linux-kernel - Re: [PATCH] efi/x86: use naked RET on mixed mode call wrapper

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Message-ID: <YtWF/GLXxBNQjkOX@worktop.programming.kicks-ass.net>
Date:   Mon, 18 Jul 2022 18:10:36 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Cc:     linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        x86@...nel.org, ardb@...nel.org, tglx@...utronix.de,
        gregkh@...uxfoundation.org, torvalds@...ux-foundation.org,
        Guenter Roeck <linux@...ck-us.net>,
        Borislav Petkov <bp@...e.de>,
        Josh Poimboeuf <jpoimboe@...nel.org>, stable@...r.kernel.org,
        Andrew Cooper <Andrew.Cooper3@...rix.com>
Subject: Re: [PATCH] efi/x86: use naked RET on mixed mode call wrapper

On Mon, Jul 18, 2022 at 10:59:18AM -0300, Thadeu Lima de Souza Cascardo wrote:

> And I think you nailed what I had in mind for using IBPB when doing firmware
> calls, and perhaps this is wanted even when we ignore this naked RET here.
> 
> There is a typo on your patch below, but I will give it a try and see if it
> doesn't blow up on AMD systems without IBPB (by way of emulation).

Yeah, Boris pointed out the same. Typing is hard ;-)