Re: [PATCH v6 24/34] x86, swiotlb: Add memory encryption support

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

On 6/14/2017 11:45 AM, Borislav Petkov wrote:
> On Wed, Jun 07, 2017 at 02:17:21PM -0500, Tom Lendacky wrote:
>> Since DMA addresses will effectively look like 48-bit addresses when the
>> memory encryption mask is set, SWIOTLB is needed if the DMA mask of the
>> device performing the DMA does not support 48-bits. SWIOTLB will be
>> initialized to create decrypted bounce buffers for use by these devices.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
> 
> ...
> 
> 
>> diff --git a/init/main.c b/init/main.c
>> index df58a41..7125b5f 100644
>> --- a/init/main.c
>> +++ b/init/main.c
>> @@ -488,6 +488,10 @@ void __init __weak thread_stack_cache_init(void)
>>   }
>>   #endif
>>   
>> +void __init __weak mem_encrypt_init(void)
>> +{
>> +}
> 
> void __init __weak mem_encrypt_init(void) { }
> 
> saves some real estate. Please do that for the rest of the stubs you're
> adding, for the next version.

Ok, will do.

Thanks,
Tom

> 
>> +
>>   /*
>>    * Set up kernel memory allocators
>>    */
>> @@ -640,6 +644,15 @@ asmlinkage __visible void __init start_kernel(void)
>>   	 */
>>   	locking_selftest();
>>   
>> +	/*
>> +	 * This needs to be called before any devices perform DMA
>> +	 * operations that might use the SWIOTLB bounce buffers.
>> +	 * This call will mark the bounce buffers as decrypted so
>> +	 * that their usage will not cause "plain-text" data to be
>> +	 * decrypted when accessed.
> 
> s/This call/It/
> 
>> +	 */
>> +	mem_encrypt_init();
>> +
>>   #ifdef CONFIG_BLK_DEV_INITRD
>>   	if (initrd_start && !initrd_below_start_ok &&
>>   	    page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
>> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
>> index a8d74a7..74d6557 100644
>> --- a/lib/swiotlb.c
>> +++ b/lib/swiotlb.c
>> @@ -30,6 +30,7 @@
>>   #include <linux/highmem.h>
>>   #include <linux/gfp.h>
>>   #include <linux/scatterlist.h>
>> +#include <linux/mem_encrypt.h>
>>   
>>   #include <asm/io.h>
>>   #include <asm/dma.h>
>> @@ -155,6 +156,17 @@ unsigned long swiotlb_size_or_default(void)
>>   	return size ? size : (IO_TLB_DEFAULT_SIZE);
>>   }
>>   
>> +void __weak swiotlb_set_mem_attributes(void *vaddr, unsigned long size)
>> +{
>> +}
> 
> As above.
>