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([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 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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