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Date: Wed, 1 May 2024 11:17:37 -0300
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: linux-kernel@vger.kernel.org, iommu@lists.linux.dev, joro@8bytes.org,
	thomas.lendacky@amd.com, vasant.hegde@amd.com, michael.roth@amd.com,
	jon.grimm@amd.com, rientjes@google.com
Subject: Re: [PATCH 9/9] iommu/amd: Set default domain to IDENTITY_DOMAIN
 when running in SEV guest
Message-ID: <20240501141737.GB1723318@ziepe.ca>
References: <20240430152430.4245-1-suravee.suthikulpanit@amd.com>
 <20240430152430.4245-10-suravee.suthikulpanit@amd.com>
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In-Reply-To: <20240430152430.4245-10-suravee.suthikulpanit@amd.com>

On Tue, Apr 30, 2024 at 03:24:30PM +0000, Suravee Suthikulpanit wrote:
> Since SEV guest depends on the unencrypted swiotlb bounce buffer
> to support DMA, the guest AMD IOMMU driver must be force to setup to
> pass-through mode.

You should block the creation of paging domains as well if the HW
can't support them.

But, is there actually a functional problem here? Doesn't swiotlb work
OK with iommu even with the encrypted memory cases? What is missing if
not?

Jason