From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B725AC4338F for ; Mon, 23 Aug 2021 20:56:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 947B8611EF for ; Mon, 23 Aug 2021 20:56:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232548AbhHWU52 (ORCPT ); Mon, 23 Aug 2021 16:57:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232237AbhHWU50 (ORCPT ); Mon, 23 Aug 2021 16:57:26 -0400 Received: from mail-lf1-x131.google.com (mail-lf1-x131.google.com [IPv6:2a00:1450:4864:20::131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 12FE4C061575 for ; Mon, 23 Aug 2021 13:56:43 -0700 (PDT) Received: by mail-lf1-x131.google.com with SMTP id k5so40633199lfu.4 for ; Mon, 23 Aug 2021 13:56:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=MfPwGm7EjtmSmvRvog46PefSQxr+x+Md7zVpSE6q5iY=; b=F2VT7MfdNQfF2aC+mrjNV+Daso+Yq3Z14ZV+Z6h8uaopYNj0tHQL/DCg520+YFSpkz HMHC2ObB8T9d6VnhiY6VgvFdgh5rlX4vqTZi96FDXT1DF/Vwkw+F3Jjn+pn8OWQPMWkB mYCV0IwCPhknXBSAj7wi+114bTreZL51D42va1MYcCoXCWvrXScI0UQLqnLnFLvUkHA0 bBSxLSelk4cilUeMgdUnelmsbIaqk5mZOBrMeTaM+8unId+sJlOGteHTlUeZRNAMFn5z bRzAC4Jjv0D2b83ZDGDLlPorCzx8OR+UxWNK66lljAtyFbDduaVa4Bu6ME55eIQ7e3X5 EAlg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=MfPwGm7EjtmSmvRvog46PefSQxr+x+Md7zVpSE6q5iY=; b=hmHLwunqdlch8KQCej2PaH13J/+OO7jwWFzWMl9w7gILBy4TnLySQNdZFa/m/zE5ZK YTWS/y/OFKbWDeWPxISrTar/BNkjwUO3/HNmsSs0SLxqq8WYsRLrZcaEgXJFEbn9SvBS GMgFqQQDFGfpUA/vBevqZjXtAs6yGUEvpKG+c61dVcGr7CfxSjhmVjRQBegu+3YXkMaJ jeu07Ic+kXaH3eJyEwieEKkrnS1VnQinBx9p3bP3wJjWgI1kSDjYK5KDqa9+7waUN17K OKaZJ7nbzc/C/ISznH+eMXzuBDAJPnfiM2AxtlS8eXzUBANnXZZ6OV80gOup9h3LwYUB dkGg== X-Gm-Message-State: AOAM530pldRPLCQEAZunnBOO/cwqakQjKdHe3p8skUe3Rq9z2qJ3QI+Z 49pLZGndPJO/Bu3DzZ9fhxBvDlhYyteY4bZcJi6wbWYkbVqSew== X-Google-Smtp-Source: ABdhPJw8SHvShGUZj5r3Nx+hzSSyezPNL0Amodo1oDiTqLZh0M2RrBLha351nIEgZs2TuC0YuCzhvO/JGjr8cgLzSXg= X-Received: by 2002:a05:6512:3ba4:: with SMTP id g36mr26490576lfv.80.1629752200949; Mon, 23 Aug 2021 13:56:40 -0700 (PDT) MIME-Version: 1.0 References: <20210816001130.3059564-1-oupton@google.com> <20210816001130.3059564-7-oupton@google.com> In-Reply-To: <20210816001130.3059564-7-oupton@google.com> From: Oliver Upton Date: Mon, 23 Aug 2021 13:56:30 -0700 Message-ID: Subject: Re: [PATCH v7 6/6] KVM: x86: Expose TSC offset controls to userspace To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Cc: Paolo Bonzini , Sean Christopherson , Marc Zyngier , Peter Shier , Jim Mattson , David Matlack , Ricardo Koller , Jing Zhang , Raghavendra Rao Anata , James Morse , Alexandru Elisei , Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, Andrew Jones , Will Deacon , Catalin Marinas Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Paolo, On Sun, Aug 15, 2021 at 5:11 PM Oliver Upton wrote: > > To date, VMM-directed TSC synchronization and migration has been a bit > messy. KVM has some baked-in heuristics around TSC writes to infer if > the VMM is attempting to synchronize. This is problematic, as it depends > on host userspace writing to the guest's TSC within 1 second of the last > write. > > A much cleaner approach to configuring the guest's views of the TSC is to > simply migrate the TSC offset for every vCPU. Offsets are idempotent, > and thus not subject to change depending on when the VMM actually > reads/writes values from/to KVM. The VMM can then read the TSC once with > KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when > the guest is paused. > > Cc: David Matlack > Cc: Sean Christopherson > Signed-off-by: Oliver Upton Could you please squash the following into this patch? We need to advertise KVM_CAP_VCPU_ATTRIBUTES to userspace. Otherwise, happy to resend. Thanks, Oliver arch/x86/kvm/x86.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b946430faaae..b5be1ca07704 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4070,6 +4070,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_VM_COPY_ENC_CONTEXT_FROM: case KVM_CAP_SREGS2: case KVM_CAP_EXIT_ON_EMULATION_FAILURE: + case KVM_CAP_VCPU_ATTRIBUTES: r = 1; break; case KVM_CAP_EXIT_HYPERCALL: -- 2.33.0.rc2.250.ged5fa647cd-goog