction David Woodhouse
2026-07-28 14:40 ` [PATCH v7 34/36] KVM: selftests: Add master clock offset test David Woodhouse
2026-07-28 14:40 ` [PATCH v7 35/36] KVM: selftests: Add Xen/generic CPUID timing leaf test David Woodhouse
2026-07-28 14:40 ` [PATCH v7 36/36] KVM: selftests: Add Xen runstate migration test David Woodhouse
2026-07-28 23:18 ` [PATCH v7 00/36] Cleaning up the KVM clock mess Sean Christopherson

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