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 F0FE9D8003E for ; Sat, 20 Jan 2024 00:49:34 +0000 (UTC) DKIM-Signature: a=rsa-sha256; bh=tRysw4ccI6XiDyAHdJD2NQ/zpq7tjGs0lINGUhhgsZ0=; 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=1705711773; v=1; b=dQRMG3fswZCOFBmaNXfvV8Iv7CB6j7yiK5XJfVENmJwKK208lqsubeY7RWa0pIBjHxZC1b54 P53P5kin3OXMGTDXJ3d/Z6XReokJYEYLboW0SX0ws5tckudTWfx9EaplDp6teLOoW43y01AZCYO ANiZ4LolJu3Pg1wxWuIBs9Uk= X-Received: by 127.0.0.2 with SMTP id 2C7fYY7687511xphRVPXcfJB; Fri, 19 Jan 2024 16:49:33 -0800 X-Received: from a7-10.smtp-out.eu-west-1.amazonses.com (a7-10.smtp-out.eu-west-1.amazonses.com [54.240.7.10]) by mx.groups.io with SMTP id smtpd.web10.10859.1705711772268887821 for ; Fri, 19 Jan 2024 16:49:32 -0800 Message-ID: <0102018d24581b55-17b57f2c-d3ad-4383-bb46-62508c0200b2-000000@eu-west-1.amazonses.com> Date: Sat, 20 Jan 2024 00:49:30 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [edk2-devel] [PATCH 1/6] UefiCpuPkg/LocalApicTimerDxe: Duplicate OvmfPkg/LocalApicTimerDxe driver To: devel@edk2.groups.io, ray.ni@intel.com, Laszlo Ersek , "kraxel@redhat.com" Cc: Pedro Falcato , "Kinney, Michael D" , "Desimone, Nathaniel L" , "Kumar, Rahul R" , "Liu, Zhiguang" References: <20240115080325.147-1-ray.ni@intel.com> <20240115080325.147-2-ray.ni@intel.com> <0102018d11ac8fe8-1ce1e102-af57-426f-bafc-7297bec4799a-000000@eu-west-1.amazonses.com> <0102018d12d8bd9f-d209332f-f501-498e-b43c-3b0cc4f7ef7b-000000@eu-west-1.amazonses.com> <0102018d17080a28-370d97eb-b73c-4811-a9ea-05cfb459ba37-000000@eu-west-1.amazonses.com> <0102018d22d0f904-3aa0bdff-abe9-4c74-8316-0dc17122f372-000000@eu-west-1.amazonses.com> From: "Michael Brown" Autocrypt: addr=mcb30@ipxe.org; 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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: R6tfUQkV8tFt9P66C5w5qWmbx7686176AA= 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=dQRMG3fs; spf=pass (spool.mail.gandi.net: domain of bounce@groups.io designates 66.175.222.108 as permitted sender) smtp.mailfrom=bounce@groups.io; dmarc=none On 19/01/2024 23:44, Ni, Ray wrote: > I still want to see if the RestoreTpl2 that does not enable interrupt is= =20 > added as a protocol, and how simple the lib could be. RestoreTpl() always has to enable interrupts during its execution, since=20 interrupts must be allowed to occur while callbacks are running=20 (otherwise the callbacks may break due to the system time freezing). The only alternative approach I am aware of would be to add a=20 RestoreTPLEx() call to EFI_BOOT_SERVICES, with an additional parameter=20 EnableInterruptsAtRestoredTpl. RestoreTPLEx() would then: 1. For each TPL between EfiCurrentTpl and OldTpl: a) enable interrupts b) dispatch any callbacks registered at this TPL c) disable interrupts 2. Re-enable interrupts before returning if=20 EnableInterruptsAtRestoredTpl is TRUE. The implementation of RestoreTPL() would then become just a call to=20 RestoreTPLEx(OldTPl, (OldTpl < TPL_HIGH_LEVEL)). This would require a change to the EFI_BOOT_SERVICES table definition,=20 which is something that I don't think has happened in the 18 years since=20 the UEFI specification was released. There's a very good chance that=20 such a table change would break something, somewhere. RestoreTPLEx() could be installed as a protocol instead, but it seems=20 very messy to have something so fundamental as TPL management and event=20 dispatch handled through an installable (and therefore uninstallable)=20 protocol. Are there any other instances where deep internals of DxeCore=20 are exposed in this way? Lastly: I think the RestoreTPLEx approach ought to work, but I have not=20 done any testing on it (and have no intention of trying it, unless Intel=20 wants to fund the work). NestedInterruptTplLib has been quite=20 thoroughly tested by now. > The reason is about maintainability. > I can image that one day people would question the Lib implementation if= =20 > some timer event issue appears. If the Lib is easy to understand, the=20 > suspicion could be avoided. > And if the correctness of the Lib can be proven by a thorough test, that= =20 > will be better. But it seems to me the Lib can only be proven as correct= =20 > with careful code review, like some multi-threaded logic. It's relatively easy to test with a deliberately broken ISR: that's how=20 I tested it during development. The semi-formal proof is an added bonus. Testing shows that the=20 symptoms have gone away, but the semi-formal proof is what gives=20 confidence (to me, at least) that the problem has actually been fixed=20 properly. 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 (#114104): https://edk2.groups.io/g/devel/message/114104 Mute This Topic: https://groups.io/mt/103734961/7686176 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-