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Date: Wed, 2 Mar 2016 18:50:21 -0800
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Subject: Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack
From: Yinghai Lu <yinghai@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
        X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Tom Lendacky <thomas.lendacky@amd.com>
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On Wed, Mar 2, 2016 at 5:00 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> On Wed, Mar 2, 2016 at 4:13 PM, Yinghai Lu <yinghai@kernel.org> wrote:
>> On Wed, Mar 2, 2016 at 2:32 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>>>
>>> I'm trying to think of any reason why we couldn't simply have a symbol at the top of the initial stack?  Then a simple leaq would suffice; this is for the BSP after all.
>>
>> Why do we need to call verify_cpu in arch/x86/kernel/head_64.S aka the
>> vmlinux again ?
>>
>> Is that already called in arch/x86/boot/compressed/head_64.S?
>
> that calling is from startup_32, so may add another calling in startup_64,
> so can avoid calling from arch/x86/kernel/head_64.S
>

at the same time, the "call verify_cpu" in
arch/x86/kernel/head_64.s::secondary_startup_64()
is not needed.
As APs already go through
arch/x86/realmode/rm/trampoline_64.S::trampoline_start(), and it
already
call verify_cpu in 16bit mode.

Thanks

Yinghai