From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f197.google.com (mail-pg1-f197.google.com [209.85.215.197]) (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 73F88492516 for ; Wed, 26 Aug 2026 21:33:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787780011; cv=none; b=OPq9on6ZxwTxCOPF52D1KRwOcAnZetDw6oBP7g3DcA21Qy/QoowqXfrVw7kwHhuFRspcFfuBJmrsHFhHIu9q/rs1nf/qhjt4TRtu5Ltvym3PmQJ6WOZSivLiLKen/ZF4qyqz1tjw6vb/ONlVNxL5H+p/uFOjxfWdy9fDwmIbpW4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787780011; c=relaxed/simple; bh=MifOa2XnbtMroctCQ2vPlzSapAFPZbMD1f0LVHEO7X8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Se6Lof+P2KA9V8WnwfomevQH1/U4HWV4qDSwD1PA4z+I+gDTOo9gsb0AYxJblIeZD8RektGjGTmN8TMlnvnj/Zqf17f9Ni2K06InhlkO/wSfbzDJWQJMBNUR1Tfbpy165SJp6ETI5PCXJwLrZKxtz3qKiOiijhBu3SYspoOtwz0= 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=PC2OcvxK; arc=none smtp.client-ip=209.85.215.197 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="PC2OcvxK" Received: by mail-pg1-f197.google.com with SMTP id 41be03b00d2f7-cc1c1cc5206so1510028a12.3 for ; Wed, 26 Aug 2026 14:33:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1787780009; x=1788384809; 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=sIs19yA05E5+D5bvhm1516uSg4N0iBHK8YfCkpxX2Cg=; b=PC2OcvxKts4dmKa4tevER8k3tej1DRYZUs52ZD5uXDkXdQga7mY9QeNZWuPG3f+iUB wY1lf1M2/F/1Z/ii4VYL3MhU7qKEf0ba4PIrZGxr5IEEnJS5s28H6zpSR3KhMCoF57Z5 G/vnAGRxMt2tmr3tk+mHmdiGY8N+DalR76Zng7j+ZPfpqo24qnve/XptvouipFiojr5b llyQcZZuSMsn/J7DiydAyWKH6pMEBo8DdRzyOazKD/XzJOjSfG0gcVrfyM3+Yhf/mHr9 6bv3w6NYKw1GLIGIdkQRkc0Y4iexWVlNNGuNXwIwfNy9L2Sk0+SQOVuAWQLfxreC3pZB DvvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787780009; x=1788384809; 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=sIs19yA05E5+D5bvhm1516uSg4N0iBHK8YfCkpxX2Cg=; b=ezXfMDOzmQ7KW/FvF+nqlh23V22k7j6QKg6xoxAzgT4r7Y6EWUwAlxAQ5ck5UW5K+j hJ8RRlzvf2/XNP5t81FWEwBoWj1ldCBxbVHc7+C2G7uKSudq3rIp6HXvWbVksKqKuAvX YhnJKWutKYZa89rVch1D0cpCyzjpTPIHSFjNf/QoX7+oMZ0VF5EpPgUwka9HD5KscrI8 J3iJAZ+RXYEd8d71wA6HI/svMvmZOUkPjVThP+7+RxY6RxfhskTkG2uKJcnssfgkMndv 0qCGrGcaq3GQjO+bzjcw0C78AYK8tSkLrNyXL7kpRteZ1q48cXemKd5d7IzxQT/yvIv2 bRdA== X-Forwarded-Encrypted: i=1; AHgh+Rpu8d/uIhRJJXTZRoimnOgcGZ4UtGVyU/nPdVRlQN5SsfC8+SdYJE6dhmu6gQSegghcZA66b8ZGfPv+PJ4=@vger.kernel.org X-Gm-Message-State: AFuF++nDYE6RthBc9l4NpuV+Vcv+n4yFTh3D7KRK75NYRVht0EGbR3OE ZVHAa6H+85+EmcroKS6NyAJ+McStVtsbu8ods7Q9PGJ6xO0mNUwBTpJ9djsvPETu/+qnaW1xMiS mYjSuYQ== X-Received: from pghu17.prod.google.com ([2002:a63:ef11:0:b0:c82:a5b0:d9f0]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:e18b:b0:3be:b0b3:3962 with SMTP id adf61e73a8af0-3cf83f36b8amr21369888637.9.1787780008574; Wed, 26 Aug 2026 14:33:28 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 26 Aug 2026 14:33:01 -0700 In-Reply-To: <20260826213303.914988-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260826213303.914988-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.887.g758fc8c411-goog Message-ID: <20260826213303.914988-22-seanjc@google.com> Subject: [PATCH v10 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 0352bd147c40..34eadc75fee4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1383,82 +1383,6 @@ 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) { @@ -1525,11 +1449,14 @@ 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 -- 2.55.0.887.g758fc8c411-goog