From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail02.groups.io (mail02.groups.io [66.175.222.108]) by spool.mail.gandi.net (Postfix) with ESMTPS id 40C7E941064 for ; Mon, 8 Jan 2024 04:06:24 +0000 (UTC) DKIM-Signature: a=rsa-sha256; bh=kAoMxbtGPlCRKizGzSeglhfNISKKEw8O1pOozQUI0cQ=; c=relaxed/simple; d=groups.io; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version:In-Reply-To:Precedence:List-Subscribe:List-Help:Sender:List-Id:Mailing-List:Delivered-To:Reply-To:List-Unsubscribe-Post:List-Unsubscribe:Content-Type:Content-Disposition:Content-Transfer-Encoding; s=20140610; t=1704686782; v=1; b=vZVXJkuE4+xW2srNJqzDxHyBMjUcmjqLap8k5mBitzfhjNbIGUK63gVCgdOXTCs/kWG4nvjo wkGM7Wa2CaWj+fHyMjTzWlsffa7RClf79WC6rSFBBO2w4cS0JhgGw5ikfDKMoxUvhWVO6xJDtcq NFHdHgqH7mdUFDB1JgSjNX2g= X-Received: by 127.0.0.2 with SMTP id 9r5GYY7687511xkfQ1GAoFVx; Sun, 07 Jan 2024 20:06:22 -0800 X-Received: from mail-pj1-f41.google.com (mail-pj1-f41.google.com [209.85.216.41]) by mx.groups.io with SMTP id smtpd.web10.32667.1704686782174364465 for ; Sun, 07 Jan 2024 20:06:22 -0800 X-Received: by mail-pj1-f41.google.com with SMTP id 98e67ed59e1d1-28c7e30c83fso641185a91.1 for ; Sun, 07 Jan 2024 20:06:22 -0800 (PST) X-Gm-Message-State: LNIcO236BZPU909tgAT3gIfix7686176AA= X-Google-Smtp-Source: AGHT+IFwdviUmVlZGd05hzNW8O0oj4kmAT4gAT2h0rn/yN6e4n3LNc7ZjiBg3OmsmH3QPZ/qs0GPLQ== X-Received: by 2002:a17:90a:4313:b0:28c:d9e:9ebc with SMTP id q19-20020a17090a431300b0028c0d9e9ebcmr531157pjg.18.1704686781637; Sun, 07 Jan 2024 20:06:21 -0800 (PST) X-Received: from sunil-laptop ([106.51.188.200]) by smtp.gmail.com with ESMTPSA id fu19-20020a17090ad19300b0028c2b52d132sm5135604pjb.13.2024.01.07.20.06.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 07 Jan 2024 20:06:21 -0800 (PST) Date: Mon, 8 Jan 2024 09:36:13 +0530 From: "Sunil V L" To: Pedro Falcato Cc: devel@edk2.groups.io, Andrei Warkentin , Ard Biesheuvel , Gerd Hoffmann , Jiewen Yao , Laszlo Ersek , Rahul Kumar , Ray Ni , Michael D Kinney , Liming Gao , Zhiguang Liu Subject: Re: [edk2-devel] [PATCH 0/4] RISC-V: Add support for Sstc extension Message-ID: References: <20240103135849.127251-1-sunilvl@ventanamicro.com> MIME-Version: 1.0 In-Reply-To: Precedence: Bulk List-Subscribe: List-Help: Sender: devel@edk2.groups.io List-Id: Mailing-List: list devel@edk2.groups.io; contact devel+owner@edk2.groups.io Reply-To: devel@edk2.groups.io,sunilvl@ventanamicro.com List-Unsubscribe-Post: List-Unsubscribe=One-Click List-Unsubscribe: Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit X-GND-Status: LEGIT Authentication-Results: spool.mail.gandi.net; dkim=pass header.d=groups.io header.s=20140610 header.b=vZVXJkuE; dmarc=none; spf=pass (spool.mail.gandi.net: domain of bounce@groups.io designates 66.175.222.108 as permitted sender) smtp.mailfrom=bounce@groups.io Hi Pedro, On Fri, Jan 05, 2024 at 07:10:40PM +0000, Pedro Falcato wrote: > On Wed, Jan 3, 2024 at 1:59 PM Sunil V L wrote: > > > > This series adds the support for RISV-V Sstc extension in EDK2 timer > > nit: RISC-V > > implementation. Sstc extension allows S-mode software to program the > > timer directly without using SBI calls. > > > > Currently, PCD variable is used to detect whether feature is enabled. By > > default the feature is enabled and platforms need to set the PCD to > > disable the feature if Sstc is not supported. > > > > For RiscVVirtQemu, it is disabled by default (until extension discovery > > feature is enabled). > > I'm curious, what do you want Sstc for? Is the performance difference > measurable (if so, please post numbers, and add them to the commit)? > Does it have any other advantages? > Good question. Without Sstc, timer needs to be programmed using SBI call. The number of instructions via SBI call is way more than a simple CSR access. So, when the CPU supports Sstc, there is no point in using SBI call. The issue with SBI call will be worse under KVM since it has to emulate the timer. Supporting Sstc is futuristic. The platforms can decide not to implement SBI TIME interface at all since they have Sstc. In that case, EDK2 needs to have option to support either. Thanks, Sunil -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#113353): https://edk2.groups.io/g/devel/message/113353 Mute This Topic: https://groups.io/mt/103501836/7686176 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [rebecca@openfw.io] -=-=-=-=-=-=-=-=-=-=-=-