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

Tom Lendacky
2017-08-17T18:21:39Z

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-5C7GfCeVMHo@public.gmane.org>
>>>
>>> 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-5C7GfCeVMHo@public.gmane.org>
>>> Signed-off-by: Brijesh Singh <brijesh.singh-5C7GfCeVMHo@public.gmane.org>
>>> ---
>>> 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
>