Subject: Re: [RFC Part1 PATCH v3 07/17] x86/mm: Include SEV for encryption
 memory attribute changes
To: David Laight <David.Laight@ACULAB.COM>,
        "'Borislav Petkov'" <bp@suse.de>,
        Brijesh Singh <brijesh.singh@amd.com>
Cc: "linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
        =?UTF-8?Q?Radim_Krcm=c3=a1r?= <rkrcmar@redhat.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Matt Fleming <matt@codeblueprint.co.uk>,
        David Howells <dhowells@redhat.com>, Paul Mackerras <paulus@samba.org>,
        "H . Peter Anvin" <hpa@zytor.com>, Christoph Lameter <cl@linux.com>,
        Jonathan Corbet <corbet@lwn.net>, "x86@kernel.org" <x86@kernel.org>,
        Piotr Luc <piotr.luc@intel.com>, Ingo Molnar <mingo@redhat.com>,
        Dave Airlie <airlied@redhat.com>, Laura Abbott <labbott@redhat.com>,
        Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
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        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Tony Luck <tony.luck@intel.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
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        Eric Biederman <ebiederm@xmission.com>, Tejun Heo <tj@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Lu Baolu <baolu.lu@linux.intel.com>
References: <20170724190757.11278-1-brijesh.singh@amd.com>
 <20170724190757.11278-8-brijesh.singh@amd.com>
 <20170727145841.GG28553@nazgul.tnic>
 <063D6719AE5E284EB5DD2968C1650D6DD0045508@AcuExch.aculab.com>
From: Tom Lendacky <thomas.lendacky@amd.com>
Message-ID: <786b615a-941c-ae83-e02b-01ece58af5b3@amd.com>
Date: Thu, 17 Aug 2017 13:21:39 -0500
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On 7/28/2017 3:47 AM, David Laight wrote:
> From: Borislav Petkov
>> Sent: 27 July 2017 15:59
>> 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 ...
> 
> If any of the code paths are 'hot' it would make sense to be checking
> a single memory location.

The function would check a single variable/memory location and making it
an inline function would accomplish that.

Thanks,
Tom

> 
> 	David
>