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

[Tom Lendacky]

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@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.

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.