From patchwork Tue Oct 10 10:31:36 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 13415172 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 B8362CD80A2 for ; Tue, 10 Oct 2023 10:34:36 +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=z+l35UqGhdAnWBskmXxb0BzYgfz7nCWKO9oG+me9HJ4=; b=3TeVrx67L7hFXZ PYO1TCjrwq2IJ/mjmVOAmeZtOWjcO3vFWdGaGabesUfJmiIBMI2dKXFwwUSPtz3VmUyd37guYbUnd sZsMv0UsfMNvcpMhA6W4lGqw2WVG2qFg3GnG55h1eRdryXlMjR6MY09MAiiP+ea5bGAnt0YMWU2sj ODdX/w/hXwO2qe52NizNJBUhdPzOmPy80B/QNIzm1DdpdxpxVKNfAoGqp/JQG+LNbJJnuewB/DNJc yZKKAEBnpLumvALYQATISwYP0exlR8XJaa82JY1pS5fJWPTDTPav4LBOmmkbF97oy6cmkEby9smzB aivYOHiY3KnuAdetANog==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qqA3r-00D3GU-0r; Tue, 10 Oct 2023 10:33:59 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qqA3F-00D2kd-2k 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 DE0721477; Tue, 10 Oct 2023 03:34:01 -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 DCB6F3F762; Tue, 10 Oct 2023 03:33:18 -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 35/38] arm64: Avoid cpus_have_const_cap() for ARM64_WORKAROUND_CAVIUM_23154 Date: Tue, 10 Oct 2023 11:31:36 +0100 Message-Id: <20231010103139.3113421-36-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_033322_130399_9A595B33 X-CRM114-Status: GOOD ( 20.01 ) 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 gic_read_iar() we use cpus_have_const_cap() to check for ARM64_WORKAROUND_CAVIUM_23154 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_CAVIUM_23154 cpucap is detected and patched early on the boot CPU before the GICv3 driver is initialized and hence before gic_read_iar() is ever called. Thus it is not necessary to use cpus_have_const_cap(), and alternative_has_cap() is equivalent. In addition, arm64's gic_read_iar() lives in irq-gic-v3.c purely for historical reasons. It was originally added prior to 32-bit arm support in commit: 6d4e11c5e2e8cd54 ("irqchip/gicv3: Workaround for Cavium ThunderX erratum 23154") When support for 32-bit arm was added, 32-bit arm's gic_read_iar() implementation was placed in , but the arm64 version was kept within irq-gic-v3.c as it depended on a static key local to irq-gic-v3.c and it was easier to add ifdeffery, which is what we did in commit: 7936e914f7b0827c ("irqchip/gic-v3: Refactor the arm64 specific parts") Subsequently the static key was replaced with a cpucap in commit: a4023f682739439b ("arm64: Add hypervisor safe helper for checking constant capabilities") Since that commit there has been no need to keep arm64's gic_read_iar() in irq-gic-v3.c. 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. For consistency, move the arm64-specific gic_read_iar() implementation over to arm64's . The ARM64_WORKAROUND_CAVIUM_23154 cpucap is added to cpucap_is_possible() so that code can be elided entirely when this is not possible. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Marc Zyngier Cc: Suzuki K Poulose Cc: Will Deacon --- arch/arm64/include/asm/arch_gicv3.h | 8 ++++++++ arch/arm64/include/asm/cpucaps.h | 2 ++ drivers/irqchip/irq-gic-v3.c | 11 ----------- 3 files changed, 10 insertions(+), 11 deletions(-) diff --git a/arch/arm64/include/asm/arch_gicv3.h b/arch/arm64/include/asm/arch_gicv3.h index 01281a5336cf8..5f172611654b1 100644 --- a/arch/arm64/include/asm/arch_gicv3.h +++ b/arch/arm64/include/asm/arch_gicv3.h @@ -79,6 +79,14 @@ static inline u64 gic_read_iar_cavium_thunderx(void) return 0x3ff; } +static u64 __maybe_unused gic_read_iar(void) +{ + if (alternative_has_cap_unlikely(ARM64_WORKAROUND_CAVIUM_23154)) + return gic_read_iar_cavium_thunderx(); + else + return gic_read_iar_common(); +} + static inline void gic_write_ctlr(u32 val) { write_sysreg_s(val, SYS_ICC_CTLR_EL1); diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h index c5b67a64613e9..34b6428f08bad 100644 --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -52,6 +52,8 @@ cpucap_is_possible(const unsigned int cap) return IS_ENABLED(CONFIG_ARM64_ERRATUM_2645198); case ARM64_WORKAROUND_2658417: return IS_ENABLED(CONFIG_ARM64_ERRATUM_2658417); + case ARM64_WORKAROUND_CAVIUM_23154: + return IS_ENABLED(CONFIG_CAVIUM_ERRATUM_23154); } return true; diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c index eedfa8e9f0772..6d6c01f8f7b47 100644 --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -270,17 +270,6 @@ static void gic_redist_wait_for_rwp(void) gic_do_wait_for_rwp(gic_data_rdist_rd_base(), GICR_CTLR_RWP); } -#ifdef CONFIG_ARM64 - -static u64 __maybe_unused gic_read_iar(void) -{ - if (cpus_have_const_cap(ARM64_WORKAROUND_CAVIUM_23154)) - return gic_read_iar_cavium_thunderx(); - else - return gic_read_iar_common(); -} -#endif - static void gic_enable_redist(bool enable) { void __iomem *rbase;