linux-kernel - Re: [PATCH 1/1] drm/ttm: Set memory as decrypted for ttm framebuffer mappings

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Date:   Wed, 22 Aug 2018 21:09:36 +0200
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Jiandi An <jiandi.an@....com>, dri-devel@...ts.freedesktop.org
Cc:     airlied@...ux.ie, linux-kernel@...r.kernel.org, ray.huang@....com,
        Jerry.Zhang@....com, christian.koenig@....com
Subject: Re: [PATCH 1/1] drm/ttm: Set memory as decrypted for ttm framebuffer
 mappings

Am 22.08.2018 um 20:57 schrieb Jiandi An:
> Framebuffer memory needs to be accessed decrypted.  Ensure the
> memory encryption mask is not set for the ttm framebuffer mappings.

NAK, the memory not only needs to be decrypted while CPU accessed but 
all the time.

ttm_page_alloc.c and ttm_page_alloc_dma.c should already take care of 
that while mapping the pages.

Regards,
Christian.

>
> Signed-off-by: Jiandi An <jiandi.an@....com>
> ---
>   drivers/gpu/drm/ttm/ttm_bo_util.c | 12 +++++++++++-
>   drivers/gpu/drm/ttm/ttm_bo_vm.c   |  6 ++++--
>   2 files changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> index 046a6dda690a..b3f5d26f571e 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> @@ -29,6 +29,7 @@
>    * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
>    */
>   
> +#include <asm/set_memory.h>
>   #include <drm/ttm/ttm_bo_driver.h>
>   #include <drm/ttm/ttm_placement.h>
>   #include <drm/drm_vma_manager.h>
> @@ -639,7 +640,11 @@ int ttm_bo_kmap(struct ttm_buffer_object *bo,
>   	if (ret)
>   		return ret;
>   	if (!bo->mem.bus.is_iomem) {
> -		return ttm_bo_kmap_ttm(bo, start_page, num_pages, map);
> +		ret = ttm_bo_kmap_ttm(bo, start_page, num_pages, map);
> +		if (!ret && sev_active())
> +			set_memory_decrypted((unsigned long) map->virtual,
> +					     num_pages);
> +		return ret;
>   	} else {
>   		offset = start_page << PAGE_SHIFT;
>   		size = num_pages << PAGE_SHIFT;
> @@ -661,9 +666,14 @@ void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map)
>   		iounmap(map->virtual);
>   		break;
>   	case ttm_bo_map_vmap:
> +		if (sev_active())
> +			set_memory_encrypted((unsigned long) map->virtual,
> +					     bo->num_pages);
>   		vunmap(map->virtual);
>   		break;
>   	case ttm_bo_map_kmap:
> +		if (sev_active())
> +			set_memory_encrypted((unsigned long) map->virtual, 1);
>   		kunmap(map->page);
>   		break;
>   	case ttm_bo_map_premapped:
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index 6fe91c1b692d..211d3549fd9f 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -249,10 +249,12 @@ static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
>   	 * Speculatively prefault a number of pages. Only error on
>   	 * first page.
>   	 */
> +
> +	/* Mark framebuffer pages decrypted */
> +	cvma.vm_page_prot = pgprot_decrypted(cvma.vm_page_prot);
> +
>   	for (i = 0; i < TTM_BO_VM_NUM_PREFAULT; ++i) {
>   		if (bo->mem.bus.is_iomem) {
> -			/* Iomem should not be marked encrypted */
> -			cvma.vm_page_prot = pgprot_decrypted(cvma.vm_page_prot);
>   			pfn = ttm_bo_io_mem_pfn(bo, page_offset);
>   		} else {
>   			page = ttm->pages[page_offset];