From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH v5 28/32] x86/mm, kexec: Allow kexec to be used with SME
Date: Fri, 19 May 2017 16:38:07 -0500
Message-ID: <8baa170c-f0bd-3e5d-17d9-a031f4ff943c@amd.com>
References: <20170418211612.10190.82788.stgit@tlendack-t1.amdoffice.net>
 <20170418212121.10190.94885.stgit@tlendack-t1.amdoffice.net>
 <20170517191755.h2xluopk2p6suw32@pd.tnic>
 <1b74e0e6-3dda-f638-461b-f73af9904360@amd.com>
 <20170519205836.3wvl3nztqyyouje3@pd.tnic>
 <5ef96f3a-6ebd-1d4d-7ac9-05dbed45d998@amd.com>
 <20170519212854.3dvtt3lawzij5cae@pd.tnic>
Mime-Version: 1.0
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 7bit
Return-path: <owner-linux-mm@kvack.org>
In-Reply-To: <20170519212854.3dvtt3lawzij5cae@pd.tnic>
Sender: owner-linux-mm@kvack.org
To: Borislav Petkov <bp@alien8.de>
Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Rik van Riel <riel@redhat.com>, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>, Toshimitsu Kani <toshi.kani@hpe.com>, Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>, Matt Fleming <matt@codeblueprint.co.uk>, "Michael S.
 Tsirkin" <mst@redhat.com>, Joerg Roedel <joro@8bytes.org>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Paolo Bonzini <pbonzini@redhat.com>, Larry Woodman <lwoodman@redhat.com>, Brijesh Singh <brijesh.singh@amd.com>, Ingo Molnar <mingo@redhat.com>, Andy Lutomirski <luto@kernel.org>, "H. Peter
 Anvin" <hpa@zytor.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>
List-Id: linux-efi@vger.kernel.org

On 5/19/2017 4:28 PM, Borislav Petkov wrote:
> On Fri, May 19, 2017 at 04:07:24PM -0500, Tom Lendacky wrote:
>> As long as those never change from static inline everything will be
>> fine. I can change it, but I really like how it explicitly indicates
>
> I know what you want to do. But you're practically defining a helper
> which contains two arbitrary instructions which probably no one else
> will need.
>
> So how about we simplify this function even more. We don't need to pay
> attention to kexec being in progress because we're halting anyway so who
> cares how fast we halt.
>
> Might have to state that in the comment below though, instead of what's
> there now.
>
> And for the exact same moot reason, we don't need to look at SME CPUID
> feature - we can just as well WBINVD unconditionally.
>
> void stop_this_cpu(void *dummy)
> {
>         local_irq_disable();
>         /*
>          * Remove this CPU:
>          */
>         set_cpu_online(smp_processor_id(), false);
>         disable_local_APIC();
>         mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
>
>         for (;;) {
>                 /*
>                  * If we are performing a kexec and the processor supports
>                  * SME then we need to clear out cache information before
>                  * halting. With kexec, going from SME inactive to SME active
>                  * requires clearing cache entries so that addresses without
>                  * the encryption bit set don't corrupt the same physical
>                  * address that has the encryption bit set when caches are
>                  * flushed. Perform a wbinvd followed by a halt to achieve
>                  * this.
>                  */
>                 asm volatile("wbinvd; hlt" ::: "memory");
>         }
> }
>
> How's that?

I can live with that!

Thanks,
Tom

>

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>