Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 27 Oct 2022 17:33:59 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Martin Fernandez <martin.fernandez@eclypsium.com>,
        linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org,
        platform-driver-x86@vger.kernel.org, linux-mm@kvack.org,
        kunit-dev@googlegroups.com, linux-kselftest@vger.kernel.org,
        tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com,
        x86@kernel.org, hpa@zytor.com, ardb@kernel.org,
        dvhart@infradead.org, andy@infradead.org,
        gregkh@linuxfoundation.org, rafael@kernel.org, rppt@kernel.org,
        akpm@linux-foundation.org, daniel.gutson@eclypsium.com,
        hughsient@gmail.com, alex.bazhaniuk@eclypsium.com,
        alison.schofield@intel.com, keescook@chromium.org
Subject: Re: [PATCH v9 0/9] x86: Show in sysfs if a memory node is able to do
 encryption
Message-ID: <Y1qk56DGw00IyjU0@zn.tnic>
References: <20220704135833.1496303-1-martin.fernandez@eclypsium.com>
 <Y0hrhzprPFTK+VWV@zn.tnic>
 <CAKgze5ajp-z0+F+8Qo2z=834=i=HNa5=s54MLyrk16wQVnxCzQ@mail.gmail.com>
 <Y1pH/DuYJeo7Kyo5@zn.tnic>
 <6758af9b-1110-ad5a-3961-e256d5c8d576@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <6758af9b-1110-ad5a-3961-e256d5c8d576@intel.com>
Precedence: bulk

On Thu, Oct 27, 2022 at 08:21:02AM -0700, Dave Hansen wrote:
> On 10/27/22 01:57, Borislav Petkov wrote:
> > Well, I still think this is not going to work in all cases. SME/TME can
> > be enabled but the kernel can go - and for whatever reason - map a bunch
> > of memory unencrypted.
> 
> For TME on Intel systems, there's no way to make it unencrypted.  The
> memory controller is doing all the encryption behind the back of the OS
> and even devices that are doing DMA.  Nothing outside of the memory
> controller really knows or cares that encryption is happening.

Ok, Tom just confirmed that AMD's TSME thing also encrypts all memory.

So I guess the code should check for TME or TSME. If those are set, then
you can assume that all memory is encrypted.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette