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 for <linuxppc-dev@lists.ozlabs.org>; Mon,  7 Aug 2017 13:49:11 +1000 (AEST)
Date: Mon, 7 Aug 2017 05:48:20 +0200
From: Borislav Petkov <bp@suse.de>
To: Brijesh Singh <brijesh.singh@amd.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linux-efi@vger.kernel.org,
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Subject: Re: [RFC Part1 PATCH v3 12/17] x86/mm: DMA support for SEV memory
 encryption
Message-ID: <20170807034820.GA7521@nazgul.tnic>
References: <20170724190757.11278-1-brijesh.singh@amd.com>
 <20170724190757.11278-13-brijesh.singh@amd.com>
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On Mon, Jul 24, 2017 at 02:07:52PM -0500, Brijesh Singh wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> DMA access to memory mapped as encrypted while SEV is active can not be
> encrypted during device write or decrypted during device read.

Yeah, definitely rewrite that sentence.

> In order
> for DMA to properly work when SEV is active, the SWIOTLB bounce buffers
> must be used.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  arch/x86/mm/mem_encrypt.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++
>  lib/swiotlb.c             |  5 +--
>  2 files changed, 89 insertions(+), 2 deletions

...

> @@ -202,6 +280,14 @@ void __init mem_encrypt_init(void)
>  	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */
>  	swiotlb_update_mem_attributes();
>  
> +	/*
> +	 * With SEV, DMA operations cannot use encryption. New DMA ops
> +	 * are required in order to mark the DMA areas as decrypted or
> +	 * to use bounce buffers.
> +	 */
> +	if (sev_active())
> +		dma_ops = &sme_dma_ops;

Well, we do differentiate between SME and SEV and the check is
sev_active but the ops are called sme_dma_ops. Call them sev_dma_ops
instead for less confusion.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--