From mboxrd@z Thu Jan 1 00:00:00 1970 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C020C433EF for ; Sun, 17 Oct 2021 12:46:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 497A661266 for ; Sun, 17 Oct 2021 12:46:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343549AbhJQMsy (ORCPT ); Sun, 17 Oct 2021 08:48:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:39096 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229648AbhJQMsr (ORCPT ); Sun, 17 Oct 2021 08:48:47 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5B77860EE3; Sun, 17 Oct 2021 12:46:38 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mc5V6-00HKfO-EW; Sun, 17 Oct 2021 13:42:52 +0100 From: Marc Zyngier To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Daniel Lezcano , Will Deacon Cc: Mark Rutland , Thomas Gleixner , Peter Shier , Raghavendra Rao Ananta , Ricardo Koller , Oliver Upton , Catalin Marinas , Linus Walleij , kernel-team@android.com Subject: [PATCH v4 15/17] arm64: Add CNT{P,V}CTSS_EL0 alternatives to cnt{p,v}ct_el0 Date: Sun, 17 Oct 2021 13:42:23 +0100 Message-Id: <20211017124225.3018098-16-maz@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211017124225.3018098-1-maz@kernel.org> References: <20211017124225.3018098-1-maz@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, daniel.lezcano@linaro.org, will@kernel.org, mark.rutland@arm.com, tglx@linutronix.de, pshier@google.com, rananta@google.com, ricarkol@google.com, oupton@google.com, catalin.marinas@arm.com, linus.walleij@linaro.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org CNTPCTSS_EL0 and CNTVCTSS_EL0 are alternatives to the usual CNTPCT_EL0 and CNTVCT_EL0 that do not require a previous ISB to be synchronised (SS stands for Self-Synchronising). Use the ARM64_HAS_ECV capability to control alternative sequences that switch to these low(er)-cost primitives. Note that the counter access in the VDSO is for now left alone until we decide whether we want to allow this. Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/arch_timer.h | 32 +++++++++++++++++++++-------- arch/arm64/include/asm/sysreg.h | 3 +++ 2 files changed, 27 insertions(+), 8 deletions(-) diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h index 519ac1f7f859..af1fafbe7e1d 100644 --- a/arch/arm64/include/asm/arch_timer.h +++ b/arch/arm64/include/asm/arch_timer.h @@ -64,14 +64,26 @@ DECLARE_PER_CPU(const struct arch_timer_erratum_workaround *, static inline notrace u64 arch_timer_read_cntpct_el0(void) { - isb(); - return read_sysreg(cntpct_el0); + u64 cnt; + + asm volatile(ALTERNATIVE("isb\n mrs %0, cntpct_el0", + "nop\n" __mrs_s("%0", SYS_CNTPCTSS_EL0), + ARM64_HAS_ECV) + : "=r" (cnt)); + + return cnt; } static inline notrace u64 arch_timer_read_cntvct_el0(void) { - isb(); - return read_sysreg(cntvct_el0); + u64 cnt; + + asm volatile(ALTERNATIVE("isb\n mrs %0, cntvct_el0", + "nop\n" __mrs_s("%0", SYS_CNTVCTSS_EL0), + ARM64_HAS_ECV) + : "=r" (cnt)); + + return cnt; } #define arch_timer_reg_read_stable(reg) \ @@ -174,8 +186,10 @@ static __always_inline u64 __arch_counter_get_cntpct(void) { u64 cnt; - isb(); - cnt = read_sysreg(cntpct_el0); + asm volatile(ALTERNATIVE("isb\n mrs %0, cntpct_el0", + "nop\n" __mrs_s("%0", SYS_CNTPCTSS_EL0), + ARM64_HAS_ECV) + : "=r" (cnt)); arch_counter_enforce_ordering(cnt); return cnt; } @@ -193,8 +207,10 @@ static __always_inline u64 __arch_counter_get_cntvct(void) { u64 cnt; - isb(); - cnt = read_sysreg(cntvct_el0); + asm volatile(ALTERNATIVE("isb\n mrs %0, cntvct_el0", + "nop\n" __mrs_s("%0", SYS_CNTVCTSS_EL0), + ARM64_HAS_ECV) + : "=r" (cnt)); arch_counter_enforce_ordering(cnt); return cnt; } diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index b268082d67ed..5ce70c034d37 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -507,6 +507,9 @@ #define SYS_CNTFRQ_EL0 sys_reg(3, 3, 14, 0, 0) +#define SYS_CNTPCTSS_EL0 sys_reg(3, 3, 14, 0, 5) +#define SYS_CNTVCTSS_EL0 sys_reg(3, 3, 14, 0, 6) + #define SYS_CNTP_TVAL_EL0 sys_reg(3, 3, 14, 2, 0) #define SYS_CNTP_CTL_EL0 sys_reg(3, 3, 14, 2, 1) #define SYS_CNTP_CVAL_EL0 sys_reg(3, 3, 14, 2, 2) -- 2.30.2