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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 96E58C3DA49 for ; Fri, 26 Jul 2024 12:53:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:In-Reply-To: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=yezTynRGclrUQSM6OY+EIuWUKqt9v7YX+5YM6Gwd5wc=; b=MWYBnXNW4vxWW+Es49g/p+PCxM HGYO9eIuj4KCtvO2XxEX/dhnw2BwmBn7YtkMMDsXgnQKgSSRpCyUhE706bjUJZEWRnQneLuyRqMxV MR1cJvIlCYFADUgqdwcAUAcQIXW78tzuHdfsB8X5V1T89x7nF+prb9ygwyJE1/T+nP7dOv8xV7cFl ngAV9DVX0LQMje01khjSgM+wujASfR+NB8ILwT6MzyraocAHS1v2G9kJvLRh3+bzmeFKilFE7/Sdg z4deqf5aDYxVSOwFQkxXfWI0h9Y1CgHOHj5vBeClWuYA2PAmzNVAaEKEBkIHrH+3Dj+2pKP4CGjRS dqICqAVg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sXKRI-00000003vfB-3wTC; Fri, 26 Jul 2024 12:52:52 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sXKQt-00000003vXh-2cS3 for linux-arm-kernel@lists.infradead.org; Fri, 26 Jul 2024 12:52:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1721998346; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=yezTynRGclrUQSM6OY+EIuWUKqt9v7YX+5YM6Gwd5wc=; b=Vq0SQC1Z3zBZaXzYRr5LrIjdoItqkJT0a9bcNDeMFdJ+wxIj5qVy3b0VyV/GXdzKHBE0Cd Umuc+l9oQKi3fBGrhkQO0/xBfL2KfkzqIlwrjkfNFf7JuNa2GKjqeYXfkLgpbRriR/K5hu qcg1IvAHRbWHhrFjMPizxXRay5vu4fo= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-630-0WFPwxvpPgqGX5UaOZo8cQ-1; Fri, 26 Jul 2024 08:52:25 -0400 X-MC-Unique: 0WFPwxvpPgqGX5UaOZo8cQ-1 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-4280507dc5cso14794135e9.2 for ; Fri, 26 Jul 2024 05:52:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1721998344; x=1722603144; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=yezTynRGclrUQSM6OY+EIuWUKqt9v7YX+5YM6Gwd5wc=; b=H0fM3yv4YivmLfUEQGxmylAjrW6T8uiN4+ezh+Ibt2GARSO8GgvLxROvhFRWMzk7EB NjTGPJYQySV2vNGVxHBnewHp0XNzGC27Fxkw6C29E5HnY93prmKTJjUyM2D8LNEsiujH rEzoBovW3kuaNdwAoGvpo6v1tq/LeQpjgEx1cQJ4NVRIOenyBzsAizNICOQMX7GgokkO /vWOeDgzyv3QJ++EcwBau/mr+j53/Dkg4wps80xqV/IjHvaupCShZouj4UhvvLWN61LI s1WbSfsUKZVBwduqM4TVDFcVjkMMa07Cps31kijEUSFWQNYL04+Iv0OPJ13UazE81j6/ V8cA== X-Forwarded-Encrypted: i=1; AJvYcCW9TYuWMECrNAxVlBb+YkZLxJ9reVO2XfwdYxALwBy03tn86tEEQGCDb+Ycys5N9A3rwh4gukv/wvrbhckBi65qbaQq9MwWW62f4wVklrG95hzT648= X-Gm-Message-State: AOJu0YzXC9qUhIyXLw59JEOvZbIzbB7yOew3juupdFRKczUa54TNoU9i 9+PIMsra6xHtGSvEwiDwPvHZxkzea6Y8eVmZuGLRr3TKUWeUx5O85EkVr+3mQ2LFKdmU+3WZSyK 4baCL7ye2WJtCmhQMKL1oZdwTFHHfkiDgkIBU/oDW1NFpOiXWysy6+AeP22JO8stHY/e4ZyYH X-Received: by 2002:a7b:cc13:0:b0:426:6876:83bb with SMTP id 5b1f17b1804b1-42806b94444mr35917565e9.17.1721998343809; Fri, 26 Jul 2024 05:52:23 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEeZtYe8A1GZTEmL+i7voXFimPt8dBDRrCiuydzX4tPFYqbNapaldNesLi/P0+Gt5ylw7JbVQ== X-Received: by 2002:a7b:cc13:0:b0:426:6876:83bb with SMTP id 5b1f17b1804b1-42806b94444mr35916735e9.17.1721998341579; Fri, 26 Jul 2024 05:52:21 -0700 (PDT) Received: from redhat.com ([2a02:14f:1f7:28ce:f21a:7e1e:6a9:f708]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36b36863b45sm5219141f8f.107.2024.07.26.05.52.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jul 2024 05:52:20 -0700 (PDT) Date: Fri, 26 Jul 2024 08:52:16 -0400 From: "Michael S. Tsirkin" To: David Woodhouse Cc: Richard Cochran , Peter Hilber , linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-rtc@vger.kernel.org, "Ridoux, Julien" , virtio-dev@lists.linux.dev, "Luu, Ryan" , "Chashper, David" , "Mohamed Abuelfotoh, Hazem" , "Christopher S . Hall" , Jason Wang , John Stultz , netdev@vger.kernel.org, Stephen Boyd , Thomas Gleixner , Xuan Zhuo , Marc Zyngier , Mark Rutland , Daniel Lezcano , Alessandro Zummo , Alexandre Belloni , qemu-devel , Simon Horman Subject: Re: [PATCH] ptp: Add vDSO-style vmclock support Message-ID: <20240726084836-mutt-send-email-mst@kernel.org> References: <20240725122603-mutt-send-email-mst@kernel.org> <0959390cad71b451dc19e5f9396d3f4fdb8fd46f.camel@infradead.org> <20240725163843-mutt-send-email-mst@kernel.org> <20240725170328-mutt-send-email-mst@kernel.org> <20240725174327-mutt-send-email-mst@kernel.org> <9261e393083bcd151a017a5af3345a1364b3e0f3.camel@infradead.org> <20240726015613-mutt-send-email-mst@kernel.org> <2e427b102d8fd899a9a3db2ec17a628beb24bc01.camel@infradead.org> MIME-Version: 1.0 In-Reply-To: <2e427b102d8fd899a9a3db2ec17a628beb24bc01.camel@infradead.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240726_055227_756140_DD99DE25 X-CRM114-Status: GOOD ( 15.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Jul 26, 2024 at 09:35:51AM +0100, David Woodhouse wrote: > But for this use case, we only need a memory region that the hypervisor > can update. We don't need any of that complexity of gratuitously > interrupting all the vCPUs just to ensure that none of them can be > running userspace while one of them does an update for itself, > potentially translating from one ABI to another. The hypervisor can > just update the user-visible memory in place. Looks like then your userspace is hypervisor specific, and that's a problem because it's a one way street - there is no way for hypervisor to know what does userspace need, so no way for hypervisor to know which information to provide. No real way to fix bugs. -- MST