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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9476DCD98F5 for ; Wed, 11 Oct 2023 07:28:00 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=sM6P/GYL; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4S549q0WCrz3vXJ for ; Wed, 11 Oct 2023 18:27:59 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=sM6P/GYL; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linuxfoundation.org (client-ip=139.178.84.217; helo=dfw.source.kernel.org; envelope-from=gregkh@linuxfoundation.org; receiver=lists.ozlabs.org) Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4S548r40Dtz300f for ; Wed, 11 Oct 2023 18:27:08 +1100 (AEDT) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id E195661811; Wed, 11 Oct 2023 07:27:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03683C433C7; Wed, 11 Oct 2023 07:27:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1697009225; bh=wdBRBWPG1q+slhhNVCbJyKyr4zxhG5iWNoRBaC45st0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sM6P/GYLthcfQbXg4JirQV4bK0QZKxkEghoQcQYgs8kX/K4EDu95Wcn6L8UQnSDWW rZf7pdAcvMFZONtoU2fTHSUZHnC60MjoaJkIYNcuGZQyH3EmdflPgP4Jl75eTej5di KYtj+i110e2I/lBBebrafdiPPzsNzo4mviAIPdOE= Date: Wed, 11 Oct 2023 09:27:02 +0200 From: Greg Kroah-Hartman To: Anup Patel Subject: Re: [PATCH 2/6] RISC-V: KVM: Change the SBI specification version to v2.0 Message-ID: <2023101107-endorse-large-ef50@gregkh> References: <20231010170503.657189-1-apatel@ventanamicro.com> <20231010170503.657189-3-apatel@ventanamicro.com> <2023101013-overfeed-online-7f69@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-serial@vger.kernel.org, kvm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Atish Patra , linux-kernel@vger.kernel.org, Conor Dooley , Palmer Dabbelt , kvm-riscv@lists.infradead.org, Paul Walmsley , Paolo Bonzini , linux-riscv@lists.infradead.org, Jiri Slaby , Andrew Jones Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Oct 11, 2023 at 11:49:14AM +0530, Anup Patel wrote: > On Tue, Oct 10, 2023 at 10:43 PM Greg Kroah-Hartman > wrote: > > > > On Tue, Oct 10, 2023 at 10:34:59PM +0530, Anup Patel wrote: > > > We will be implementing SBI DBCN extension for KVM RISC-V so let > > > us change the KVM RISC-V SBI specification version to v2.0. > > > > > > Signed-off-by: Anup Patel > > > --- > > > arch/riscv/include/asm/kvm_vcpu_sbi.h | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h > > > index cdcf0ff07be7..8d6d4dce8a5e 100644 > > > --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h > > > +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h > > > @@ -11,7 +11,7 @@ > > > > > > #define KVM_SBI_IMPID 3 > > > > > > -#define KVM_SBI_VERSION_MAJOR 1 > > > +#define KVM_SBI_VERSION_MAJOR 2 > > > > What does this number mean? Who checks it? Why do you have to keep > > incrementing it? > > This number is the SBI specification version implemented by KVM RISC-V > for the Guest kernel. > > The original sbi_console_putchar() and sbi_console_getchar() are legacy > functions (aka SBI v0.1) which were introduced a few years back along > with the Linux RISC-V port. > > The latest SBI v2.0 specification (which is now frozen) introduces a new > SBI debug console extension which replaces legacy sbi_console_putchar() > and sbi_console_getchar() functions with better alternatives. > (Refer, https://github.com/riscv-non-isa/riscv-sbi-doc/releases/download/commit-fe4562532a9cc57e5743b6466946c5e5c98c73ca/riscv-sbi.pdf) > > This series adds SBI debug console implementation in KVM RISC-V > so the SBI specification version advertised by KVM RISC-V must also be > upgraded to v2.0. > > Regarding who checks its, the SBI client drivers in the Linux kernel > will check SBI specification version implemented by higher privilege > mode (M-mode firmware or HS-mode hypervisor) before probing > the SBI extension. For example, the HVC SBI driver (PATCH5) > will ensure SBI spec version to be at least v2.0 before probing > SBI debug console extension. Is this api backwards compatible, or did you just break existing userspace that only expects version 1.0? thanks, greg k-h