From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (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 2212570 for ; Fri, 21 May 2021 17:47:54 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 2FA836135C; Fri, 21 May 2021 17:47:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1621619273; bh=xOq3jj2UbZa7lDCzy39FJlunDF10xKfCJ5FyeAWwORQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KBD6lbrTjL2LnMejfzX5ud65busPKGi/lpJ5soBktqKEEpW0q6Q6RPLPSTn5hfIHM +M+fDBS/u7VpUhjC6axyc2792Z/IHzPsQ6ZlEk30RF72T56Ut8cvZkW3OYoikfOVsI An7+UKMeTx7OhM7Vig7bmYyLVyhSJqX/6Jz6i2BU= Date: Fri, 21 May 2021 19:47:51 +0200 From: Greg KH To: Paolo Bonzini Cc: Palmer Dabbelt , 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 Subject: Re: [PATCH v18 00/18] KVM RISC-V Support Message-ID: References: X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, May 21, 2021 at 07:21:12PM +0200, Paolo Bonzini wrote: > 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. Great, but is this really true? If so, what hardware has this? I have a new RISC-V device right here next to me, what would I need to do to see if this is supported in it or not? If this isn't in any hardware that anyone outside of internal-to-company-prototypes, then let's wait until it really is in a device that people can test this code on. What's the rush to get this merged now if no one can use it? thanks, greg k-h