From patchwork Tue May 17 10:07:43 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Clark X-Patchwork-Id: 12852244 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 B7B40C433EF for ; Tue, 17 May 2022 10:10:26 +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=LDbe6EuenvY7TCJIcmQ+T9/cbxM1B8JB8sII1jkIQ2Q=; b=haWfpD+YMnGlf7 cDDoedbrrWCiGLZUpro2XK0jr8UInnrIx/K8Ydp5/vvR/f/I10clONkbAN1cfakU7ARVC5hcSA/tN /c+GSuyxxo4/3as6BamYleLGQvlWaV6zQW1CvC3bOdPTXSGUNAwjJ1SIXbGO6v6aXkp0dqq2yXOfC wOhbF/JS0E/grjPgTHyENi2v7BK//wi1omHXK6lTfqRWAesahYcr467ak+fnl/KBdfglL7DVZO6Pb UBg4esCHXuQCIJ7ssa8vebOD+9rWn2HLfPol1qRNX03dzalSNNPV/KAablU2jeZENwTalHYOJ9lnt YR3avrPiGlxat2pqWRgg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nqu8s-00Cwdy-Ua; Tue, 17 May 2022 10:09:27 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nqu8a-00CwYO-2j for linux-arm-kernel@lists.infradead.org; Tue, 17 May 2022 10:09:09 +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 772A312FC; Tue, 17 May 2022 03:09:06 -0700 (PDT) Received: from e121896.warwick.arm.com (e121896.warwick.arm.com [10.32.33.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 64DA93F66F; Tue, 17 May 2022 03:09:04 -0700 (PDT) From: James Clark To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, broonie@kernel.org, acme@kernel.org Cc: german.gomez@arm.com, leo.yan@linaro.org, mathieu.poirier@linaro.org, john.garry@huawei.com, James Clark , Catalin Marinas , Will Deacon , Jonathan Corbet , Mark Rutland , linux-doc@vger.kernel.org Subject: [PATCH v2 2/2] arm64/sve: Add Perf extensions documentation Date: Tue, 17 May 2022 11:07:43 +0100 Message-Id: <20220517100743.3020667-3-james.clark@arm.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20220517100743.3020667-1-james.clark@arm.com> References: <20220517100743.3020667-1-james.clark@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220517_030908_224195_C03A0D11 X-CRM114-Status: GOOD ( 12.00 ) 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 Document that the VG register is available in Perf samples Signed-off-by: James Clark Reviewed-by: Mark Brown --- Documentation/arm64/sve.rst | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/Documentation/arm64/sve.rst b/Documentation/arm64/sve.rst index 9d9a4de5bc34..b34a1467057f 100644 --- a/Documentation/arm64/sve.rst +++ b/Documentation/arm64/sve.rst @@ -402,6 +402,24 @@ The regset data starts with struct user_sve_header, containing: * Modifying the system default vector length does not affect the vector length of any existing process or thread that does not make an execve() call. +10. Perf extensions +-------------------------------- + +* The arm64 specific DWARF standard [5] added the VG (Vector Granule) register + at index 46. This register is used for DWARF unwinding when variable length + SVE registers are pushed onto the stack. + +* Its value is equivalent to the current SVE vector length (VL) in bits divided + by 64. + +* The value is included in Perf samples in the regs[46] field if + PERF_SAMPLE_REGS_USER is set and the sample_regs_user mask has bit 46 set. + +* The value is the current value at the time the sample was taken, and it can + change over time. + +* If the system doesn't support SVE when perf_event_open is called with these + settings, the event will fail to open. Appendix A. SVE programmer's model (informative) ================================================= @@ -543,3 +561,5 @@ References http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055c/IHI0055C_beta_aapcs64.pdf http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html Procedure Call Standard for the ARM 64-bit Architecture (AArch64) + +[5] https://github.com/ARM-software/abi-aa/blob/main/aadwarf64/aadwarf64.rst