From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f199.google.com (mail-pg1-f199.google.com [209.85.215.199]) (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 D5C03381EA9 for ; Fri, 16 Oct 2026 04:44:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792125860; cv=none; b=PccRicCd6KFsCsw/cStZ/GVy8QXmtxgbfpXeoQ6Rw4S/+dRyj2fziwRx3suJQTnNClS2SMJbWhIy+1Wn/Bsp53UQLsue+Cgda7N24Otn2b45jOTzmLN0IQysuuDqEZtSNueLZAEMMaAG/HSLq7mL1QcdwEJ508YdEQJQI4GSVDw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792125860; c=relaxed/simple; bh=iBxhG0lDSXU9hccFsW+kLsVMxETbKXUFyCPAbKw24bg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=st62HT6E4kc4EChvqs2hlEM7OQ2H2f88Q4/kfgD3J3FerYGhHKfrS0sYbzqiBgEi95JCRmEIPQYf/xqHxee+QU1LRPvT7zap0CiQ81UZ+Ec7god/WmzOeg/dEwkmJGMNyQQLI+FDL2ey5YICh6S+mTdEsPH5q2bSWxrI6eQ2kpE= 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=rJsRHJde; arc=none smtp.client-ip=209.85.215.199 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="rJsRHJde" Received: by mail-pg1-f199.google.com with SMTP id 41be03b00d2f7-cd65285537aso267141a12.1 for ; Thu, 15 Oct 2026 21:44:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1792125858; x=1792730658; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:reply-to:from:to:cc:subject:date:message-id :reply-to:content-type; bh=stWvJXyBUg4KLELHwAAG+Vn93f0auxo1LLZDP1lXIio=; b=rJsRHJdeO12phGND+PhhDGk1cCcJyRFb0yAn/va1+H8kk1K/uWODl1bXSadrVTD1HS 3UWcC0wMzGnk376YjrkyBGaIYd2gCqcntYSwyzjPJxVfwgBDX0Rv11CB/NcS+So+5Xnf 9Wz29wX9/eaFtMq4h0icmmVq+X4b6ea00EKaQQAF/poRtot0OUQk699/CwoW/h64e97z bx422oNwQSrwsRgUauPkPXs3AunmzNu3ST52b6Lvkf3w3nl6qfOjDzS7JdOpoCjTxRcl wwYRcWsvTI+s9NBXH0KAB20hnfoJD/c1PuHgpZOLEdt+evG4TZxT/S7cnhi5GIgT3fUP KHEw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792125858; x=1792730658; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:reply-to:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to:content-type; bh=stWvJXyBUg4KLELHwAAG+Vn93f0auxo1LLZDP1lXIio=; b=wkOZ7atwfLV+o84JgT+cBYz9/Nfd46rwPHhJLKdPNelVENNHUozbueYY2X315yqSJX nFZcs6s3LEN21GNBBn1VSP0nJQSPADguCaNsfulO7c5AG7fycCmzbS6sQo4KOVgre/HK bqB/+ZStrBkCPO8OaDsf9z1+xz1gt2Yz/3U27aVWnQFnU9TrqIPo5xRKtv/k08yvlTNI 7Y2wxO1KxqNZzjkjnodfloDOS7vmsct3Ir1YJOfSxd3RcPkmDBpshmHRdIY0XIB63wy8 HYX5JtepZqpDe5PGecNQJ8TYncJo9ag3I67kVidW907iGShzwYngpfKYt9AH+IVvTrD5 1OYA== X-Forwarded-Encrypted: i=1; AKwUvBwElhtWRSGUiHZjmr0rv3BXMuO9fFyLHoiV5WLZ0FvA2le1MuFT8O4trdk9rN5ruuQPkZhtcLhDCP1Ik9Q=@vger.kernel.org X-Gm-Message-State: AFq9FYL/OoEA3yvjkOcuUWBt1G6xv4+q0AxsFHLwFZBmzXbN+o7AdE69 sC+oTYKS2DvQ/Y9WJXLhiKH5cxM1ezhoI0J0IPbfSOxSKT2TvLtSp+I65EOkCINtVIeMPIKL7a6 +PWu2xA== X-Received: from pgbq26.prod.google.com ([2002:a63:5c1a:0:b0:cc7:e0b2:a5a2]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:1015:b0:3e1:6acc:59ea with SMTP id adf61e73a8af0-3e16c093f8cmr17703333637.62.1792125857644; Thu, 15 Oct 2026 21:44:17 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 15 Oct 2026 21:44:06 -0700 In-Reply-To: <20261016044415.958618-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20261016044415.958618-1-seanjc@google.com> X-Mailer: git-send-email 2.56.0.176.g3575e65682-goog Message-ID: <20261016044415.958618-2-seanjc@google.com> Subject: [GIT PULL] KVM: x86: Timekeeping fixes+cleanups for 7.4 From: Sean Christopherson To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Christopherson Content-Type: text/plain; charset="UTF-8" Part 1 of 2 (or maybe 3) of David's war on kvmclock. Ugh, and when looking at the shortlog, I realized I botched the author on these: KVM: x86: Use kernel timekeeping snapshot for monotonic clock KVM: x86: Use kernel timekeeping snapshot to get walltime+TSC Holler if you would prefer a fixup to get the author right; these have been in -next for over a month, so I opted to send them as-is instead of doing a super last minute rewrite. The following changes since commit d4b7fb647204f0c81dfeae2d1a708e4d858e0c94: Merge branch 'kvm-xen-longmode' into HEAD (2026-09-04 17:35:03 +0200) are available in the Git repository at: https://github.com/kvm-x86/linux.git tags/kvm-x86-clocks-7.4 for you to fetch changes up to d7841275e1fb4ad1e1877e56725ebda5b6e3143d: KVM: x86: Use kernel timekeeping snapshot to get walltime+TSC (2026-09-11 11:46:19 -0700) ---------------------------------------------------------------- KVM x86 timekeeping fixes and cleanups for 7.4 Fix a variety of warts in KVM's handling of guest TSC, kvmclock, and timekeeping in general, as a (big) first step towards addressing several longstanding problems with the kvmclock implementation. Most notably, fix a precision issue where get_kvmclock_ns() computed the clock from the *host* TSC without applying guest TSC scaling, causing systemic drift from the values the guest computes from its own TSC. As a bonus cleanup, rip out the whole pvclock_gtod_data hack, which was shadowing the kernel's timekeeping, and use ktime snapshots. ---------------------------------------------------------------- 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(-)