linux-kernel - Re: [RFC PATCH] x86: Make sure verify

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Message-ID: <CAE9FiQVz3Ho1TyL9eDmybsvEw=rw7Yrooi6HUxQF-ETkery8Nw@mail.gmail.com>
Date:	Thu, 3 Mar 2016 17:18:34 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Brian Gerst <brgerst@...il.com>,
	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack

On Thu, Mar 3, 2016 at 4:28 AM, Borislav Petkov <bp@...en8.de> wrote:
>
> 04633df0c43d ("x86/cpu: Call verify_cpu() after having entered long mode too")
> added the call to verify_cpu() for sanitizing CPU configuration.
>
> The latter uses the stack minimally and it can happen that we land in
> startup_64() directly from a 64-bit bootloader. Then we want to use our
> own, known good stack.
>
> Do that.
>
> APs don't need this as the trampoline sets up a stack for them.

Even more than that. For AP verify_cpu already get called in trampoline.

arch/x86/realmode/rm/trampoline_64.S::trampoline_start().

So you remove verify_cpu calling in secondary_startup_64.

Yinghai