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([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.gmail.com with ESMTPSA id p22sm1660354edr.4.2021.04.27.00.04.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Apr 2021 00:04:36 -0700 (PDT) Subject: Re: [PATCH v16 00/17] KVM RISC-V Support To: Anup Patel , Palmer Dabbelt Cc: Paul Walmsley , Anup Patel , Albert Ou , Alexander Graf , Atish Patra , Alistair Francis , Damien Le Moal , KVM General , kvm-riscv@lists.infradead.org, linux-riscv , "linux-kernel@vger.kernel.org List" References: <5b988c4e-25e9-f2b9-b08d-35bc37a245e4@sifive.com> From: Paolo Bonzini Message-ID: Date: Tue, 27 Apr 2021 09:04:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 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-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210427_000443_777304_A7ACB1B9 X-CRM114-Status: GOOD ( 34.70 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On 27/04/21 08:01, Anup Patel wrote: > Hi Paolo, > > Looks like it will take more time for KVM RISC-V to be merged under arch/riscv. > > Let's go ahead with your suggestion of having KVM RISC-V under drivers/staging > so that development is not blocked. > > I will send-out v18 series which will add KVM RISC-V under the staging > directory. > > Should we target Linux-5.14 ? Yes, 5.14 is reasonable. You'll have to adjust the MMU notifiers for the new API introduced in 5.13. Paolo > Regards, > Anup > > On Tue, Apr 27, 2021 at 11:13 AM Paul Walmsley wrote: >> >> On Fri, 9 Apr 2021, Palmer Dabbelt wrote: >> >>> On Wed, 31 Mar 2021 02:21:58 PDT (-0700), pbonzini@redhat.com wrote: >>> >>>> Palmer, are you okay with merging RISC-V KVM? Or should we place it in >>>> drivers/staging/riscv/kvm? >>> >>> I'm certainly ready to drop my objections to merging the code based on >>> it targeting a draft extension, but at a bare minimum I want to get a >>> new policy in place that everyone can agree to for merging code. I've >>> tried to draft up a new policy a handful of times this week, but I'm not >>> really quite sure how to go about this: ultimately trying to build >>> stable interfaces around an unstable ISA is just a losing battle. I've >>> got a bunch of stuff going on right now, but I'll try to find some time >>> to actually sit down and finish one. >>> >>> I know it might seem odd to complain about how slowly things are going >>> and then throw up another roadblock, but I really do think this is a >>> very important thing to get right. I'm just not sure how we're going to >>> get anywhere with RISC-V without someone providing stability, so I want >>> to make sure that whatever we do here can be done reliably. If we don't >>> I'm worried the vendors are just going to go off and do their own >>> software stacks, which will make getting everyone back on the same page >>> very difficult. >> >> I sympathize with Paolo, Anup, and others also. Especially Anup, who has >> been updating and carrying the hypervisor patches for a long time now. >> And also Greentime, who has been carrying the V extension patches. The >> RISC-V hypervisor specification, like several other RISC-V draft >> specifications, is taking longer to transition to the officially "frozen" >> stage than almost anyone in the RISC-V community would like. >> >> Since we share this frustration, the next questions are: >> >> - What are the root causes of the problem? >> >> - What's the right forum to address the root causes? >> >> To me, the root causes of the problems described in this thread aren't >> with the arch/riscv kernel maintenance guidelines, but rather with the >> RISC-V specification process itself. And the right forum to address >> issues with the RISC-V specification process is with RISC-V International >> itself: the mailing lists, the participants, and the board of directors. >> Part of the challenge -- not simply with RISC-V, but with the Linux kernel >> or any other community -- is to ensure that incentives (and disincentives) >> are aligned with the appropriately responsible parts of the community. >> And when it comes to specification development, the right focus to align >> those incentives and disincentives is on RISC-V International. >> >> The arch/riscv patch acceptance guidelines are simply intended to ensure >> that the definition of what is and isn't RISC-V remains clear and >> unambiguous. Even though the guidelines can result in short-term pain, >> the intention is to promote long-term stability and sustainable >> maintainability - particularly since the specifications get baked into >> hardware. We've observed that attempting to chase draft specifications >> can cause significant churn: for example, the history of the RISC-V vector >> specification illustrates how a draft extension can undergo major, >> unexpected revisions throughout its journey towards ratification. One of >> our responsibilities as kernel developers is to minimize that churn - not >> simply for our own sanity, or for the usability of RISC-V, but to ensure >> that we remain members in good standing of the broader kernel community. >> Those of us who were around for the ARM32 and ARM SoC kernel accelerando >> absorbed strong lessons in maintainability, and I doubt anyone here is >> interested in re-learning those the hard way. >> >> RVI states that the association is open to community participation. The >> organizations that have joined RVI, I believe, have a strong stake in the >> health of the RISC-V ecosystem, just as the folks have here in this >> discussion. If the goal really is to get quality specifications out the >> door faster, then let's focus the energy towards building consensus >> towards improving the process at RISC-V International. If that's >> possible, the benefits won't only accrue to Linux developers, but to the >> entire RISC-V hardware and software development community at large. If >> nothing else, it will be an interesting test of whether RISC-V >> International can take action to address these concerns and balance them >> with those of other stakeholders in the process. >> >> >> - Paul > _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv