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 for kexec@lists.infradead.org; Thu, 27 Jul 2017 18:48:12 +0000
Subject: Re: [PATCH v1 1/2] x86/mm, kexec: Fix memory corruption with SME on
 successive kexecs
References: <cover.1501092102.git.thomas.lendacky@amd.com>
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From: Tom Lendacky <thomas.lendacky@amd.com>
Message-ID: <a052ad5b-cb70-7279-6837-0cc6e7f8a19c@amd.com>
Date: Thu, 27 Jul 2017 13:47:42 -0500
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>, the arch/x86 maintainers <x86@kernel.org>, Kexec Mailing List <kexec@lists.infradead.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Dave Young <dyoung@redhat.com>, Ingo Molnar <mingo@kernel.org>

On 7/27/2017 12:34 PM, Linus Torvalds wrote:
> On Thu, Jul 27, 2017 at 7:15 AM, Tom Lendacky <thomas.lendacky@amd.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
> 

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