From patchwork Tue Oct 10 10:31:34 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 13415167 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 7BB31CD80A0 for ; Tue, 10 Oct 2023 10:34:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ieNzP5sWEs4N4FHzasbbpSBvln2iXUs5D1SUay1ZUP8=; b=bvOO7mtqhRrq37 ZM1cBvH2zBOMO05vnw5J50b/mW6FUrOyC9mUAE9JJ9S4Hg6jSea9uPf6Vx7/L8aFL4426A4Rb0lF4 Q7n+AGEy3OZuy29UZGbATHMVE2w9QmW8YWgoaM71J4Y+Dd2YPoMz+dh7GWXv1LuzEHlCe/ND+UQvy eyYQXhEl+OskwskzQnoglxZajGSQ43OqK0vLTxWBufY4GiKYfcmI3rgTs8z5ufHpA1fBlI1srLkns PN6cirttHcpP2yNGNOnTH0d5rzXxRSIHCYzEE8Emw65KC/njo28/j//a1aj3C09qB9gqBIAQHeqcV JrSHO476np7EMuheHecw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qqA3p-00D3E6-0X; Tue, 10 Oct 2023 10:33:57 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qqA3A-00D2gc-31 for linux-arm-kernel@lists.infradead.org; Tue, 10 Oct 2023 10:33:31 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D47D8106F; Tue, 10 Oct 2023 03:33:56 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D357C3F762; Tue, 10 Oct 2023 03:33:13 -0700 (PDT) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: ardb@kernel.org, bertrand.marquis@arm.com, boris.ostrovsky@oracle.com, broonie@kernel.org, catalin.marinas@arm.com, daniel.lezcano@linaro.org, james.morse@arm.com, jgross@suse.com, kristina.martsenko@arm.com, mark.rutland@arm.com, maz@kernel.org, oliver.upton@linux.dev, pcc@google.com, sstabellini@kernel.org, suzuki.poulose@arm.com, tglx@linutronix.de, vladimir.murzin@arm.com, will@kernel.org Subject: [PATCH v3 33/38] arm64: Avoid cpus_have_const_cap() for ARM64_WORKAROUND_1742098 Date: Tue, 10 Oct 2023 11:31:34 +0100 Message-Id: <20231010103139.3113421-34-mark.rutland@arm.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20231010103139.3113421-1-mark.rutland@arm.com> References: <20231010103139.3113421-1-mark.rutland@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231010_033317_089521_6B90CBC5 X-CRM114-Status: GOOD ( 17.29 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org In elf_hwcap_fixup() we use cpus_have_const_cap() to check for ARM64_WORKAROUND_1742098, but this is not necessary and cpus_have_cap() would be preferable. For historical reasons, cpus_have_const_cap() is more complicated than it needs to be. Before cpucaps are finalized, it will perform a bitmap test of the system_cpucaps bitmap, and once cpucaps are finalized it will use an alternative branch. This used to be necessary to handle some race conditions in the window between cpucap detection and the subsequent patching of alternatives and static branches, where different branches could be out-of-sync with one another (or w.r.t. alternative sequences). Now that we use alternative branches instead of static branches, these are all patched atomically w.r.t. one another, and there are only a handful of cases that need special care in the window between cpucap detection and alternative patching. Due to the above, it would be nice to remove cpus_have_const_cap(), and migrate callers over to alternative_has_cap_*(), cpus_have_final_cap(), or cpus_have_cap() depending on when their requirements. This will remove redundant instructions and improve code generation, and will make it easier to determine how each callsite will behave before, during, and after alternative patching. The ARM64_WORKAROUND_1742098 cpucap is detected and patched before elf_hwcap_fixup() can run, and hence it is not necessary to use cpus_have_const_cap(). We run cpus_have_const_cap() at most twice: once after finalizing system cpucaps, and potentially once more after detecting mismatched CPUs which support AArch32 at EL0. Due to this, it's not necessary to optimize for many calls to elf_hwcap_fixup(), and it's fine to use cpus_have_cap(). This patch replaces the use of cpus_have_const_cap() with cpus_have_cap(), which will only generate the bitmap test and avoid generating an alternative sequence, resulting in slightly simpler annd smaller code being generated. The ARM64_WORKAROUND_1742098 cpucap is added to cpucap_is_possible() so that code can be elided entirely when this is not possible without requiring ifdeffery or IS_ENABLED() checks at each usage. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: James Morse Cc: Suzuki K Poulose Cc: Will Deacon --- arch/arm64/include/asm/cpucaps.h | 2 ++ arch/arm64/kernel/cpufeature.c | 4 +--- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h index 68b0a658e0828..5613d9e813b20 100644 --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -46,6 +46,8 @@ cpucap_is_possible(const unsigned int cap) return IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0); case ARM64_WORKAROUND_843419: return IS_ENABLED(CONFIG_ARM64_ERRATUM_843419); + case ARM64_WORKAROUND_1742098: + return IS_ENABLED(CONFIG_ARM64_ERRATUM_1742098); case ARM64_WORKAROUND_2658417: return IS_ENABLED(CONFIG_ARM64_ERRATUM_2658417); } diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 9ab7e19b71762..a65c6f00deec5 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2221,10 +2221,8 @@ static void user_feature_fixup(void) static void elf_hwcap_fixup(void) { -#ifdef CONFIG_ARM64_ERRATUM_1742098 - if (cpus_have_const_cap(ARM64_WORKAROUND_1742098)) + if (cpus_have_cap(ARM64_WORKAROUND_1742098)) compat_elf_hwcap2 &= ~COMPAT_HWCAP2_AES; -#endif /* ARM64_ERRATUM_1742098 */ } #ifdef CONFIG_KVM