From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) (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 9130A3B42CE for ; Mon, 10 Aug 2026 22:55:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786402531; cv=none; b=EKv9r9GtP9pI7iewUPs5d7nRiS7it37kiDe91L/OsENVB83FPJb1AxxzI3imHHp6zLLQFE7FVVn1E1DvpZsJFs1NjpPGQgx1R5kDmz1fVrt9UL1clg32/XUPuV59pog2l6sxbZcoIZgpEIVCeEjlhVbGnYs4KCXHG7ReUgdtd4s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786402531; c=relaxed/simple; bh=ezLJCLMbVJeO1TB2+TOYF2iKtaGrO11RtViA7rAPS+0=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=modTTM2BQBD7MGVpnnkWREzJYIevFyrLQy6IfFTm3AW7rz53LYoCP38CCy1BefsYXHpb7Mhim9Ma6rYABTKwbTWCc7oNHHcDCI4o9FuMtjpkFnZCmOEXcLaMpzfpzmi9nOIrqIfHiyK+lKXhgUbjdnijbbYxhK/WF6ADf5ij/WI= 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=K4p8qdpy; arc=none smtp.client-ip=209.85.210.198 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="K4p8qdpy" Received: by mail-pf1-f198.google.com with SMTP id d2e1a72fcca58-84865f326efso3032302b3a.0 for ; Mon, 10 Aug 2026 15:55:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1786402529; x=1787007329; 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=x+HTMJZ+MtQQgAVQxt+nrwT2irv/Xu9LPWilczsy7do=; b=K4p8qdpyCBfam/LuUqtgT50b+4rD41+yLmwkoZ3wP0bkEee99rzhYy1kV6iybuXAGo tr7gVtF9woD9SPM4Lucg3dWq1d63puaGwezATI/0fhW5zUZn3qKBLvWuEG8ON0CFVI3L X5AApxHwd0nEfqqNAXfI4B77XGzEBwk4JDZiF8eGcmOsid5IvJ7t2bSuD6W8NFIgOeRU nv+bUFxuQTDBbcRzp2od9/SLpJGTWrwCS9BrVWgo2/Oji6c34aUrHNDUjvl0X7cFWoOX 9j9XKsGvOwLSKJZYhFjazkNYveX5aVtRaFcsYtwDGW+8E4tto52+snDYtlri/2avJsTz kFmA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786402529; x=1787007329; 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=x+HTMJZ+MtQQgAVQxt+nrwT2irv/Xu9LPWilczsy7do=; b=JLBp1ebtrUpIAN154vrLA0jgPEdoSCGGOUy0cGWCAYVTc98llvpi4NaOLsfLpbw9jh CqjQd3/dJpMrszDmfgfCSxATf1btkpgyNC+4h5G378rufznub+QLVG3bTpb8G6R8D+7W ajbvWv/SPCCx+OFHkv8hwgKLFPPGEVOWSktg8jJtCpyZXoCK0gNLqVe/dCcp1Qaq2W6L YWGq3jQDX3IzIlnNhMltQe7l6zj8fCAAYnTVDRgEOBoElb+6GsKOt6GD9Xf4K6tPFl7x ZBKfuxAQo01oUj3VbDiRlZss8+Jxl4vdWdln7F0p4UjLYIuQGQ/+em9II0qwEkr/Tovb wPXQ== X-Gm-Message-State: AOJu0Yxo3DyMsYNIIiEP3r4CAranyzbGo6q/UyHVptJ1Vpke9GGkDVAn Cefblgh9rYh8dTtdDu1mlGSDOOLy7kpi6o42/fvC4mvEaNiOgwLlEA3EspqTm/fP3WQtfENojuj Xf3uJUg== X-Received: from pgv36.prod.google.com ([2002:a63:1564:0:b0:cbe:93b3:1154]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:1396:b0:845:eb88:3d74 with SMTP id d2e1a72fcca58-84f9c9d8504mr4998640b3a.29.1786402528485; Mon, 10 Aug 2026 15:55:28 -0700 (PDT) Reply-To: Sean Christopherson Date: Mon, 10 Aug 2026 15:54:59 -0700 In-Reply-To: <20260810225500.869288-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260810225500.869288-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.679.g6767b8d81c-goog Message-ID: <20260810225500.869288-22-seanjc@google.com> Subject: [PATCH v9 21/21] KVM: x86: Use kernel timekeeping snapshot to get walltime+TSC 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" Replace the KVM-private vgettsc()+/do_do_realtime() timekeeping reimplementation with calls to the recently crafted, generic ktime_get_snapshot_id() interface. As noted previously, the snapshot provides both the system time and the raw_cycles (TSC), atomically paired using a sequence counter. With great pleasure, delete the now unused read_tsc() and vgettsc() Signed-off-by: David Woodhouse [sean: separate from other conversions, express joy at vgettsc()'s demise] Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 85 ++++------------------------------------------ 1 file changed, 6 insertions(+), 79 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1513e4ae2353..a638898e528f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1381,82 +1381,6 @@ void kvm_synchronize_tsc(struct kvm_vcpu *vcpu, u64 *user_value) #ifdef CONFIG_X86_64 -static u64 read_tsc(void) -{ - u64 ret = (u64)rdtsc_ordered(); - u64 last = pvclock_gtod_data.clock.cycle_last; - - if (likely(ret >= last)) - return ret; - - /* - * GCC likes to generate cmov here, but this branch is extremely - * predictable (it's just a function of time and the likely is - * very likely) and there's a data dependence, so force GCC - * to generate a branch instead. I don't barrier() because - * we don't actually need a barrier, and if this function - * ever gets inlined it will generate worse code. - */ - asm volatile (""); - return last; -} - -static inline u64 vgettsc(struct pvclock_clock *clock, u64 *tsc_timestamp, - int *mode) -{ - u64 tsc_pg_val; - long v; - - switch (clock->vclock_mode) { - case VDSO_CLOCKMODE_HVCLOCK: - if (hv_read_tsc_page_tsc(hv_get_tsc_page(), - tsc_timestamp, &tsc_pg_val)) { - /* TSC page valid */ - *mode = VDSO_CLOCKMODE_HVCLOCK; - v = (tsc_pg_val - clock->cycle_last) & - clock->mask; - } else { - /* TSC page invalid */ - *mode = VDSO_CLOCKMODE_NONE; - } - break; - case VDSO_CLOCKMODE_TSC: - *mode = VDSO_CLOCKMODE_TSC; - *tsc_timestamp = read_tsc(); - v = (*tsc_timestamp - clock->cycle_last) & - clock->mask; - break; - default: - *mode = VDSO_CLOCKMODE_NONE; - } - - if (*mode == VDSO_CLOCKMODE_NONE) - *tsc_timestamp = v = 0; - - return v * clock->mult; -} - -static int do_realtime(struct timespec64 *ts, u64 *tsc_timestamp) -{ - struct pvclock_gtod_data *gtod = &pvclock_gtod_data; - unsigned long seq; - int mode; - u64 ns; - - do { - seq = read_seqcount_begin(>od->seq); - ts->tv_sec = gtod->wall_time_sec; - ns = gtod->clock.base_cycles; - ns += vgettsc(>od->clock, tsc_timestamp, &mode); - ns >>= gtod->clock.shift; - } while (unlikely(read_seqcount_retry(>od->seq, seq))); - - ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns); - ts->tv_nsec = ns; - - return mode; -} - static bool kvm_snapshot_has_tsc(struct system_time_snapshot *snap, u64 *tsc_timestamp) { @@ -1523,11 +1447,14 @@ bool kvm_get_monotonic_and_clockread(s64 *kernel_ns, u64 *tsc_timestamp) static bool kvm_get_walltime_and_clockread(struct timespec64 *ts, u64 *tsc_timestamp) { - /* checked again under seqlock below */ - if (!gtod_is_based_on_tsc(pvclock_gtod_data.clock.vclock_mode)) + struct system_time_snapshot snap = {}; + + ktime_get_snapshot_id(CLOCK_REALTIME, &snap); + if (!kvm_snapshot_has_tsc(&snap, tsc_timestamp)) return false; - return gtod_is_based_on_tsc(do_realtime(ts, tsc_timestamp)); + *ts = ktime_to_timespec64(snap.systime); + return true; } #endif -- 2.55.0.679.g6767b8d81c-goog