linux-kernel - Re: [PATCH v1 1/2] x86/mm, kexec: Fix memory corruption with SME on successive kexecs

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Date:   Thu, 27 Jul 2017 13:47:42 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Young <dyoung@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH v1 1/2] x86/mm, kexec: Fix memory corruption with SME on
 successive kexecs

On 7/27/2017 12:34 PM, Linus Torvalds wrote:
> On Thu, Jul 27, 2017 at 7:15 AM, Tom Lendacky <thomas.lendacky@....com> wrote:
>>
>> I can #ifdef the wbinvd based on whether AMD_MEM_ENCRYPT is configured
>> or not so that the wbinvd is avoided if not configured.
> 
> I suspect an ifdef will be useless, since things like distro kernels
> tend to enable everything.
> 
> So it should probably be disabled dynamically, and only done if the
> AMD memory encryption thing has actually been active.
> 
> [ There have also been various actual errata with wbinvd, so there
> tends to be a non-performance reason to try to avoid it unless
> strictly required ]

Ok, I'll make the wbinvd a run time decision based on whether SME is
active at the time.

Thanks,
Tom

> 
>                 Linus
>