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 X-Spam-Level: X-Spam-Status: No, score=-14.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_ADSP_CUSTOM_MED,DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3613BC4338F for ; Mon, 9 Aug 2021 16:43:43 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id BF36D60F38 for ; Mon, 9 Aug 2021 16:43:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org BF36D60F38 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org 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:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=O0pRr7GSfRirZHlJMfba2ViAIAH5pNShI+M/q/OSO5k=; b=S0npsAPtAtDnGs kP4vBSCtV/MfIPmpi7DeJ0rQC5lXm/y3kgnfMgb4VOOPL07sGzJnIL+tJBNm3R/1gZTLtqJrWWHbT EgL7OgoSC/3R44b7mqzh0MQJ7cYx+sCSoHelrHNnfScJ23tusN/LTibUClbh6OYlGLqR4/ykt4sVZ tDkwKswVQZQSIYuQVntazL8ZFWfvfYJBt1J+IFcQLrASTToQh2jx4wl9QWrSORkIPMPtIbTxTA29x aFHPM4HrLUqjVgVG/0AJ+kl9tHjOaGWVWKqOS4TneiVnyIcK0HPqdUQS7KPi2+sAqldJiGwn/Mor9 lGzxbN/2n2gq+MpiSrnQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mD8Ly-001TkH-GI; Mon, 09 Aug 2021 16:42:18 +0000 Received: from mail-lj1-x22f.google.com ([2a00:1450:4864:20::22f]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mD8Lu-001TjL-2q for linux-arm-kernel@lists.infradead.org; Mon, 09 Aug 2021 16:42:15 +0000 Received: by mail-lj1-x22f.google.com with SMTP id h17so13203025ljh.13 for ; Mon, 09 Aug 2021 09:42:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=a0L46GNwVNhS6BcTRCD6YmQlBFO5AocAQ1zmSjP7eDA=; b=fV2Ots+U75gJK4rdV7Gkw663FHzj9qPLAGBYDML39+05IaDxr6/7muOK4gFdBB93JC 3ZM6hBuTahI/4ALZXLIpTDaXX7Tuag81H63MSCWBlGtDZJyWAmN1nmo5n4ieurMODrTD uHsYVes4qcwgT08AEzqChKw+l4n0F+U85nXrQaFpy+L6dC9K6QJiip+lYUis8MFaPync 4hYkec9a7O1LZEyWmH+IglksHXDf3qlyQRPhNXny4g26VEJIMUffVh6udi97FXbdomon 5iqANcrhCmCURKMYIRing4Hktf/0tI0BYM6NJ5FsqDWl8MGHG6qV0Jzt5iIp80vfOm0L Js0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=a0L46GNwVNhS6BcTRCD6YmQlBFO5AocAQ1zmSjP7eDA=; b=AXVPvrgR5OUS9czQY2xi5HFYvH/ctOITtKffHpONxuuxl4UXGwLdfieXVhLH6PsRtq AcN5B1JYmP2PRguowbMhxM8T2IOmxCg9TdKWBJMZdK7CV67zZHCgqXEJLSQ2/t67QFn0 BOO41PB8GAH+rlA9DXQQrYvJCGB44wW5rrvaVWoEJ99t0VHtYTtxKqOgFsrDJkK5vyL/ w/HQLVf1tA62L7Xj5cuR1oyOi5CSObieEtyo0mjymojcvsFTqccHd9YSQKQR2u68RXan U778q/nDRQYnciRq8G0MAkQfw04B5JenrLOslM0qhNcmeyXgjwwaxlI4F2IV/VI6rVKC Q9TA== X-Gm-Message-State: AOAM5338Byxh/8OtHhDOb/OEIzKkaHSFoGKXqxSwUO7HgSzMLp2+viJ3 QHgFVVk0/aO85e419YYrs3gfyQ9r3e8oparrO6wZTA== X-Google-Smtp-Source: ABdhPJxqZWQhyMCKHHP0SH7t5512vpnJZZqDvwR48RjMKEqV9en67B8DJvEkAOVH4DCQk83co2JFttVHK5ZZj+mhVaI= X-Received: by 2002:a2e:80ca:: with SMTP id r10mr15371387ljg.331.1628527331936; Mon, 09 Aug 2021 09:42:11 -0700 (PDT) MIME-Version: 1.0 References: <20210809152651.2297337-1-maz@kernel.org> <20210809152651.2297337-14-maz@kernel.org> In-Reply-To: <20210809152651.2297337-14-maz@kernel.org> From: Oliver Upton Date: Mon, 9 Aug 2021 09:42:00 -0700 Message-ID: Subject: Re: [PATCH 13/13] arm64: Add CNT{P, V}CTSS_EL0 alternatives to cnt{p, v}ct_el0 To: Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Mark Rutland , Daniel Lezcano , Thomas Gleixner , Peter Shier , Raghavendra Rao Ananta , Ricardo Koller , Will Deacon , Catalin Marinas , Linus Walleij , kernel-team@android.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210809_094214_194471_B6B8B1D6 X-CRM114-Status: GOOD ( 27.74 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Aug 9, 2021 at 8:48 AM Marc Zyngier wrote: > > 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. What remains to be figured out before we add this to the vDSO (and presumably advertise to userspace through some standard convention)? It would be nice to skip the trap handler altogether, unless there's a can of worms lurking that I'm not aware of. -- Thanks, Oliver > For a good measure, wire the cntvct hooks to also handle CNTVCTSS. > > Signed-off-by: Marc Zyngier > --- > arch/arm64/include/asm/arch_timer.h | 30 +++++++++++++++++++++++------ > arch/arm64/include/asm/esr.h | 6 ++++++ > arch/arm64/include/asm/sysreg.h | 3 +++ > arch/arm64/kernel/traps.c | 11 +++++++++++ > 4 files changed, 44 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h > index b2f056db1225..785411a48512 100644 > --- a/arch/arm64/include/asm/arch_timer.h > +++ b/arch/arm64/include/asm/arch_timer.h > @@ -64,12 +64,26 @@ DECLARE_PER_CPU(const struct arch_timer_erratum_workaround *, > > static inline notrace u64 arch_timer_read_cntpct_el0(void) > { > - return read_sysreg(cntpct_el0); > + u64 cnt; > + > + asm volatile(ALTERNATIVE("isb\n mrs %x0, cntpct_el0", > + "nop\n" __mrs_s("%x0", SYS_CNTPCTSS_EL0), > + ARM64_HAS_ECV) > + : "=r" (cnt)); > + > + return cnt; > } > > static inline notrace u64 arch_timer_read_cntvct_el0(void) > { > - return read_sysreg(cntvct_el0); > + u64 cnt; > + > + asm volatile(ALTERNATIVE("isb\n mrs %x0, cntvct_el0", > + "nop\n" __mrs_s("%x0", SYS_CNTVCTSS_EL0), > + ARM64_HAS_ECV) > + : "=r" (cnt)); > + > + return cnt; > } > > #define arch_timer_reg_read_stable(reg) \ > @@ -166,8 +180,10 @@ static __always_inline u64 __arch_counter_get_cntpct(void) > { > u64 cnt; > > - isb(); > - cnt = read_sysreg(cntpct_el0); > + asm volatile(ALTERNATIVE("isb\n mrs %x0, cntpct_el0", > + "nop\n" __mrs_s("%x0", SYS_CNTPCTSS_EL0), > + ARM64_HAS_ECV) > + : "=r" (cnt)); > arch_counter_enforce_ordering(cnt); > return cnt; > } > @@ -186,8 +202,10 @@ static __always_inline u64 __arch_counter_get_cntvct(void) > { > u64 cnt; > > - isb(); > - cnt = read_sysreg(cntvct_el0); > + asm volatile(ALTERNATIVE("isb\n mrs %x0, cntvct_el0", > + "nop\n" __mrs_s("%x0", SYS_CNTVCTSS_EL0), > + ARM64_HAS_ECV) > + : "=r" (cnt)); > arch_counter_enforce_ordering(cnt); > return cnt; > } > diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h > index 29f97eb3dad4..a305ce256090 100644 > --- a/arch/arm64/include/asm/esr.h > +++ b/arch/arm64/include/asm/esr.h > @@ -227,6 +227,9 @@ > #define ESR_ELx_SYS64_ISS_SYS_CNTVCT (ESR_ELx_SYS64_ISS_SYS_VAL(3, 3, 2, 14, 0) | \ > ESR_ELx_SYS64_ISS_DIR_READ) > > +#define ESR_ELx_SYS64_ISS_SYS_CNTVCTSS (ESR_ELx_SYS64_ISS_SYS_VAL(3, 3, 6, 14, 0) | \ > + ESR_ELx_SYS64_ISS_DIR_READ) > + > #define ESR_ELx_SYS64_ISS_SYS_CNTFRQ (ESR_ELx_SYS64_ISS_SYS_VAL(3, 3, 0, 14, 0) | \ > ESR_ELx_SYS64_ISS_DIR_READ) > > @@ -317,6 +320,9 @@ > #define ESR_ELx_CP15_64_ISS_SYS_CNTVCT (ESR_ELx_CP15_64_ISS_SYS_VAL(1, 14) | \ > ESR_ELx_CP15_64_ISS_DIR_READ) > > +#define ESR_ELx_CP15_64_ISS_SYS_CNTVCTSS (ESR_ELx_CP15_64_ISS_SYS_VAL(9, 14) | \ > + ESR_ELx_CP15_64_ISS_DIR_READ) > + > #define ESR_ELx_CP15_32_ISS_SYS_CNTFRQ (ESR_ELx_CP15_32_ISS_SYS_VAL(0, 0, 14, 0) |\ > ESR_ELx_CP15_32_ISS_DIR_READ) > > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > index 7b9c3acba684..897f9c882895 100644 > --- a/arch/arm64/include/asm/sysreg.h > +++ b/arch/arm64/include/asm/sysreg.h > @@ -506,6 +506,9 @@ > > #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) > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c > index b03e383d944a..16710ca55fbb 100644 > --- a/arch/arm64/kernel/traps.c > +++ b/arch/arm64/kernel/traps.c > @@ -653,6 +653,12 @@ static const struct sys64_hook sys64_hooks[] = { > .esr_val = ESR_ELx_SYS64_ISS_SYS_CNTVCT, > .handler = cntvct_read_handler, > }, > + { > + /* Trap read access to CNTVCTSS_EL0 */ > + .esr_mask = ESR_ELx_SYS64_ISS_SYS_OP_MASK, > + .esr_val = ESR_ELx_SYS64_ISS_SYS_CNTVCTSS, > + .handler = cntvct_read_handler, > + }, > { > /* Trap read access to CNTFRQ_EL0 */ > .esr_mask = ESR_ELx_SYS64_ISS_SYS_OP_MASK, > @@ -729,6 +735,11 @@ static const struct sys64_hook cp15_64_hooks[] = { > .esr_val = ESR_ELx_CP15_64_ISS_SYS_CNTVCT, > .handler = compat_cntvct_read_handler, > }, > + { > + .esr_mask = ESR_ELx_CP15_64_ISS_SYS_MASK, > + .esr_val = ESR_ELx_CP15_64_ISS_SYS_CNTVCTSS, > + .handler = compat_cntvct_read_handler, > + }, > {}, > }; > > -- > 2.30.2 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel