From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 75EA444D01D for ; Wed, 26 Aug 2026 21:33:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787779986; cv=none; b=W1Nql+r6Brn4JFkKelftv4rSQwpKLx00tWES9ShOw3SWI/Gpvvr7RBIV1JA363M/phv6ln5FXLPkHARLZ2/UHs621FzmzCeEEmvZSNg+EAEIqDGO8rMxaYpMsyU/I1P3a5YBVEaXD0SkT7cronsNXrURARdCYACmPOkVJJjzUN8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787779986; c=relaxed/simple; bh=BpaksvF5UiW1hvchMik7kTD9xZb/ra4jb7djNqkMrks=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=QWM+6UIch2iiHjMTlUh1bu5MCEDNB+HzsiafL+WosISMBPWNg+UUN4pgpLaJ6pqiu2TjVBV0eAFJxNOBx8WV2zZQnM39xuW6JqyBBo55srjNU2bQozvpa/eOIQ4dD8ZSZ1aFlsE0jesPPOdQo0azh+arQsH5xRRWrN8k0hSYQzE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=nQ9ky1aV; arc=none smtp.client-ip=209.85.215.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nQ9ky1aV" Received: by mail-pg1-f198.google.com with SMTP id 41be03b00d2f7-c856470fe9fso1233238a12.2 for ; Wed, 26 Aug 2026 14:33:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1787779985; x=1788384785; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date :reply-to:from:to:cc:subject:date:message-id:reply-to:content-type; bh=4JrZ3+7VrlAoRWfokfGXF58q3ir4/R4tHcE9QWIU5G4=; b=nQ9ky1aVJWyFCarMJgy3yoCfgpEU9QPIZEhiSFSnn2Pl98SFEK+DrozErr7zzqgT0d 6ZtEclmeR4yh59GalSOq/iaA+birD067f9BUzh6LVSADxgafciY1olCKGNjF16BFox95 zypXppQyw7j6vUHEiRHn4dnnhO/6yjZ8StEuPWceqc3F57mVSlycxFUH+bHjc2oHRykT hNJi/7QdAHwPNjCc85c1um/i8SFXxZ1ErcVKPC73i5NL8vWTNFb3LVhj5W0DIr1wOKtA /TA2ycfNeKJ2WOie0LnxybAgd1yNQQX+TEAQ5Qapp0Vmzm5ZtcGboOBr1Xn2g28zEI+r cMTQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787779985; x=1788384785; h=content-type:cc:to:from:subject:message-id:mime-version:date :reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=4JrZ3+7VrlAoRWfokfGXF58q3ir4/R4tHcE9QWIU5G4=; b=lX0GuvS2F0di+mQWMHcyeBPMQsj2IbPHFcWigcgQqVTAgOKMawl0A0cgfO1ZWVSTPB yL0FtReKaYzowcd3CvtzOPQZa5Uv6KIds07E6Ses39kEuGEuPMhmmN95B+XWfj/oquW7 GxS7Mb713siVBTZYiSq+Cj6IJnnnuYU65XDOnzvrP9QkH2BEdc9DKrnV1xyLDxdKgJ9x t9beeCZlDp9oC/KXzkR3P2vD5CsP5/3j2q71j1MAplo0o/eNw1L90Fd7+zWzoxCa11lk Fft/cYdFpDuvNbdGGSM8XXhVJV4BY5bCVVyVu+t2smCQBPGAyfmFIeY3uNH9UjtT/ioc cxGA== X-Forwarded-Encrypted: i=1; AHgh+RrKdqACJkgoYbt4oxKtYuXBFcA3DpvlP++VFoFIXoo0bNE2nueaBt96Z8o68AL7MhH7HpZ/9C5gJii3IHg=@vger.kernel.org X-Gm-Message-State: AFuF++nDvus8oeawwaPUIHNKWyrdiK10XjUlOleIjSe0979wFiNDOy28 AiTr6p5vTz2bZnlcCe/aWg10EYmMtrLtStoFDwYhS4RT4NjIPhB5lBJ3kFQYuhIqVu1E8t1wOXe xXu52+w== X-Received: from pgby7-n1.prod.google.com ([2002:a05:6a02:6507:10b0:cbe:9e80:c38b]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:e18b:b0:3be:b0b3:3962 with SMTP id adf61e73a8af0-3cf83f36b8amr21365562637.9.1787779984471; Wed, 26 Aug 2026 14:33:04 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 26 Aug 2026 14:32:40 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.887.g758fc8c411-goog Message-ID: <20260826213303.914988-1-seanjc@google.com> Subject: [PATCH v10 00/21] KVM: x86: Cleaning up the KVM clock mess, part 1 From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Durrant , David Woodhouse , Dongli Zhang Content-Type: text/plain; charset="UTF-8" Part 1 of David's series to clean up the host-side mess of kvmclock. The cut point in this version is still quite arbitrary, but what's left for "part 2" fits nicely into 2-3 buckets: 1: Masterclock overhaul 2. New uAPI and tests v10: - Drop the stale reference to using div_u64() for the now-removed CPUID leaf. [Sashiko] - Don't bother with a enabling the pvclock_gtod notifier on 32-bit, and go straight to ktime_mono_to_any(). [Sashiko] v9: - https://lore.kernel.org/all/20260810225500.869288-1-seanjc@google.com - Pull in "Compute kvmclock base without pvclock_gtod_data" before "Avoid NTP frequency skew for KVM clock on 32-bit host" to avoid having to provide what is effectively an open-coded version of ktime_mono_to_any() to avoid data races. [Sashiko]. - Pull in use of kernel timekeeping snapshots, split in three patches purely to aid review and bisection. - Check and clear KVM_REQ_MASTERCLOCK_UPDATE in kvm_arch_vcpu_postcreate(). [me, Sashiko] - Add the missing return value in "Move "no master clock" fallback from...". [Sashiko] v8: - Obviously cut partway through the full series. - Update commit references for 633d7652f80f ("KVM: x86/xen: Do not corrupt KVM clock in kvm_xen_shared_info_init()"). - Chunk the "Restructure ..." patches into individual logical changes ("Restructure kvm_guest_time_update() for TSC upscaling" in particular was quite gnarly). - Ensure the TSC+freq pair during guest time updates happens on a single CPU. [Sashiko] - Keep __get_kvmclock() as a masterclock-specific helper to avoid deep indentation and gotos. - Do waaaaay too much spelunking to try piece together the history of some of the many warts. - Ensure preemption is disabled in get_kvmclock() when getting the TSC freq. v7: https://lore.kernel.org/all/20260728144954.355376-1-dwmw2@infradead.org David Woodhouse (14): KVM: x86: Improve accuracy of KVM clock when TSC scaling is in force KVM: x86: Explicitly disable TSC scaling without CONSTANT_TSC KVM: x86: Activate master clock immediately on vCPU creation KVM: x86: Compute kvmclock base without pvclock_gtod_data KVM: x86: Avoid NTP frequency skew for KVM clock on 32-bit host KVM: x86: Wrap all of __get_kvmclock_master_clock() with CONFIG_X86_64=y KVM: x86: Fall back to non-master-clock if clockread fails in get_kvmclock() KVM: x86: Fix KVM clock precision in get_kvmclock() with TSC scaling KVM: x86: Use get_kvmclock() in kvm_get_wall_clock_epoch() KVM: x86: Fix compute_guest_tsc() to handle negative time deltas KVM: x86: Upscale TSC to "now", not master clock when updating PV clocks KVM: x86: Simplify and comment kvm_get_time_scale() KVM: x86: Remove implicit rdtsc() from kvm_compute_l1_tsc_offset() KVM: x86: Use kernel timekeeping snapshots for getting kvmclock time since boot Sean Christopherson (7): KVM: x86: Update "last guest TSC" snapshot prior to enabling IRQs/preemption KVM: x86: Drop unnecessary CPU pinning when computing/getting kvmclock KVM: x86: Move "no master clock" fallback from __get_kvmclock() to get_kvmclock() KVM: x86: Disable preemption, not IRQs, when getting TSC+freq pair KVM: x86: Make master clock logic in guest PV clock updates 64-bit only KVM: x86: Use kernel timekeeping snapshot for monotonic clock KVM: x86: Use kernel timekeeping snapshot to get walltime+TSC arch/x86/include/asm/kvm_host.h | 6 +- arch/x86/kvm/cpuid.c | 1 + arch/x86/kvm/msrs.c | 3 +- arch/x86/kvm/svm/svm.c | 3 +- arch/x86/kvm/vmx/vmx.c | 10 + arch/x86/kvm/x86.c | 480 +++++++++++++++----------------- arch/x86/kvm/x86.h | 3 +- 7 files changed, 240 insertions(+), 266 deletions(-) base-commit: 76671054f9a1ff6abb976583cd8da37650acdc97 -- 2.55.0.887.g758fc8c411-goog