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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 E1D9BC32750 for ; Fri, 2 Aug 2019 08:30:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C52C72187F for ; Fri, 2 Aug 2019 08:30:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404188AbfHBIaO (ORCPT ); Fri, 2 Aug 2019 04:30:14 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:37183 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726756AbfHBIaO (ORCPT ); Fri, 2 Aug 2019 04:30:14 -0400 Received: by mail-wr1-f65.google.com with SMTP id n9so51185192wrr.4 for ; Fri, 02 Aug 2019 01:30:12 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=+MjSLRhTHy/z+LM8sRLnyEruabbpzZhCsOii1dxVU9Y=; b=ABjjmBa63ORx5S85nQTU3ArYFnduFCEPXOIcUyf85QtNLRegddmzQe+zhTlWqIEKBw +ssZAR7i1HHBcEa6y8e2/7DZf30iNzpUtzbsYJ4iEvU3cZGIuR36N8E0HDXqawwrUvQT ao785ZMHt4k+7N92p9JsH+eOeZiMKlN5rXciTIueCtcqP8DX5gZvYxeuIof5D5VpB+YO zCGLh4ztQzWeVVlcyy0I0gku7ZnxzRfXFgVPxlY4TxM6ypp49ErrrswShEL0zQDnARGH DniLzsWnkHA8Z0cY0o5prbZNcjEdLUy+dPlMqHCZ4KTTcfOPFPUFXbO41SjgtMUUmWdR 4jJA== X-Gm-Message-State: APjAAAVYWM0W0468+ATF3J2V8qVP/VBKMz+eXQR0ucDRWWS9PjQ8cBPO 0upcWZYR+7LVZ1vLTUgAVM/Usg== X-Google-Smtp-Source: APXvYqxQ8H0EwfjmiYP1/SUacCSArAMVaY+7Hsw2aimu6rkqpcHBrjydXWxpNn5htwW5YM1MsKxGqQ== X-Received: by 2002:adf:dcc6:: with SMTP id x6mr117116586wrm.322.1564734611723; Fri, 02 Aug 2019 01:30:11 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:4013:e920:9388:c3ff? ([2001:b07:6468:f312:4013:e920:9388:c3ff]) by smtp.gmail.com with ESMTPSA id b8sm99851723wmh.46.2019.08.02.01.30.10 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Fri, 02 Aug 2019 01:30:11 -0700 (PDT) Subject: Re: [RFC PATCH v2 08/19] RISC-V: KVM: Implement VCPU world-switch To: Anup Patel , Palmer Dabbelt , Paul Walmsley , Radim K Cc: Daniel Lezcano , Thomas Gleixner , Atish Patra , Alistair Francis , Damien Le Moal , Christoph Hellwig , Anup Patel , "kvm@vger.kernel.org" , "linux-riscv@lists.infradead.org" , "linux-kernel@vger.kernel.org" References: <20190802074620.115029-1-anup.patel@wdc.com> <20190802074620.115029-9-anup.patel@wdc.com> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: <72d8efbf-ec62-ab1e-68bf-e0c5f0bc256e@redhat.com> Date: Fri, 2 Aug 2019 10:30:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190802074620.115029-9-anup.patel@wdc.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 02/08/19 09:47, Anup Patel wrote: > + /* Save Host SSTATUS, HSTATUS, SCRATCH and STVEC */ > + csrr t0, CSR_SSTATUS > + REG_S t0, (KVM_ARCH_HOST_SSTATUS)(a0) > + csrr t1, CSR_HSTATUS > + REG_S t1, (KVM_ARCH_HOST_HSTATUS)(a0) > + csrr t2, CSR_SSCRATCH > + REG_S t2, (KVM_ARCH_HOST_SSCRATCH)(a0) > + csrr t3, CSR_STVEC > + REG_S t3, (KVM_ARCH_HOST_STVEC)(a0) > + A possible optimization: if these cannot change while Linux runs (I am thinking especially of STVEC and HSTATUS, but perhaps SSCRATCH can be saved on kvm_arch_vcpu_load too) you can avoid the csrr and store. Paolo