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Fri, 19 Nov 2021 02:21:44 -0800 (PST) Received: from vian.redhat.com ([2a0c:5a80:3c10:3400:3c70:6643:6e71:7eae]) by smtp.gmail.com with ESMTPSA id k27sm14336026wms.41.2021.11.19.02.21.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Nov 2021 02:21:43 -0800 (PST) From: Nicolas Saenz Julienne To: linux-arm-kernel@lists.infradead.org, maz@kernel.org, rostedt@goodmis.org Cc: james.morse@arm.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, nsaenzju@redhat.com, linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu, mingo@redhat.com, mtosatti@redhat.com, nilal@redhat.com Subject: [RFC PATCH 1/2] arm64/tracing: add cntvct based trace clock Date: Fri, 19 Nov 2021 11:21:17 +0100 Message-Id: <20211119102117.22304-2-nsaenzju@redhat.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211119102117.22304-1-nsaenzju@redhat.com> References: <20211119102117.22304-1-nsaenzju@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=nsaenzju@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211119_022149_920589_D8718647 X-CRM114-Status: GOOD ( 16.50 ) 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 Add a new arm64-specific trace clock using the cntvct register, similar to x64-tsc. This gives us: - A clock that is relatively fast (1GHz on armv8.6, 1-50MHz otherwise), monotonic, and resilient to low power modes. - It can be used to correlate events across cpus as well as across hypervisor and guests. By using arch_timer_read_counter() we make sure that armv8.6 cpus use the less expensive CNTVCTSS_EL0, which cannot be accessed speculatively. Signed-off-by: Nicolas Saenz Julienne --- arch/arm64/include/asm/trace_clock.h | 12 ++++++++++++ arch/arm64/kernel/Makefile | 2 +- arch/arm64/kernel/trace_clock.c | 12 ++++++++++++ 3 files changed, 25 insertions(+), 1 deletion(-) create mode 100644 arch/arm64/include/asm/trace_clock.h create mode 100644 arch/arm64/kernel/trace_clock.c diff --git a/arch/arm64/include/asm/trace_clock.h b/arch/arm64/include/asm/trace_clock.h new file mode 100644 index 000000000000..ce4a66d63108 --- /dev/null +++ b/arch/arm64/include/asm/trace_clock.h @@ -0,0 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_ARM64_TRACE_CLOCK_H +#define _ASM_ARM64_TRACE_CLOCK_H + +#include + +extern u64 notrace trace_clock_arm64_cntvct(void); + +# define ARCH_TRACE_CLOCKS \ + { trace_clock_arm64_cntvct, "cntvct", .in_ns = 0 }, + +#endif /* _ASM_ARM64_TRACE_CLOCK_H */ diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 88b3e2a21408..ec9180f0ac90 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -29,7 +29,7 @@ obj-y := debug-monitors.o entry.o irq.o fpsimd.o \ cpufeature.o alternative.o cacheinfo.o \ smp.o smp_spin_table.o topology.o smccc-call.o \ syscall.o proton-pack.o idreg-override.o idle.o \ - patching.o + patching.o trace_clock.o targets += efi-entry.o diff --git a/arch/arm64/kernel/trace_clock.c b/arch/arm64/kernel/trace_clock.c new file mode 100644 index 000000000000..fe1315f368cb --- /dev/null +++ b/arch/arm64/kernel/trace_clock.c @@ -0,0 +1,12 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * arm64 trace clocks + */ +#include + +#include + +u64 notrace trace_clock_arm64_cntvct(void) +{ + return arch_timer_read_counter(); +}