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Subject: Re: [PATCH 3/3] MdeModulePkg/DxeCore: Unconditionally set memory protections
From: =?UTF-8?B?TWFydmluIEjDpHVzZXI=?= <mhaeuser@posteo.de>
In-Reply-To: <CAMj1kXH90xYGh2v-Qt8FG=R7tH+waCEgSERw9AjadwMRQZ2kmA@mail.gmail.com>
Date: Wed,  8 Feb 2023 18:55:23 +0000
Cc: edk2-devel-groups-io <devel@edk2.groups.io>,
 Michael Kinney <michael.d.kinney@intel.com>,
 Liming Gao <gaoliming@byosoft.com.cn>,
 Jiewen Yao <jiewen.yao@intel.com>,
 Michael Kubacki <michael.kubacki@microsoft.com>,
 Sean Brogan <sean.brogan@microsoft.com>,
 Rebecca Cran <quic_rcran@quicinc.com>,
 Leif Lindholm <quic_llindhol@quicinc.com>,
 Sami Mujawar <sami.mujawar@arm.com>,
 Taylor Beebe <t@taylorbeebe.com>
Message-Id: <76A536C6-42EE-48DB-BF53-810A34E43AE1@posteo.de>
References: <20230208175812.700129-1-ardb@kernel.org>
 <20230208175812.700129-4-ardb@kernel.org>
 <CAMj1kXH90xYGh2v-Qt8FG=R7tH+waCEgSERw9AjadwMRQZ2kmA@mail.gmail.com>
To: Ard Biesheuvel <ardb@kernel.org>
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> On 8. Feb 2023, at 19:49, Ard Biesheuvel <ardb@kernel.org> wrote:
>=20
> This is all copy-pasted from =
MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c

:(

>=20
> The ordering here is a bit tricky. As soon as the CPU arch protocol is
> exposed, every allocation will be remapped individually, resulting in
> page table splits and therefore recursion.

So the issue is the order of event handlers or allocations within the =
event dispatcher? :( Oh lord...

Can we maybe clarify the comment with something like "While =
DxeCore/InitializeDxeNxMemoryProtectionPolicy() would in theory perform =
this task, allocations between the protocol installation and the =
invocation of its event handler may trigger the issue."?=