Subject: Re: [RFC PATCH v3 04/20] x86: Handle reduction in physical address
 size with SME
To: Joerg Roedel <joro@8bytes.org>
References: <20161110003426.3280.2999.stgit@tlendack-t1.amdoffice.net>
 <20161110003513.3280.12104.stgit@tlendack-t1.amdoffice.net>
 <20161115121035.GD24857@8bytes.org>
CC: <linux-arch@vger.kernel.org>, <linux-efi@vger.kernel.org>,
        <kvm@vger.kernel.org>, <linux-doc@vger.kernel.org>, <x86@kernel.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>,
        Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>,
        Matt Fleming <matt@codeblueprint.co.uk>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Larry Woodman <lwoodman@redhat.com>, Ingo Molnar <mingo@redhat.com>,
        Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Dmitry Vyukov <dvyukov@google.com>
From: Tom Lendacky <thomas.lendacky@amd.com>
Message-ID: <f36306aa-cc28-ae2e-1a7e-a6b69c474daf@amd.com>
Date: Tue, 15 Nov 2016 08:32:50 -0600
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101
 Thunderbird/45.4.0
MIME-Version: 1.0
In-Reply-To: <20161115121035.GD24857@8bytes.org>
Content-Type: text/plain; charset="windows-1252"
Content-Transfer-Encoding: 7bit
SpamDiagnosticOutput: 1:99
SpamDiagnosticMetadata: NSPM
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Nov 2016 14:33:01.4548 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR12MB1149
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 927
Lines: 37

On 11/15/2016 6:10 AM, Joerg Roedel wrote:
> On Wed, Nov 09, 2016 at 06:35:13PM -0600, Tom Lendacky wrote:
>> +/*
>> + * AMD Secure Memory Encryption (SME) can reduce the size of the physical
>> + * address space if it is enabled, even if memory encryption is not active.
>> + * Adjust x86_phys_bits if SME is enabled.
>> + */
>> +static void phys_bits_adjust(struct cpuinfo_x86 *c)
>> +{
> 
> Better call this function amd_sme_phys_bits_adjust(). This name makes it
> clear at the call-site why it is there and what it does.

Will do.

> 
>> +	u32 eax, ebx, ecx, edx;
>> +	u64 msr;
>> +
>> +	if (c->x86_vendor != X86_VENDOR_AMD)
>> +		return;
>> +
>> +	if (c->extended_cpuid_level < 0x8000001f)
>> +		return;
>> +
>> +	/* Check for SME feature */
>> +	cpuid(0x8000001f, &eax, &ebx, &ecx, &edx);
>> +	if (!(eax & 0x01))
>> +		return;
> 
> Maybe add a comment here why you can't use cpu_has (yet).
> 

Ok, will do.

Thanks,
Tom