linux-kernel - Re: [PATCH v5 32/32] x86/mm: Add support to make use of Secure Memory Encryption

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Message-ID: <1ac40d18-a8b2-94eb-35ed-c30768667be8@amd.com>
Date:   Tue, 30 May 2017 10:48:27 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Borislav Petkov <bp@...en8.de>
CC:     <linux-arch@...r.kernel.org>, <linux-efi@...r.kernel.org>,
        <kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <x86@...nel.org>, <kexec@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kasan-dev@...glegroups.com>,
        <linux-mm@...ck.org>, <iommu@...ts.linux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 32/32] x86/mm: Add support to make use of Secure Memory
 Encryption

On 5/19/2017 3:16 PM, Josh Poimboeuf wrote:
> On Fri, May 19, 2017 at 01:30:05PM +0200, Borislav Petkov wrote:
>>> it is called so early. I can get past it by adding:
>>>
>>> CFLAGS_mem_encrypt.o := $(nostackp)
>>>
>>> in the arch/x86/mm/Makefile, but that obviously eliminates the support
>>> for the whole file.  Would it be better to split out the sme_enable()
>>> and other boot routines into a separate file or just apply the
>>> $(nostackp) to the whole file?
>>
>> Josh might have a better idea here... CCed.
> 
> I'm the stack validation guy, not the stack protection guy :-)
> 
> But there is a way to disable compiler options on a per-function basis
> with the gcc __optimize__ function attribute.  For example:
> 
>    __attribute__((__optimize__("no-stack-protector")))
> 

I'll look at doing that instead of removing the support for the whole
file.

Thanks,
Tom