Subject: Re: [RFC Part1 PATCH v3 02/17] x86/CPU/AMD: Add the Secure Encrypted
 Virtualization CPU feature
To: Borislav Petkov <bp@suse.de>
Cc: Brijesh Singh <brijesh.singh@amd.com>, linux-kernel@vger.kernel.org,
        x86@kernel.org, linux-efi@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H . Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>,
        Tony Luck <tony.luck@intel.com>, Piotr Luc <piotr.luc@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>, Lu Baolu <baolu.lu@linux.intel.com>,
        Reza Arbab <arbab@linux.vnet.ibm.com>,
        David Howells <dhowells@redhat.com>,
        Matt Fleming <matt@codeblueprint.co.uk>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Laura Abbott <labbott@redhat.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Eric Biederman <ebiederm@xmission.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Jonathan Corbet <corbet@lwn.net>, Dave Airlie <airlied@redhat.com>,
        Kees Cook <keescook@chromium.org>, Paolo Bonzini <pbonzini@redhat.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Arnd Bergmann <arnd@arndb.de>, Tejun Heo <tj@kernel.org>,
        Christoph Lameter <cl@linux.com>
References: <20170724190757.11278-1-brijesh.singh@amd.com>
 <20170724190757.11278-3-brijesh.singh@amd.com>
 <20170725102657.GD21822@nazgul.tnic>
 <7236d267-ebcb-8b45-b8d3-5955903e395f@amd.com>
 <20170725143615.GA26029@nazgul.tnic>
 <47ccc32e-e113-48e0-d2e0-2f23b37cc452@amd.com>
 <20170725151301.GC26029@nazgul.tnic>
 <d6fdba78-034b-d9e2-15ae-00547821a855@amd.com>
 <20170725153329.GE26029@nazgul.tnic>
From: Tom Lendacky <thomas.lendacky@amd.com>
Message-ID: <b2aedd44-ebbc-b196-31d0-0b423f4fa632@amd.com>
Date: Wed, 9 Aug 2017 13:17:54 -0500
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On 7/25/2017 10:33 AM, Borislav Petkov wrote:
> On Tue, Jul 25, 2017 at 10:29:40AM -0500, Tom Lendacky wrote:
>> But early_identify_cpu() calls get_cpu_cap() which will check for cpuid
>> leaf 0x80000008 support and set x86_phys_bits.
> 
> Right, but it can't be less than 32, can it? And if it is more than 32
> bits, then it probably doesn't really matter on 32-bit. Unless it is
> less than 36 bits and you do PAE...
> 
>> I'll try to build and run a 32-bit kernel and see how this all flows.
> 
> Yeah, that would be good.

Ok, finally got around to running a 32-bit kernel and it reports
x86_phys_bits as 48.

Thanks,
Tom

> 
> Thanks.
>