Re: [RFC Part1 PATCH v3 06/17] x86/mm: Use encrypted access of boot related data with SEV

[Tom Lendacky <thomas.lendacky@amd.com>]

On 7/27/2017 8:31 AM, Borislav Petkov wrote:
> On Mon, Jul 24, 2017 at 02:07:46PM -0500, Brijesh Singh wrote:
>> From: Tom Lendacky <thomas.lendacky@amd.com>
>>
>> When Secure Encrypted Virtualization (SEV) is active, boot data (such as
>> EFI related data, setup data) is encrypted and needs to be accessed as
>> such when mapped. Update the architecture override in early_memremap to
>> keep the encryption attribute when mapping this data.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>> ---
>>   arch/x86/mm/ioremap.c | 44 ++++++++++++++++++++++++++++++++------------
>>   1 file changed, 32 insertions(+), 12 deletions(-)
> 
> ...
> 
>> @@ -590,10 +598,15 @@ bool arch_memremap_can_ram_remap(resource_size_t phys_addr, unsigned long size,
>>   	if (flags & MEMREMAP_DEC)
>>   		return false;
>>   
>> -	if (memremap_is_setup_data(phys_addr, size) ||
>> -	    memremap_is_efi_data(phys_addr, size) ||
>> -	    memremap_should_map_decrypted(phys_addr, size))
>> -		return false;
>> +	if (sme_active()) {
>> +		if (memremap_is_setup_data(phys_addr, size) ||
>> +		    memremap_is_efi_data(phys_addr, size) ||
>> +		    memremap_should_map_decrypted(phys_addr, size))
>> +			return false;
>> +	} else if (sev_active()) {
>> +		if (memremap_should_map_decrypted(phys_addr, size))
>> +			return false;
>> +	}
>>   
>>   	return true;
>>   }
> 
> I guess this function's hind part can be simplified to:
> 
>          if (sme_active()) {
>                  if (memremap_is_setup_data(phys_addr, size) ||
>                      memremap_is_efi_data(phys_addr, size))
>                          return false;
>          }
> 
>          return ! memremap_should_map_decrypted(phys_addr, size);
> }
> 

Ok, definitely cleaner.

>> @@ -608,15 +621,22 @@ pgprot_t __init early_memremap_pgprot_adjust(resource_size_t phys_addr,
>>   					     unsigned long size,
>>   					     pgprot_t prot)
> 
> And this one in a similar manner...
> 
>>   {
>> -	if (!sme_active())
>> +	if (!sme_active() && !sev_active())
>>   		return prot;
> 
> ... and you don't need that check...
> 
>> -	if (early_memremap_is_setup_data(phys_addr, size) ||
>> -	    memremap_is_efi_data(phys_addr, size) ||
>> -	    memremap_should_map_decrypted(phys_addr, size))
>> -		prot = pgprot_decrypted(prot);
>> -	else
>> -		prot = pgprot_encrypted(prot);
>> +	if (sme_active()) {
> 
> ... if you're going to do it here too.
> 
>> +		if (early_memremap_is_setup_data(phys_addr, size) ||
>> +		    memremap_is_efi_data(phys_addr, size) ||
>> +		    memremap_should_map_decrypted(phys_addr, size))
>> +			prot = pgprot_decrypted(prot);
>> +		else
>> +			prot = pgprot_encrypted(prot);
>> +	} else if (sev_active()) {
> 
> And here.

Will do.

Thanks,
Tom

> 
>> +		if (memremap_should_map_decrypted(phys_addr, size))
>> +			prot = pgprot_decrypted(prot);
>> +		else
>> +			prot = pgprot_encrypted(prot);
>> +	}
>