linux-kernel - Re: [PATCH] x86/efi: Restore Firmware IDT in before ExitBootServices()

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Message-ID: <YR+Bxgq4aIo1DI8j@8bytes.org>
Date:   Fri, 20 Aug 2021 12:19:50 +0200
From:   'Joerg Roedel' <joro@...tes.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     "x86@...nel.org" <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "hpa@...or.com" <hpa@...or.com>, Joerg Roedel <jroedel@...e.de>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>,
        Uros Bizjak <ubizjak@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Ard Biesheuvel <ardb@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Fabio Aiuto <fabioaiuto83@...il.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] x86/efi: Restore Firmware IDT in before
 ExitBootServices()

On Fri, Aug 20, 2021 at 09:02:46AM +0000, David Laight wrote:
> So allocate and initialise the Linux IDT - so entries can be added.
> But don't execute 'lidt' until later on.

The IDT is needed in this path to handle #VC exceptions caused by CPUID
instructions. So loading the IDT later is not an option.

Regards,

	Joerg