From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0817D70 for ; Fri, 21 May 2021 17:21:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1621617679; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qwR/0GNmU1erDIzfTwdpHCjLZxYNU+OZQVJXmXfAYfM=; b=Rp001alysR6Djrsu1XUaGGxzM6zHSzI8FjdLh8ir4ovfhyPGCDKWWIJGEvvh2Uxq4qEeVT a70//g8HSzlP3PgjU1pqzJppRC1UGMI6AeKGepPzwHSIb3uF3eMPMWR1d/ADWdT4hUgZ2t +VyHIKmjLSFmtDwbo/ll5iF/M/JbOeo= Received: from mail-ej1-f69.google.com (mail-ej1-f69.google.com [209.85.218.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-167-RHHSVQwHM1at1AqFZOs7Yg-1; Fri, 21 May 2021 13:21:17 -0400 X-MC-Unique: RHHSVQwHM1at1AqFZOs7Yg-1 Received: by mail-ej1-f69.google.com with SMTP id bi3-20020a170906a243b02903933c4d9132so6492408ejb.11 for ; Fri, 21 May 2021 10:21:16 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:subject:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=qwR/0GNmU1erDIzfTwdpHCjLZxYNU+OZQVJXmXfAYfM=; b=gGx0+XY7J2ZjBH0s4PfXZoB5p4ZKnrjRTSDrB/zD7WI8E83nt/xH6ix3yUXThweMZ+ 9PUUhGqgnoaHsvJo3rS4Jq38VwiQkVm9DikpiLr0hZIe3svHfu0fZOogPXu7IcdilwCL uCHb2UBqXmFC1Oh4F7KCOEkOpH1UymZT3QsW2J8F2gFCG784pGKN5+X+xAcohURU5SpI Gyj4xZnZnmVCXgHRIttGiS+ogqShTmh+mbngQTn9/bniYT9JcjFFtorglbsGHfMAYM/v 2lVH8wPP2OKaT0Pjt9kfVDBtiC5JUjvzJLUF9Dv+0RJEl6C1QlP2GPvXw7uPoibFRUZ4 cEYQ== X-Gm-Message-State: AOAM533rsqnz8VY162O+b4n31IVds2z1v29rsoLE+rP7N0c/fM/6pJon VfkIvgOQ/NoLlHIHZqvsYun6NTsINmQX4W65J++OAKosoV7a4AueVhgEOwTIQNbnnR83Y9kxsir kgl9ewHnM/HsMDhY57/FvSmzmFGZUsgs5lRW6vjh+j92l37nIDGgx5d1542DFr7Hmab01Lfanow +Rbw== X-Received: by 2002:aa7:cd03:: with SMTP id b3mr12350077edw.206.1621617675196; Fri, 21 May 2021 10:21:15 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxs1PPEtRit2YsbPl3fyEJzFG+BMaVTPI5cJbO+TcDqnJ8UNSbmnYU1JgZsPGIv6fh/e498XA== X-Received: by 2002:aa7:cd03:: with SMTP id b3mr12350048edw.206.1621617675016; Fri, 21 May 2021 10:21:15 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:c8dd:75d4:99ab:290a? ([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id m12sm4079494edc.40.2021.05.21.10.21.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 May 2021 10:21:14 -0700 (PDT) To: Palmer Dabbelt , Greg KH Cc: anup@brainfault.org, Anup Patel , Paul Walmsley , aou@eecs.berkeley.edu, corbet@lwn.net, graf@amazon.com, Atish Patra , Alistair Francis , Damien Le Moal , kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-staging@lists.linux.dev References: From: Paolo Bonzini Subject: Re: [PATCH v18 00/18] KVM RISC-V Support Message-ID: Date: Fri, 21 May 2021 19:21:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit On 21/05/21 19:13, Palmer Dabbelt wrote: >> > > I don't view this code as being in a state where it can be > maintained, at least to the standards we generally set within the > kernel. The ISA extension in question is still subject to change, it > says so right at the top of the H extension > > > {\bf Warning! This draft specification may change before being > accepted as standard by the RISC-V Foundation.} To give a complete picture, the last three relevant changes have been in August 2019, November 2019 and May 2020. It seems pretty frozen to me. In any case, I think it's clear from the experience with Android that the acceptance policy cannot succeed. The only thing that such a policy guarantees, is that vendors will use more out-of-tree code. Keeping a fully-developed feature out-of-tree for years is not how Linux is run. > I'm not sure where exactly the line for real hardware is, but for > something like this it would at least involve some chip that is > widely availiable and needs the H extension to be useful Anup said that "quite a few people have already implemented RISC-V H-extension in hardware as well and KVM RISC-V works on real HW as well". Those people would benefit from having KVM in the Linus tree. Paolo