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

[Borislav Petkov]

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@xxxxxxx>
> ---

...


> 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.

> +
>  /*
>   * 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.

-- 
Regards/Gruss,
    Boris.

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