From nobody Fri Feb 13 15:06:39 2026 Received: from mail-pl1-f174.google.com (mail-pl1-f174.google.com [209.85.214.174]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 495138493 for ; Fri, 24 May 2024 18:56:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.174 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716576988; cv=none; b=T+WV2PZY7V6pQzvRPHmeTOiLl7X0EZySA1t5CnEJyMU9KLufjDgFYhJBAueQ2sSsUSDJY2WM1YtuuEkNHRtH/WVgOGktm8ozAcAvxYleJQJDR+LjqAqhp9D2uYR6G1Kob/C74ZNDV7qrL2fEtI8fpXWOW5NbXJJRmG6M7Lgvgwg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716576988; c=relaxed/simple; bh=EnRUwxPjMwARAQhkc9VptC1FFM+vVJDf4lE+8efMjmY=; h=Subject:Date:Message-ID:MIME-Version:Cc:From:To; b=m3wzQp/wTJjQaLJQeOsv39Q+tYM3ymfOEFMlm22nWjjYUkl3qSnYpHwAUWr6ZJMfzsRRGnK5va+9N4U3GhnRFLpshyDs6M+BdAggZhuVORj6bkU6kYGhThgmQyv9NUYmdvqQncdnnynj3fL9DLCfGHpPZ1SMV9B1Tu5Ri3Z91Qg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rivosinc.com; spf=pass smtp.mailfrom=rivosinc.com; dkim=pass (2048-bit key) header.d=rivosinc-com.20230601.gappssmtp.com header.i=@rivosinc-com.20230601.gappssmtp.com header.b=QsmUEuva; arc=none smtp.client-ip=209.85.214.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rivosinc.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rivosinc.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=rivosinc-com.20230601.gappssmtp.com header.i=@rivosinc-com.20230601.gappssmtp.com header.b="QsmUEuva" Received: by mail-pl1-f174.google.com with SMTP id d9443c01a7336-1f44b52f86cso9882035ad.1 for ; Fri, 24 May 2024 11:56:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20230601.gappssmtp.com; s=20230601; t=1716576985; x=1717181785; darn=vger.kernel.org; h=to:from:cc:content-transfer-encoding:mime-version:message-id:date :subject:from:to:cc:subject:date:message-id:reply-to; bh=xLUodbpWlHV/m1Bt2U9fTwJmOlm4ytnN9TrwQjmnMvY=; b=QsmUEuvaApp4KX0juj4+Xy3f7J7Nx/4zsj9O2XA2CakDNg6ofjYhOc1s2dkwJrOwwa yoCZOr1FGiKg4niD//zE7JhhCWu/4l+BM7dp4VMYhtdco/7nPzj6MyiVT5SYCWTOteqE jkU1MuvyGd8EOvsLB/l5fet1aYRwFrwpk66cyQhLdrm+FeSQHsdcSAVNdUxrdQD5bMhr Pg1vKDsbr53SUl8HQsKMEjQ/Clq6DzOnjttyOr6MG3mxJ8eOA8ASlRdlO6jbIbd0oxgA MvEi3xVSj32lqATv5cqvUIwpfXs1Cwn8Y+4hAKQ7bpw/isPJ5GyRfkAojgHE64piNDXw sHQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1716576985; x=1717181785; h=to:from:cc:content-transfer-encoding:mime-version:message-id:date :subject:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=xLUodbpWlHV/m1Bt2U9fTwJmOlm4ytnN9TrwQjmnMvY=; b=qUo3EHwkNJINtSLIgQDtYorH8/ne90nHrpWTdzehdQBcbrzpuQmIha6XD6gp5nfE7Q zWPdaZK9mMoaUy1mzJ4Eqsqhr0JgjjOSdZazyPOJpVS/txzFfTlIFCHS20NsBumH8/Mr 2vnz328/2GMtdSFU4Ufxz9m5co9B+lbVfN4p0Wpu4UOzzbzm0ffeQIjQ4TFxaZt1lh7N wUrPqBoMGdVQQUDupi3qSrk968YnL1kb6QyXeor6wgH5gBqXdvVEz0jNfX9tniQydKun kGqF5DhilHFKQA9xuldlUWO1V9+9SihXVzXTIncJcvb8I95q/8c1T9TRDR+ivUgJ6MjS 6S1g== X-Forwarded-Encrypted: i=1; AJvYcCWocvO4rZugPXsdxi8t86N1o5DbXd2A2YTynesI/jFNBxWGZTLqGTl+baYJ/h3FDr/PEVCoJv6zw0sbT7zUbTkkJvB/h7s5tc442jlk X-Gm-Message-State: AOJu0YyRqw0HzyQ8K40FM0EROWPms3HC14wzTL2t96kPmBN6PLyAms5L nHFhztoK4jwLz4GPXxMYmNxm1AEolVbtajlw2Za7fTZ3pfRthQj0i8bOYmtSYLA= X-Google-Smtp-Source: AGHT+IHmjdtRpnISU8MeUC5uHlVT+aFruq8xOMm5QCnc85cjYN6x/xbnArZ5Bph7B9WPdNdkHZeeug== X-Received: by 2002:a17:902:e746:b0:1e4:3909:47c0 with SMTP id d9443c01a7336-1f4498f0d96mr42599825ad.62.1716576985229; Fri, 24 May 2024 11:56:25 -0700 (PDT) Received: from localhost ([192.184.165.199]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f44c9c7f32sm17084505ad.281.2024.05.24.11.56.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 May 2024 11:56:24 -0700 (PDT) Subject: [PATCH] Documentation: RISC-V: uabi: Only scalar misaligned loads are supported Date: Fri, 24 May 2024 11:56:00 -0700 Message-ID: <20240524185600.5919-1-palmer@rivosinc.com> X-Mailer: git-send-email 2.45.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Cc: corbet@lwn.net, Paul Walmsley , Palmer Dabbelt , aou@eecs.berkeley.edu, costa.shul@redhat.com, Conor Dooley , linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Palmer Dabbelt From: Palmer Dabbelt To: linux-riscv@lists.infradead.org Content-Type: text/plain; charset="utf-8" From: Palmer Dabbelt We're stuck supporting scalar misaligned loads in userspace because they were part of the ISA at the time we froze the uABI. That wasn't the case for vector misaligned accesses, so depending on them unconditionally is a userspace bug. All extant vector hardware traps on these misaligned accesses. Signed-off-by: Palmer Dabbelt Reviewed-by: Conor Dooley --- Documentation/arch/riscv/uabi.rst | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/Documentation/arch/riscv/uabi.rst b/Documentation/arch/riscv/u= abi.rst index 54d199dce78b..2b420bab0527 100644 --- a/Documentation/arch/riscv/uabi.rst +++ b/Documentation/arch/riscv/uabi.rst @@ -65,4 +65,6 @@ the extension, or may have deliberately removed it from t= he listing. Misaligned accesses ------------------- =20 -Misaligned accesses are supported in userspace, but they may perform poorl= y. +Misaligned scalar accesses are supported in userspace, but they may perform +poorly. Misaligned vector accesses are only supported if the Zicclsm exte= nsion +is supported. --=20 2.45.0