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Thu, 24 Nov 2022 01:30:25 -0800 (PST) Date: Thu, 24 Nov 2022 10:30:21 +0100 From: Samuel Ortiz To: "Hongren (Zenithal) Zheng" Cc: Palmer Dabbelt , Paul Walmsley , Albert Ou , Atish Patra , Anup Patel , Eric Biederman , Kees Cook , linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Michael Kerrisk , linux-man@vger.kernel.org, Jiatai He , Heiko Stuebner , Conor.Dooley@microchip.com Subject: Re: [PATCH v3 2/3] RISC-V: uapi: add HWCAP for Bitmanip/Scalar Crypto Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1669282227; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=CcInVSFUNn3V5gEBEwa46hG0c1UErYT5MY3Lep/oon4=; 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dmarc=none X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 5eao9b4n4q133dwbrh1kt58c5rj3n6hx X-HE-Tag: 1669282226-987890 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jun 13, 2022 at 02:46:35AM +0800, Hongren (Zenithal) Zheng wrote: > diff --git a/arch/riscv/include/uapi/asm/hwcap.h b/arch/riscv/include/uapi/asm/hwcap.h > index 46dc3f5ee99f..bfed3e5c338c 100644 > --- a/arch/riscv/include/uapi/asm/hwcap.h > +++ b/arch/riscv/include/uapi/asm/hwcap.h > @@ -22,4 +22,26 @@ > #define COMPAT_HWCAP_ISA_D (1 << ('D' - 'A')) > #define COMPAT_HWCAP_ISA_C (1 << ('C' - 'A')) > > +/* > + * HWCAP2 flags - for elf_hwcap2 (in kernel) and AT_HWCAP2 > + * > + * As only 32 bits of elf_hwcap (in kernel) could be used > + * and RISC-V has reserved 26 bits of it, other caps like > + * bitmanip and crypto can not be placed in AT_HWCAP > + */ Have we agreed that multi-letter ISA extensions would use hwcap to be exposed to userspace? With so many potential extensions, we could quickly run out of space on AT_HWCAP2 as well. Cheers, Samuel.