Subject: Re: [RFC Part1 PATCH v3 07/17] x86/mm: Include SEV for encryption
 memory attribute changes
To: Borislav Petkov <bp@suse.de>, Brijesh Singh <brijesh.singh@amd.com>
Cc: 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>
 <20170724190757.11278-8-brijesh.singh@amd.com>
 <20170727145841.GG28553@nazgul.tnic>
From: Tom Lendacky <thomas.lendacky@amd.com>
Message-ID: <a1daf0f5-57cb-d9c3-79f7-3d4852c35974@amd.com>
Date: Thu, 17 Aug 2017 13:10:45 -0500
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On 7/27/2017 9:58 AM, Borislav Petkov wrote:
> On Mon, Jul 24, 2017 at 02:07:47PM -0500, Brijesh Singh wrote:
>> From: Tom Lendacky <thomas.lendacky@amd.com>
>>
>> The current code checks only for sme_active() when determining whether
>> to perform the encryption attribute change.  Include sev_active() in this
>> check so that memory attribute changes can occur under SME and SEV.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>> ---
>>   arch/x86/mm/pageattr.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
>> index dfb7d65..b726b23 100644
>> --- a/arch/x86/mm/pageattr.c
>> +++ b/arch/x86/mm/pageattr.c
>> @@ -1781,8 +1781,8 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
>>   	unsigned long start;
>>   	int ret;
>>   
>> -	/* Nothing to do if the SME is not active */
>> -	if (!sme_active())
>> +	/* Nothing to do if SME and SEV are not active */
>> +	if (!sme_active() && !sev_active())
> 
> This is the second place which does
> 
> 	if (!SME && !SEV)
> 
> I wonder if, instead of sprinking those, we should have a
> 
> 	if (mem_enc_active())
> 
> or so which unifies all those memory encryption logic tests and makes
> the code more straightforward for readers who don't have to pay
> attention to SME vs SEV ...

Yup, that will make things look cleaner and easier to understand.

Thanks,
Tom

> 
> Just a thought.
>