From patchwork Wed Jul 20 15:25:57 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 9239807 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 0859560574 for ; Wed, 20 Jul 2016 15:28:29 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EDB5D205B0 for ; Wed, 20 Jul 2016 15:28:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E24B027C26; Wed, 20 Jul 2016 15:28:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 86C7B26246 for ; Wed, 20 Jul 2016 15:28:28 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bPtO1-0001z9-7x; Wed, 20 Jul 2016 15:26:13 +0000 Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bPtNz-0001wa-KL for xen-devel@lists.xen.org; Wed, 20 Jul 2016 15:26:11 +0000 Received: from [85.158.139.211] by server-12.bemta-5.messagelabs.com id 44/4B-01026-2189F875; Wed, 20 Jul 2016 15:26:10 +0000 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrOLMWRWlGSWpSXmKPExsVysyfVTVdoRn+ 4waW/fBZLPi5mcWD0OLr7N1MAYxRrZl5SfkUCa8aqD2dYC95JVWx8+pexgXG5aBcjF4eQwCZG iW3XpzBDOKcZJX7M6mPqYuTkYBPQlLjz+ROYLSIgLXHt82VGEJtZwEHizcd7LCC2sIC7xMR/j 8BqWARUJaZ8mcoKYvMKuEjsP30WLC4hICdx8thksDingKvEtg2PmEFsIaCa1unbmScwci9gZF jFqFGcWlSWWqRrZKqXVJSZnlGSm5iZo2toYKqXm1pcnJiempOYVKyXnJ+7iRHo4XoGBsYdjLv a/Q4xSnIwKYnyqor2hgvxJeWnVGYkFmfEF5XmpBYfYpTh4FCS4LWY3h8uJFiUmp5akZaZAww1 mLQEB4+SCO/HaUBp3uKCxNzizHSI1ClGRSlx3vcgCQGQREZpHlwbLLwvMcpKCfMyMjAwCPEUp BblZpagyr9iFOdgVBLm/QYyhSczrwRu+iugxUxAi+cIgC0uSURISTUw6jz4LH+u+M9+D6dXj5 crrNkUt0et8U1DTGXH6op6n2P7z/+78sSfU7NzdqzHB/m6LJnc+Tt5zduSQnbN3/W5r+H6e+H qgqCLpT3Hynb2cnQtYn/++sFRD0ZRwce7XnqLHarpXFOfslXzm7jn2wteTxm+vv0ftPZU5SkW rociUhzHONl+iTeEKrEUZyQaajEXFScCAGHBl0NqAgAA X-Env-Sender: julien.grall@arm.com X-Msg-Ref: server-2.tower-206.messagelabs.com!1469028368!34565216!2 X-Originating-IP: [217.140.101.70] X-SpamReason: No, hits=0.0 required=7.0 tests= X-StarScan-Received: X-StarScan-Version: 8.77; banners=-,-,- X-VirusChecked: Checked Received: (qmail 21802 invoked from network); 20 Jul 2016 15:26:09 -0000 Received: from foss.arm.com (HELO foss.arm.com) (217.140.101.70) by server-2.tower-206.messagelabs.com with SMTP; 20 Jul 2016 15:26:09 -0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0C2FD3A1; Wed, 20 Jul 2016 08:27:20 -0700 (PDT) Received: from e108454-lin.cambridge.arm.com (e108454-lin.cambridge.arm.com [10.1.218.32]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D29043F387; Wed, 20 Jul 2016 08:26:08 -0700 (PDT) From: Julien Grall To: xen-devel@lists.xen.org Date: Wed, 20 Jul 2016 16:25:57 +0100 Message-Id: <1469028360-20907-5-git-send-email-julien.grall@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1469028360-20907-1-git-send-email-julien.grall@arm.com> References: <1469028360-20907-1-git-send-email-julien.grall@arm.com> Cc: Julien Grall , sstabellini@kernel.org Subject: [Xen-devel] [PATCH v5 4/7] xen/arm: Document the errata implemented in Xen X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" X-Virus-Scanned: ClamAV using ClamSMTP The new document will help to keep track of each erratum Xen is able to handle. The text is based on the Linux doc in Documents/arm64/silicon-errata.txt. Also list the current errata that Xen is aware of. Signed-off-by: Julien Grall Acked-by: Stefano Stabellini Reviewed-by: Konrad Rzeszutek Wilk --- Changes in v4: - Fix grammar in the document : s/by ARM64/on ARM64/ - Add Stefano's acked-by Changes in v3: - Fix grammar in the commit message - s/Linux/Xen/ - Mention that runtime patching is only supported by ARM64 --- docs/misc/arm/silicon-errata.txt | 45 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 docs/misc/arm/silicon-errata.txt diff --git a/docs/misc/arm/silicon-errata.txt b/docs/misc/arm/silicon-errata.txt new file mode 100644 index 0000000..5d54694 --- /dev/null +++ b/docs/misc/arm/silicon-errata.txt @@ -0,0 +1,45 @@ + Silicon Errata and Software Workarounds + ======================================= + +It is an unfortunate fact of life that hardware is often produced with +so-called "errata", which can cause it to deviate from the architecture +under specific circumstances. For hardware produced by ARM, these +errata are broadly classified into the following categories: + + Category A: A critical error without a viable workaround. + Category B: A significant or critical error with an acceptable + workaround. + Category C: A minor error that is not expected to occur under normal + operation. + +For more information, consult one of the "Software Developers Errata +Notice" documents available on infocenter.arm.com (registration +required). + +As far as Xen is concerned, Category B errata may require some special +treatment in the hypervisor. For example, avoiding a particular sequence +of code, or configuring the processor in a particular way. A less common +situation may require similar actions in order to declassify a Category A +erratum into a Category C erratum. These are collectively known as +"software workarounds" and are only required in the minority of cases +(e.g. those cases that both require a non-secure workaround *and* can +be triggered by Xen). + +For software workarounds that may adversely impact systems unaffected by +the erratum in question, a Kconfig entry is added under "ARM errata +workarounds via the alternatives framework". These are enabled by default +and patched in at runtime when an affected CPU is detected. Note that +runtime patching is only supported on ARM64. For less-intrusive workarounds, +a Kconfig option is not available and the code is structured (preferably +with a comment) in such a way that the erratum will not be hit. + +This approach can make it slightly onerous to determine exactly which +errata are worked around in an arbitrary hypervisor source tree, so this +file acts as a registry of software workarounds in the Xen hypervisor and +will be updated when new workarounds are committed and backported to +stable hypervisors. + +| Implementor | Component | Erratum ID | Kconfig | ++----------------+-----------------+-----------------+-------------------------+ +| ARM | Cortex-A15 | #766422 | N/A | +| ARM | Cortex-A57 | #852523 | N/A |