From patchwork Tue Oct 10 10:31:35 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 13415170 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 5B4C6CD80A3 for ; Tue, 10 Oct 2023 10:34:30 +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=I93tSMffEQN+UCkxznuKyojxeDXegCaGtxqjQq9TSx4=; b=a0m8sHU5gHgv/A nr/6MeomcROZhgGH1oZk5BJwf1jloAZc+wgTRJv42h86be3Os4MRxEoV5mz2HJh0xK+i/Xn8V3JDu lx/G27kj3qM6QegPhvisSDNpjZpQOJpjmKlBS7XXGPS4UmadYfz3QW5m8yVok323b4ntFFuGczZUD 21j1M6w3iGbt6BdDouzQHVjDzuGfH1Jn872CirqecniIjYpCuL8g7Sc+hzj2V7GDHllZohIHLdkEu pYyiwiDc5w5bC2S6T4W8UEBQjvDzoRktRqs1c4+GAs9qS60BrLeofxZkchKFvP3kSKHfTCoTugWFu 960LuFRZYyTV7uJYiFUg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qqA3p-00D3F8-2w; 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 1qqA3C-00D2Vh-36 for linux-arm-kernel@lists.infradead.org; Tue, 10 Oct 2023 10:33:34 +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 5ED9DC15; Tue, 10 Oct 2023 03:33:59 -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 5DF7B3F762; Tue, 10 Oct 2023 03:33:16 -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 34/38] arm64: Avoid cpus_have_const_cap() for ARM64_WORKAROUND_2645198 Date: Tue, 10 Oct 2023 11:31:35 +0100 Message-Id: <20231010103139.3113421-35-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_033319_137242_F96D7794 X-CRM114-Status: GOOD ( 18.87 ) 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 We use cpus_have_const_cap() to check for ARM64_WORKAROUND_2645198 but this is not necessary and alternative_has_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_2645198 cpucap is detected and patched before any userspace translation table exist, and the workaround is only necessary when manipulating usrspace translation tables which are in use. Thus it is not necessary to use cpus_have_const_cap(), and alternative_has_cap() is equivalent. This patch replaces the use of cpus_have_const_cap() with alternative_has_cap_unlikely(), which will avoid generating code to test the system_cpucaps bitmap and should be better for all subsequent calls at runtime. The ARM64_WORKAROUND_2645198 cpucap is added to cpucap_is_possible() so that code can be elided entirely when this is not possible, and redundant IS_ENABLED() checks are removed. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Suzuki K Poulose Cc: Will Deacon --- arch/arm64/include/asm/cpucaps.h | 2 ++ arch/arm64/mm/hugetlbpage.c | 3 +-- arch/arm64/mm/mmu.c | 3 +-- 3 files changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h index 5613d9e813b20..c5b67a64613e9 100644 --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -48,6 +48,8 @@ cpucap_is_possible(const unsigned int cap) return IS_ENABLED(CONFIG_ARM64_ERRATUM_843419); case ARM64_WORKAROUND_1742098: return IS_ENABLED(CONFIG_ARM64_ERRATUM_1742098); + case ARM64_WORKAROUND_2645198: + return IS_ENABLED(CONFIG_ARM64_ERRATUM_2645198); case ARM64_WORKAROUND_2658417: return IS_ENABLED(CONFIG_ARM64_ERRATUM_2658417); } diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c index 9c52718ea7509..e9fc56e4f98c0 100644 --- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -555,8 +555,7 @@ bool __init arch_hugetlb_valid_size(unsigned long size) pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) { - if (IS_ENABLED(CONFIG_ARM64_ERRATUM_2645198) && - cpus_have_const_cap(ARM64_WORKAROUND_2645198)) { + if (alternative_has_cap_unlikely(ARM64_WORKAROUND_2645198)) { /* * Break-before-make (BBM) is required for all user space mappings * when the permission changes from executable to non-executable diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 47781bec61719..15f6347d23b69 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -1469,8 +1469,7 @@ early_initcall(prevent_bootmem_remove_init); pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) { - if (IS_ENABLED(CONFIG_ARM64_ERRATUM_2645198) && - cpus_have_const_cap(ARM64_WORKAROUND_2645198)) { + if (alternative_has_cap_unlikely(ARM64_WORKAROUND_2645198)) { /* * Break-before-make (BBM) is required for all user space mappings * when the permission changes from executable to non-executable