From patchwork Sun Aug 6 02:47:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Wang, Xiao W" X-Patchwork-Id: 711050 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 30021EB64DD for ; Sun, 6 Aug 2023 02:39:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229559AbjHFCj0 (ORCPT ); Sat, 5 Aug 2023 22:39:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53068 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229504AbjHFCjZ (ORCPT ); Sat, 5 Aug 2023 22:39:25 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AAAD919AB; Sat, 5 Aug 2023 19:39:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1691289563; x=1722825563; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=tay5dkvntw3AjcFDhiXZE3t/h3WXy5Q2ggqsZ9PrX0o=; b=FEZOzZUR7NtCS95BDzoCgk9hjBYJ/kwDNnqy+tjWhb9BZcXJcxsKAtRo WqJj+8j8jcDK8ptzmXz1qHu/69Onc945nUORSA9Ckwl+LNnwNstnUxlBY 73PTboO9s73zx+/92uJsrSJBap0SWsCMuMmt8wDxXQhGbQu87H255hsR5 PT+ssrqKLVonlPdiTOvjS6zie+DTAlArxiQnfZDf8XZ5IJHMOlY1+8Cem sO1WeO6es9clJ8lvEPU8gUggJEqzfC2SK6Gk7UqclmfmqLIgLmwTQYZ3X cqwwfsNjdYRv0EC2mwdILo0ehVQRHh0L3/PvPhNTuArfnAspsqIG8fS0G g==; X-IronPort-AV: E=McAfee;i="6600,9927,10793"; a="373100369" X-IronPort-AV: E=Sophos;i="6.01,259,1684825200"; d="scan'208";a="373100369" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Aug 2023 19:39:23 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10793"; a="724106192" X-IronPort-AV: E=Sophos;i="6.01,259,1684825200"; d="scan'208";a="724106192" Received: from xiao-desktop.sh.intel.com ([10.239.46.158]) by orsmga007.jf.intel.com with ESMTP; 05 Aug 2023 19:39:20 -0700 From: Xiao Wang To: paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, ardb@kernel.org Cc: anup@brainfault.org, haicheng.li@intel.com, linux-riscv@lists.infradead.org, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, Xiao Wang Subject: [PATCH] RISC-V: Optimize bitops with Zbb extension Date: Sun, 6 Aug 2023 10:47:15 +0800 Message-Id: <20230806024715.3061589-1-xiao.w.wang@intel.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org This patch leverages the alternative mechanism to dynamically optimize bitops (including __ffs, __fls, ffs, fls) with Zbb instructions. When Zbb ext is not supported by the runtime CPU, legacy implementation is used. If Zbb is supported, then the optimized variants will be selected via alternative patching. The legacy bitops support is taken from the generic C implementation as fallback. If the parameter is a build-time constant, we leverage compiler builtin to calculate the result directly, this approach is inspired by x86 bitops implementation. EFI stub runs before the kernel, so alternative mechanism should not be used there, this patch introduces a macro EFI_NO_ALTERNATIVE for this purpose. Signed-off-by: Xiao Wang --- arch/riscv/include/asm/bitops.h | 266 +++++++++++++++++++++++++- drivers/firmware/efi/libstub/Makefile | 2 +- 2 files changed, 264 insertions(+), 4 deletions(-) diff --git a/arch/riscv/include/asm/bitops.h b/arch/riscv/include/asm/bitops.h index 3540b690944b..f727f6489cd5 100644 --- a/arch/riscv/include/asm/bitops.h +++ b/arch/riscv/include/asm/bitops.h @@ -15,13 +15,273 @@ #include #include +#if !defined(CONFIG_RISCV_ISA_ZBB) || defined(EFI_NO_ALTERNATIVE) #include -#include -#include #include +#include +#include + +#else +#include +#include + +#if (BITS_PER_LONG == 64) +#define CTZW "ctzw " +#define CLZW "clzw " +#elif (BITS_PER_LONG == 32) +#define CTZW "ctz " +#define CLZW "clz " +#else +#error "Unexpected BITS_PER_LONG" +#endif + +static __always_inline unsigned long variable__ffs(unsigned long word) +{ + int num; + + asm_volatile_goto( + ALTERNATIVE("j %l[legacy]", "nop", 0, RISCV_ISA_EXT_ZBB, 1) + : : : : legacy); + + asm volatile ( + ".option push\n" + ".option arch,+zbb\n" + "ctz %0, %1\n" + ".option pop\n" + : "=r" (word) : "r" (word) :); + + return word; + +legacy: + num = 0; +#if BITS_PER_LONG == 64 + if ((word & 0xffffffff) == 0) { + num += 32; + word >>= 32; + } +#endif + if ((word & 0xffff) == 0) { + num += 16; + word >>= 16; + } + if ((word & 0xff) == 0) { + num += 8; + word >>= 8; + } + if ((word & 0xf) == 0) { + num += 4; + word >>= 4; + } + if ((word & 0x3) == 0) { + num += 2; + word >>= 2; + } + if ((word & 0x1) == 0) + num += 1; + return num; +} + +/** + * __ffs - find first set bit in a long word + * @word: The word to search + * + * Undefined if no set bit exists, so code should check against 0 first. + */ +#define __ffs(word) \ + (__builtin_constant_p(word) ? \ + (unsigned long)__builtin_ctzl(word) : \ + variable__ffs(word)) + +static __always_inline unsigned long variable__fls(unsigned long word) +{ + int num; + + asm_volatile_goto( + ALTERNATIVE("j %l[legacy]", "nop", 0, RISCV_ISA_EXT_ZBB, 1) + : : : : legacy); + + asm volatile ( + ".option push\n" + ".option arch,+zbb\n" + "clz %0, %1\n" + ".option pop\n" + : "=r" (word) : "r" (word) :); + + return BITS_PER_LONG - 1 - word; + +legacy: + num = BITS_PER_LONG - 1; +#if BITS_PER_LONG == 64 + if (!(word & (~0ul << 32))) { + num -= 32; + word <<= 32; + } +#endif + if (!(word & (~0ul << (BITS_PER_LONG-16)))) { + num -= 16; + word <<= 16; + } + if (!(word & (~0ul << (BITS_PER_LONG-8)))) { + num -= 8; + word <<= 8; + } + if (!(word & (~0ul << (BITS_PER_LONG-4)))) { + num -= 4; + word <<= 4; + } + if (!(word & (~0ul << (BITS_PER_LONG-2)))) { + num -= 2; + word <<= 2; + } + if (!(word & (~0ul << (BITS_PER_LONG-1)))) + num -= 1; + return num; +} + +/** + * __fls - find last set bit in a long word + * @word: the word to search + * + * Undefined if no set bit exists, so code should check against 0 first. + */ +#define __fls(word) \ + (__builtin_constant_p(word) ? \ + (unsigned long)(BITS_PER_LONG - 1 - __builtin_clzl(word)) : \ + variable__fls(word)) + +static __always_inline int variable_ffs(int x) +{ + int r; + + asm_volatile_goto( + ALTERNATIVE("j %l[legacy]", "nop", 0, RISCV_ISA_EXT_ZBB, 1) + : : : : legacy); + + asm volatile ( + ".option push\n" + ".option arch,+zbb\n" + "bnez %1, 1f\n" + "li %0, 0\n" + "j 2f\n" + "1:\n" + CTZW "%0, %1\n" + "addi %0, %0, 1\n" + "2:\n" + ".option pop\n" + : "=r" (r) : "r" (x) :); + + return r; + +legacy: + r = 1; + if (!x) + return 0; + if (!(x & 0xffff)) { + x >>= 16; + r += 16; + } + if (!(x & 0xff)) { + x >>= 8; + r += 8; + } + if (!(x & 0xf)) { + x >>= 4; + r += 4; + } + if (!(x & 3)) { + x >>= 2; + r += 2; + } + if (!(x & 1)) { + x >>= 1; + r += 1; + } + return r; +} + +/** + * ffs - find first set bit in a word + * @x: the word to search + * + * This is defined the same way as the libc and compiler builtin ffs routines. + * + * ffs(value) returns 0 if value is 0 or the position of the first set bit if + * value is nonzero. The first (least significant) bit is at position 1. + */ +#define ffs(x) (__builtin_constant_p(x) ? __builtin_ffs(x) : variable_ffs(x)) + +static __always_inline int variable_fls(unsigned int x) +{ + int r; + + asm_volatile_goto( + ALTERNATIVE("j %l[legacy]", "nop", 0, RISCV_ISA_EXT_ZBB, 1) + : : : : legacy); + + asm volatile ( + ".option push\n" + ".option arch,+zbb\n" + "bnez %1, 1f\n" + "li %0, 0\n" + "j 2f\n" + "1:\n" + CLZW "%0, %1\n" + "neg %0, %0\n" + "addi %0, %0, 32\n" + "2:\n" + ".option pop\n" + : "=r" (r) : "r" (x) :); + + return r; + +legacy: + r = 32; + if (!x) + return 0; + if (!(x & 0xffff0000u)) { + x <<= 16; + r -= 16; + } + if (!(x & 0xff000000u)) { + x <<= 8; + r -= 8; + } + if (!(x & 0xf0000000u)) { + x <<= 4; + r -= 4; + } + if (!(x & 0xc0000000u)) { + x <<= 2; + r -= 2; + } + if (!(x & 0x80000000u)) { + x <<= 1; + r -= 1; + } + return r; +} + +/** + * fls - find last set bit in a word + * @x: the word to search + * + * This is defined in a similar way as ffs, but returns the position of the most + * significant set bit. + * + * fls(value) returns 0 if value is 0 or the position of the last set bit if + * value is nonzero. The last (most significant) bit is at position 32. + */ +#define fls(x) \ + (__builtin_constant_p(x) ? \ + (int)(((x) != 0) ? \ + (sizeof(unsigned int) * 8 - __builtin_clz(x)) : 0) : \ + variable_fls(x)) + +#endif + +#include #include #include -#include #include diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index 16d64a34d1e1..b0f8c495c10f 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -28,7 +28,7 @@ cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \ -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \ -DEFI_HAVE_STRCMP -fno-builtin -fpic \ $(call cc-option,-mno-single-pic-base) -cflags-$(CONFIG_RISCV) += -fpic +cflags-$(CONFIG_RISCV) += -fpic -DEFI_NO_ALTERNATIVE cflags-$(CONFIG_LOONGARCH) += -fpie cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt