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[192.237.175.120]) by mx.google.com with ESMTPS id d76si8135816iog.202.2016.07.27.09.39.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Jul 2016 09:39:52 -0700 (PDT) Received-SPF: neutral (google.com: 192.237.175.120 is neither permitted nor denied by best guess record for domain of xen-devel-bounces@lists.xen.org) client-ip=192.237.175.120; Authentication-Results: mx.google.com; spf=neutral (google.com: 192.237.175.120 is neither permitted nor denied by best guess record for domain of xen-devel-bounces@lists.xen.org) smtp.mailfrom=xen-devel-bounces@lists.xen.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bSRpk-0001Mu-UP; Wed, 27 Jul 2016 16:37:24 +0000 Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bSRpj-0001LD-R7 for xen-devel@lists.xen.org; Wed, 27 Jul 2016 16:37:23 +0000 Received: from [85.158.137.68] by server-6.bemta-3.messagelabs.com id 1E/25-28813-343E8975; Wed, 27 Jul 2016 16:37:23 +0000 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrOLMWRWlGSWpSXmKPExsVysyfVTdfp8Yx wg9/3xC2WfFzM4sDocXT3b6YAxijWzLyk/IoE1oym1y/YCh5KV8z8+YCpgbFRrIuRi0NIYCOj xN2Gn+wQzmlGibVzvgA5nBxsApoSdz5/YgKxRQSkJa59vswIYjMLREo8mXmDGcQWFnCXWLq6H yzOIqAq8ebEITCbV8BZYvqG6WBzJATkJE4em8wKYnMKuEj8mPSLDcQWAqr5tu8x8wRG7gWMDK sYNYpTi8pSi3SNDPSSijLTM0pyEzNzdA0NjPVyU4uLE9NTcxKTivWS83M3MQI9XM/AwLiDsfm E3yFGSQ4mJVHeRY4zwoX4kvJTKjMSizPii0pzUosPMcpwcChJ8LY/BMoJFqWmp1akZeYAQw0m LcHBoyTCuwIkzVtckJhbnJkOkTrFqCglzlsLkhAASWSU5sG1wcL7EqOslDAvIwMDgxBPQWpRb mYJqvwrRnEORiVh3qUgU3gy80rgpr8CWswEtLg4FmxxSSJCSqqBselAeOpKi/lOnU2FvfOVTn Ut5BSOMSjgYlm7JGq20Mn2R0eVV2xR1Lh4mmVGe0PaIY6gRknPB6f3KfHUvi4p2tzz3DS9b7X 8MW2XpxZrTRONzk6r3XRUcOGiJ3Vbo+zdJWqf9CXqX9r8aYliP9PHoPJnEWtNnsx5uIvxsU+w 3VKd2worV9evUmIpzkg01GIuKk4EAPN4XeZqAgAA X-Env-Sender: julien.grall@arm.com X-Msg-Ref: server-11.tower-31.messagelabs.com!1469637441!26470055!1 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 20028 invoked from network); 27 Jul 2016 16:37:22 -0000 Received: from foss.arm.com (HELO foss.arm.com) (217.140.101.70) by server-11.tower-31.messagelabs.com with SMTP; 27 Jul 2016 16:37:22 -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 C736028; Wed, 27 Jul 2016 09:38:37 -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 A234D3F25F; Wed, 27 Jul 2016 09:37:20 -0700 (PDT) From: Julien Grall To: xen-devel@lists.xen.org Date: Wed, 27 Jul 2016 17:37:08 +0100 Message-Id: <1469637431-1069-5-git-send-email-julien.grall@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1469637431-1069-1-git-send-email-julien.grall@arm.com> References: <1469637431-1069-1-git-send-email-julien.grall@arm.com> Cc: Julien Grall , sstabellini@kernel.org Subject: [Xen-devel] [PATCH v6 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" 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 v6: - Add Konrad's reviewed-by 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 |