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

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Date:   Wed, 14 Jun 2017 14:38:48 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org, Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v6 24/34] x86, swiotlb: Add memory encryption support

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@....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.
>