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 A5437D8042C for ; Tue, 13 Feb 2024 14:02:15 +0000 (UTC) DKIM-Signature: a=rsa-sha256; bh=L02tCfeTLn3x1UPoJ96OJkzlx9yJVr0anrvkm3eYW2Y=; c=relaxed/simple; d=groups.io; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version:In-Reply-To:Precedence:List-Subscribe:List-Help:Sender:List-Id:Mailing-List:Delivered-To:Reply-To:List-Unsubscribe-Post:List-Unsubscribe:Content-Type:Content-Disposition; s=20140610; t=1707832934; v=1; b=QP1+jBUumwbB4QoUXHya4F26wZcI7wKtBfaJ5qXJ/BupFATM9AtBUBhpj+7zIAfXlk/nZjKp Uqr6XX+7QQ5GdngQ72tNUqm9sV0CTpgX7h/IAyTA5kJwbQ1PUsCpO51u6yXeKimDgF0bXeEId4H JfELz7/e/kjdZz+ku2vmYO5E= X-Received: by 127.0.0.2 with SMTP id Rcd9YY7687511xPtNQ7XIXxe; Tue, 13 Feb 2024 06:02:14 -0800 X-Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by mx.groups.io with SMTP id smtpd.web11.12249.1707832933614532576 for ; Tue, 13 Feb 2024 06:02:13 -0800 X-Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-479-oct7KB91M2G29DL92NgeRg-1; Tue, 13 Feb 2024 09:02:10 -0500 X-MC-Unique: oct7KB91M2G29DL92NgeRg-1 X-Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5F94738562C5; Tue, 13 Feb 2024 14:02:10 +0000 (UTC) X-Received: from sirius.home.kraxel.org (unknown [10.39.193.192]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 08888C185C0; Tue, 13 Feb 2024 14:02:10 +0000 (UTC) X-Received: by sirius.home.kraxel.org (Postfix, from userid 1000) id E5FB61800987; Tue, 13 Feb 2024 15:02:08 +0100 (CET) Date: Tue, 13 Feb 2024 15:02:08 +0100 From: "Gerd Hoffmann" To: Laszlo Ersek Cc: devel@edk2.groups.io, Oliver Steffen , Ard Biesheuvel , Jiewen Yao , dun.tan@intel.com Subject: Re: [edk2-devel] [PATCH 1/1] OvmfPkg/QemuVideoDxe: purge VbeShim Message-ID: References: <20240213085925.687848-1-kraxel@redhat.com> <64005185-3cfd-de56-f086-da301aff13ba@redhat.com> MIME-Version: 1.0 In-Reply-To: <64005185-3cfd-de56-f086-da301aff13ba@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com 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,kraxel@redhat.com List-Unsubscribe-Post: List-Unsubscribe=One-Click List-Unsubscribe: X-Gm-Message-State: 1wRAc1CTD6CYxf9TNf2bYGXUx7686176AA= Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-GND-Status: LEGIT Authentication-Results: spool.mail.gandi.net; dkim=pass header.d=groups.io header.s=20140610 header.b=QP1+jBUu; 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=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=redhat.com (policy=none) On Tue, Feb 13, 2024 at 11:44:17AM +0100, Laszlo Ersek wrote: > Hi Gerd, > > On 2/13/24 09:59, Gerd Hoffmann wrote: > > Removing CSM support broke VbeShim. > > > > I see ASSERTS being triggered, both in vbeshim code and elsewhere. > > Didn't investigate in detail, but apparently the real mode address space > > is not considered being special any more, which invalidates some > > assumptions of the vbeshim code. > > > > The guest os which depends on vbeshim for video support is -- according > > to the comments -- Windows 2008 R2. Which went EOL in January 2020, > > more than four years ago. > > > > Time to retire VbeShim. RIP. > > I don't understand this, and/or disagree. > > (1) Please collect more information about the ASSERT()s (the failure mode you are seeing). > Because, (a) in the code that's being removed in this patch, I don't see any ASSERT() that should fire, and (b) I cannot reproduce the issue. (In fact my log contains "InstallVbeShim: VBE shim installed".) Fair enough. The ASSERT() I see firing is this: ASSERT /home/kraxel/projects/edk2/OvmfPkg/QemuVideoDxe/VbeShim.c(142): Int0x10->Segment == 0x0000 It reproduces for me when booting with a bunch of hot-pluggable CPUs (qemu -smp 2,maxcpus=32). I bisected this, and it seems indeed totally unrelated to CSM removal: 725acd0b9cc047b20a1b9379e46f05d3ebcf485e is the first bad commit commit 725acd0b9cc047b20a1b9379e46f05d3ebcf485e Author: Dun Tan Date: Fri Dec 1 10:53:32 2023 +0800 UefiCpuPkg: Avoid assuming only one smmbasehob New theory: This is a NULL pointer dereference corrupting the zero page. I still think it makes sense to retire VbeShim, but of course with a different commit message and also the leftover function declaration removed. Can we unmap the zero page to avoid NULL pointer dereferences going unnoticed (after removing VbeShim)? IIRC I've seen an config option for that a while back, but can't find it now in the source tree ... take care, Gerd -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. 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