From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail02.groups.io (mail02.groups.io [66.175.222.108]) by spool.mail.gandi.net (Postfix) with ESMTPS id D815F740041 for ; Tue, 23 Jan 2024 16:59:44 +0000 (UTC) DKIM-Signature: a=rsa-sha256; bh=4qlV+ah4K3UEZMF5lxdhBGYIypucKZ8B2vQKeWnvXbA=; c=relaxed/simple; d=groups.io; h=Message-ID:Date:MIME-Version:User-Agent:Subject:To:Cc:References:From:Autocrypt:In-Reply-To:Feedback-ID:Precedence:List-Subscribe:List-Help:Sender:List-Id:Mailing-List:Delivered-To:Reply-To:List-Unsubscribe-Post:List-Unsubscribe:Content-Language:Content-Type:Content-Transfer-Encoding; s=20140610; t=1706029183; v=1; b=YXjjan07pR0OFO3MHWaaaiFPGbF2HddGWyaAreR+D4uctvGLCPyEvtzDEcOFS5sRhINzjE9t b1pElxRsElFORnah0aqU2B3XmYmxNkrP9TbBLdU95e3huJ4hZpgjJpl1ETIrvyKWepGEyMP9kWu fKK9XZTBtvhfEYTZgQGl0K2c= X-Received: by 127.0.0.2 with SMTP id TZeNYY7687511xIZAbvajwUS; Tue, 23 Jan 2024 08:59:43 -0800 X-Received: from a7-18.smtp-out.eu-west-1.amazonses.com (a7-18.smtp-out.eu-west-1.amazonses.com [54.240.7.18]) by mx.groups.io with SMTP id smtpd.web11.18399.1706029182746530020 for ; Tue, 23 Jan 2024 08:59:43 -0800 Message-ID: <0102018d374367e0-ac396f00-34fb-40ab-8fe6-f68d0458d373-000000@eu-west-1.amazonses.com> Date: Tue, 23 Jan 2024 16:59:40 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [edk2-devel] [PATCH v3 3/5] MdeModulePkg: Do nothing on NestedInterruptRestoreTPL(TPL_HIGH_LEVEL) To: devel@edk2.groups.io, lersek@redhat.com Cc: Ray Ni , Gerd Hoffmann References: <17ACFF3FDD20CD9A.13754@groups.io> <20240123153104.2451759-1-mcb30@ipxe.org> <0102018d36f278b0-4977df10-4482-4420-bee2-0dee150a9df0-000000@eu-west-1.amazonses.com> From: "Michael Brown" Autocrypt: addr=mcb30@ipxe.org; keydata= xsFNBGPmfF4BEAC3vcU4aLC/9Uy/rTpmYujbqxQNZje9E34jGvLxO3uYwj4BeHj1Nn5T2TDM Gkc4ngk+mGPsJsIn69YU5cfVN+ch9O7FVfsn6egZsCNeLy6Qz0o//gBaWJodFBeawuBjXXyV HnQZa1p7bA/Lws8minW7NrZ7XZgEBaiVm1v1dNbLEoWR8UL2AMtph5loCQ5jPYQNqp/wH9El /R30GjXvAd1riWyJR2TWSN23J9rnuH2Ue+N4yEnWxAsBQ6M/NFQ5z42w4mYdsnzy1w3PulrL icpSixXHkm3lQcKGtKKX41HvJukSpxCgbHfuHGEJZ7bdhgRic1DHKav0JR8kQhx3gnPh06z8 1Teu2NKkSsTR3Iv6E2x6Yy6H34lKWzBzd8TLNSevesDD/L6NU/HxT9AxrTBuypk9PZGe2VH1 W03XnR/0Mnr0QqQBXcIAERdgNzRJY4VKF75vedf8IooZFUQ4RUlqH+x3aZB9nJ9ET77mPaNi SQVQBxE68uzb7eh2Kf6z7ftOYpWPw1v5HyB3oMmafEDG36SIvNF2wnmNaLQDRnAbTcy4ERgy tpJ3wtQDJeXOePLv8hJ3q7DSuePl7cwz4xy0ZHglW/EXRXLnyRRACfDGowyENoStg06qF+qm edGu1wNtmDZ/lypWm/CkzzpUDFeGP5BLZlqwVX4hn88llfvVzwARAQABzR5NaWNoYWVsIEJy b3duIDxtY2IzMEBpcHhlLm9yZz7CwZEEEwEIADsWIQTgD69MBpjBm2slMvwCNbEKAOtEUAUC Y+Z8nwIbAwULCQgHAgIiAgYVCgkICwIEFgIDAQIeBwIXgAAKCRACNbEKAOtEUFlhD/9ElIUg JxBXpIbF8s7u79OdXLld2Z1DfVmhP5Q+GilPvEeAWHhp689S9B88aNvpwW5zJfxlxcJZO0ay jc7E/vtdNrkXGWNEEXBgdve6m+uL+pW/i5E2htqxbLyfgTJKmsvJ8graHbwrrBS/PA8KuwVJ eAGbBNi3f1gyQQWrLqfTkUpLtuj7A76iVVk0G0a78L69Al84qhK2imqpFJoZt1F8h0Z5ddGv mvf2M/DZp87UXvXjy7X6r7msbMZa6S/Jv0dtWHeZGl3Xu3qzbtjlqFyz2Q7TibHiirsgg/CV BsbH/LLbi/aNCCQ/85C6jAMB0lNzcVZ7ZiKKo+vBNMTycDFk70LA9yjlNf7exHejoXmPkLmH ddapYZ4dzwdOiJlaTu8NZgzXUCt3RDDA1qmZrAOBF/F+tPILAEhenl9kj3blD3mPV2SrWLWY dbahY9BsylUhj/qE1ik5CJXrPotmJhok9Vpg07xKDpVnZXuWLGNIE8018UumO7phLrWQwLb1 wJdN7PG165w4UWf4aQphfwaMKOVU3WDghz3aVSP9rgtm3RsUcYHPKx8IaPcDh2yf0bgG386i Axx3U3UQeyz2Pb9Vigo6DmPwXjLkFr/dukvVLVJLVkUab9ZhhERzWTEEMifUVEK2rGNvA87L VKJ2zOyxWx1e0CPj6fcGbkJ0D10XLs7BTQRj5nxeARAAz18zv2ksRiM6eEKG0qzpiKHVYlVy wtjla+m9wuAIwm314tffY5hjQN46uwTstdhQirjywF1EmcS6KNGiIjmoLim+dqyFP5d/UF5A VjLt0TYq7HjadIxbm2/CvcRnNJ01FkD99xLxV0hFTUAWAUX1mNqQ3MmWIjV89wiT06uuAUog m+jG3RRDyWbUnVELR60mhzccKsaEsjO/HqIERvBwL7tlOJewlPrVyz9Zed9Nhhv0KDAYmdEm kIEEbOfsjRu5I6nIY3NrX+QP9+nmgxADlsjvLXTSU0fT/g7IPEl3gpsQZAbgmrlGcPtvXod8 P4iOmL8GJDU1RdBE9TBOLEbu9UlDRD4zr6tdzRpB9wvXdtSUcNCdHVqJTfq2qjIlBk7x+zQD ayhxzDvTMxD/93K6txKXmVVtfMBsmt9KuD2JBUEAExjsLHqzg48nQg8wF9JYWCWGBb36qpd0 yC6VPzhSLe2Ov3/GyV5ZshO046+OiGxEeaHCwMnDTZF9xrQ5paCwWedlWKvGM2zB64AHuk+M v2ABK/gbDO7eS6p+xz11oD1NHr1HQLRtknfClIqj9AmjgX9maD+4GUrmHaxmkNilIukahotd Un9Up2gX05Wy/S3H/v8RB0kxwWg2Wh065dnyCF4Doe18bcYZvM+iMJmUBag6aDfQlryM04K7 z4ITYDkAEQEAAcLBdgQYAQgAIBYhBOAPr0wGmMGbayUy/AI1sQoA60RQBQJj5nxeAhsMAAoJ EAI1sQoA60RQZj4QAIkiRDVNWynZ4kEdpqmf6hpD++Zycz+LMne4iGRsiyyTf/rPNgskNLrU JD555yDvFiEAhOI27R8YNCJj5byXRDa/Bm6ueClFia+POibt28UEdyOFU9PVcgFaU+VxaBIP rHacHL6A7UKFjmBN7o8VkVF2xXlmFge795mP4/Y3t6qfWUTodrpw1w1t5/bZxZdWqX4pUCpY fEx87jm60+Mj0Tb4VPWXz0UD1q1BDcdYxNa2ISLaJhGJmjjks9eqdFOhPo1fTINMNWF2Alxi jA6WNT8nn9lm1kav75EMYMc8WIR9tb03i+IuKNp2IWwTGBqIUyQj00BhHkZQFl4HxZhV0gXE AWu34Q/Z7hOUXGXq2tvYCxDeaQb2wks93e62lrrUm1JGhPWkVoCI8Md8N2mkonqIfMK8lQ0W WbkYHdKBkgDqhDypNNhkjWNX3JL1kL0c3rqGL381iBAZaGQPygyCx2xH9PDNp59W6u8sXb13 +UX+kXdWU+KYbMTVoO/t4MxUJg6nXPJHz9NCkyluI820l+2OtXZZy0u196evIlUdD6RoTrNK z5OgFxNctVi9BPsQea9du+JlYJ460vZNPz180oczj7iqffd+p9DmAkeK25njWhg3qPeXiNZN 45J9eMChSOaJ0GMGUQndIIxz7PO8IzjbkSHLG5CKrR3MaphMB/0L In-Reply-To: X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED,BAYES_00 autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on blyat.fensystems.co.uk Feedback-ID: 1.eu-west-1.fspj4M/5bzJ9NLRzJP0PaxRwxrpZqiDQJ1IF94CF2TA=:AmazonSES X-SES-Outgoing: 2024.01.23-54.240.7.18 Precedence: Bulk List-Subscribe: List-Help: Sender: devel@edk2.groups.io List-Id: Mailing-List: list devel@edk2.groups.io; contact devel+owner@edk2.groups.io Reply-To: devel@edk2.groups.io,mcb30@ipxe.org List-Unsubscribe-Post: List-Unsubscribe=One-Click List-Unsubscribe: X-Gm-Message-State: eBj94flqPjaBPRJfixakkEORx7686176AA= Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-GND-Status: LEGIT Authentication-Results: spool.mail.gandi.net; dkim=pass header.d=groups.io header.s=20140610 header.b=YXjjan07; dmarc=none; spf=pass (spool.mail.gandi.net: domain of bounce@groups.io designates 66.175.222.108 as permitted sender) smtp.mailfrom=bounce@groups.io On 23/01/2024 16:32, Laszlo Ersek wrote: > On 1/23/24 16:31, Michael Brown wrote: >> At TPL_HIGH_LEVEL, CPU interrupts are disabled (as per the UEFI >> specification) and so we should never encounter a situation in which >> an interrupt occurs at TPL_HIGH_LEVEL. >> >> Restoring TPL to TPL_HIGH_LEVEL is always a no-op. Return immediately >> from NestedInterruptRestoreTPL(TPL_HIGH_LEVEL), so that we do not need >> to consider the effect of this possible invariant violation on the >> remainder of the logic. >=20 > Feels like the handling logic might as well be "panic" here (except edk2 > does not have a central panic API that's suitable for all platforms). I > probably missed the previous discussion that led to this patch. Either > way, it seems reasonable. >=20 > Acked-by: Laszlo Ersek Thank you. We can't panic because there are some bootloaders (*cough*=20 Microsoft *cough*) that illegally call RaiseTPL(TPL_HIGH_LEVEL) and then=20 even more illegally enable interrupts via STI. Gerd tracked this down=20 before, which lead to commit https://github.com/tianocore/edk2/commit/bee67e0c1 I found another way to trigger a RestoreTPL(TPL_HIGH_LEVEL) while I was=20 testing the self-tests by deliberately breaking=20 DisableInterruptsOnIret() to fail to disable interrupts. This also=20 induces a situation in which we end up at TPL_HIGH_LEVEL with interrupts=20 enabled. This ended up triggering an assertion (due to the invariant violation)=20 in NestedInterruptRestoreTPL() before reaching the point in the=20 self-test that would have reported a more meaningful error message. Adding the bypass is justifiable on its own merits (as per the reasoning=20 in the commit), and it avoids needing to add clutter to the complex=20 logic in NestedInterruptRestoreTPL() just to ensure that the self-test=20 fails on the desired ASSERT(). I decided against trying to explain all that in the commit message, but=20 I can have a go if you think it needs to be captured. :) Thanks, Michael -=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#114220): https://edk2.groups.io/g/devel/message/114220 Mute This Topic: https://groups.io/mt/103911606/7686176 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [rebecca@openfw.io] -=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-