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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6A986E7F15B for ; Wed, 27 Sep 2023 03:48:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229641AbjI0Dsr (ORCPT ); Tue, 26 Sep 2023 23:48:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52172 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229672AbjI0Dqo (ORCPT ); Tue, 26 Sep 2023 23:46:44 -0400 Received: from mail-pf1-x430.google.com (mail-pf1-x430.google.com [IPv6:2607:f8b0:4864:20::430]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2B4A61F2E for ; Tue, 26 Sep 2023 19:13:29 -0700 (PDT) Received: by mail-pf1-x430.google.com with SMTP id d2e1a72fcca58-691c05bc5aaso8758541b3a.2 for ; Tue, 26 Sep 2023 19:13:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20230601.gappssmtp.com; s=20230601; t=1695780808; x=1696385608; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=ZV6WWLW/um6fjmDxBYmHw3kQW73zJt+fvsBsocXSqds=; b=DC8d5SUKAatSiQdlBhnd5VF3uy902y7PBvuSVQVWE7DHAzwMT2LVJdtRVQKWIMIT2j 53Gp/cgLv3p7Wy7pJK4vGLZMV250o5YFrhnIRvhrk3IbkkDWHR3D/D2kiWdb5m8EvJrM gnrAAvM+y5lROMtXpstp4RevSM1+m2eGiY4M8r9kUUMjrsyGhLGcxTczj1eIPsLuNreu 8AnUspd8OgN9AqkNB/vK7runY7jNlC7xbXjJUOta1iQ4yFBrKlJyB8Ez6bavloQJQj7I RAqd3wPrUpioJiNsIqcOvgE6HxwfLHcI1KIwXQCc5pBJq6uUx0t7/SZerQOCGSM4rrA+ UrEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695780808; x=1696385608; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=ZV6WWLW/um6fjmDxBYmHw3kQW73zJt+fvsBsocXSqds=; b=ext8Iyf2bxnOpWG0lmQy9Zj8kCnHQcKuBqpf93LdbBGP81EZ0vDEDuRHWHRyaymP/s w9tM5UNOk3rLPjWAGkZDKy8wYm1jmpydClNxVw0YdyhQ3O9WidzBPQg9OwkaOU8Akq7e uQ7poRtUt5mBy2vUuk9VZUtrnd+tCUskCAzbvYR6UboHNQ9kSBthz7GD5CfUNIOZ9Y16 Pm3JRpwaqLKhBdbhZeRkiItwsE7okvwEcyWm6uvBxKINnAHpKCy/kuxHOQbW+7GF8Jd/ v6yxowH3fgufjGHtGWR8dbgJBSIyPF376VOYx9YqHwQ2SbomqIf2DKZBMLKlwTEbH+6j SDtA== X-Gm-Message-State: AOJu0YxXTL0d8S6owSjjgVeyweyo5nyAhuYc7Wz72DdW4itjY3hXHzRW xB1lDNz6F5B+7XkNxSkFsNZFiw== X-Google-Smtp-Source: AGHT+IE1uy7Z2/RTHVKKBhrojjBrMYzG+W9qZc3apbDrbDB/vlS2HSZCgLb+7NFBKhVe0YuAu/kyOA== X-Received: by 2002:a05:6a00:cd5:b0:68c:49e4:bd71 with SMTP id b21-20020a056a000cd500b0068c49e4bd71mr709094pfv.34.1695780808529; Tue, 26 Sep 2023 19:13:28 -0700 (PDT) Received: from ghost ([2601:647:5700:6860:6eef:9e73:7774:1855]) by smtp.gmail.com with ESMTPSA id k12-20020aa7820c000000b0068fda1db80bsm10616571pfi.75.2023.09.26.19.13.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Sep 2023 19:13:28 -0700 (PDT) Date: Tue, 26 Sep 2023 19:13:24 -0700 From: Charlie Jenkins To: Anup Patel Cc: Paolo Bonzini , Atish Patra , Palmer Dabbelt , Paul Walmsley , Conor Dooley , Rob Herring , Krzysztof Kozlowski , Shuah Khan , Andrew Jones , Mayuresh Chitale , devicetree@vger.kernel.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v2 2/9] RISC-V: Detect XVentanaCondOps from ISA string Message-ID: References: <20230925133859.1735879-1-apatel@ventanamicro.com> <20230925133859.1735879-3-apatel@ventanamicro.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Sep 26, 2023 at 09:44:38AM +0530, Anup Patel wrote: > On Tue, Sep 26, 2023 at 9:38 AM Anup Patel wrote: > > > > On Mon, Sep 25, 2023 at 11:18 PM Charlie Jenkins wrote: > > > > > > On Mon, Sep 25, 2023 at 07:08:52PM +0530, Anup Patel wrote: > > > > The Veyron-V1 CPU supports custom conditional arithmetic and > > > > conditional-select/move operations referred to as XVentanaCondOps > > > > extension. In fact, QEMU RISC-V also has support for emulating > > > > XVentanaCondOps extension. > > > > > > > > Let us detect XVentanaCondOps extension from ISA string available > > > > through DT or ACPI. > > > > > > > > Signed-off-by: Anup Patel > > > > Reviewed-by: Andrew Jones > > > > --- > > > > arch/riscv/include/asm/hwcap.h | 1 + > > > > arch/riscv/kernel/cpufeature.c | 1 + > > > > 2 files changed, 2 insertions(+) > > > > > > > > diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h > > > > index 0f520f7d058a..b7efe9e2fa89 100644 > > > > --- a/arch/riscv/include/asm/hwcap.h > > > > +++ b/arch/riscv/include/asm/hwcap.h > > > > @@ -59,6 +59,7 @@ > > > > #define RISCV_ISA_EXT_ZIFENCEI 41 > > > > #define RISCV_ISA_EXT_ZIHPM 42 > > > > #define RISCV_ISA_EXT_SMSTATEEN 43 > > > > +#define RISCV_ISA_EXT_XVENTANACONDOPS 44 > > > > > > > > #define RISCV_ISA_EXT_MAX 64 > > > > > > > > diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c > > > > index 3755a8c2a9de..3a31d34fe709 100644 > > > > --- a/arch/riscv/kernel/cpufeature.c > > > > +++ b/arch/riscv/kernel/cpufeature.c > > > > @@ -182,6 +182,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = { > > > > __RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL), > > > > __RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT), > > > > __RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT), > > > > + __RISCV_ISA_EXT_DATA(xventanacondops, RISCV_ISA_EXT_XVENTANACONDOPS), > > > > }; > > > > > > > > const size_t riscv_isa_ext_count = ARRAY_SIZE(riscv_isa_ext); > > > > -- > > > > 2.34.1 > > > > > > > > > > > > _______________________________________________ > > > > linux-riscv mailing list > > > > linux-riscv@lists.infradead.org > > > > http://lists.infradead.org/mailman/listinfo/linux-riscv > > > > > > I worry about storing vendor extensions in this file. Because vendor > > > extensions are not standardized, they can only be expected to have the > > > desired behavior on hardware with the appropriate vendor id. A couple > > > > Assuming that a vendor extension is only available on hardware with > > appropriate vendor id is not correct because: > > 1) vendor A can allow vendor B to implement a custom extension > > defined by vendor B > > Typo correction: "vendor A can allow vendor B to implement a custom > extension defined by vendor A" > > > 2) vendor A and vendor B can jointly develop a RISC-V CPU where > > both vendors integrate their custom extensions. > > > > It is best to identify a vendor extension independently with a > > "X" string to keep it simple > > and scalable. > > > > Along these lines, each T-Head custom extension should have a > > "XThead" name associated with it. > > > > > months ago I sent a patch to address this by handling vector extensions > > > independently for each vendor [1]. I dropped the patch because it > > > relied upon Heiko's T-Head vector extension support that he stopped > > > working on. However, I can revive this patch so you can build off of it. > > > > At least, the conditional operations don't need a hwprobe interface > > because an application is either compiled with or without conditional > > operations. In other words, effective use of conditional operation is > > only possible if compiler generates these instructions based on > > code patterns. > > I was conflating hwprobe with hwcap when I was thinking about this. However, I think it might still be beneficial to split out the vendor extensions. It is possible for vendors to implement each other's extensions but I don't expect that to be the average case. Because I do not expect this to be the average case, riscv_isa_ext becomes needlessly large as it has to contain the extensions of every vendor. > > > > > > This scheme has the added benefit that vendors do not have to worry > > > about conficting extensions, and the kernel does not have to act as a > > > key registry for vendors. > > > > How can vendor extensions conflict if they all follow the > > "X" naming scheme ? > > > > > > > > What are your thoughts? > > > > > > - Charlie > > > > > > [1] https://lore.kernel.org/lkml/20230705-thead_vendor_extensions-v1-2-ad6915349c4d@rivosinc.com/ > > > > > > > Regards, > > Anup > > Regards, > Anup - Charlie