Subject: Re: [RFC Part1 PATCH v3 07/17] x86/mm: Include SEV for encryption memory attribute changes

From: Tom Lendacky <[email-masked]>
Date: Thu, 17 Aug 2017 13:21:39 -0500

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 <[email-masked]>
>>>
>>> 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 <[email-masked]>
>>> Signed-off-by: Brijesh Singh <[email-masked]>
>>> ---
>>>   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