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[142.162.112.119]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8cda212cac1sm263453685a.33.2026.03.11.17.34.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Mar 2026 17:34:09 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1w0U08-00000006Zyx-3dXg; Wed, 11 Mar 2026 21:34:08 -0300 Date: Wed, 11 Mar 2026 21:34:08 -0300 From: Jason Gunthorpe To: Jiri Pirko Cc: Leon Romanovsky , dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, iommu@lists.linux.dev, linux-media@vger.kernel.org, sumit.semwal@linaro.org, benjamin.gaignard@collabora.com, Brian.Starkey@arm.com, jstultz@google.com, tjmercier@google.com, christian.koenig@amd.com, m.szyprowski@samsung.com, robin.murphy@arm.com, sean.anderson@linux.dev, ptesarik@suse.com, catalin.marinas@arm.com, aneesh.kumar@kernel.org, suzuki.poulose@arm.com, steven.price@arm.com, thomas.lendacky@amd.com, john.allen@amd.com, ashish.kalra@amd.com, suravee.suthikulpanit@amd.com, linux-coco@lists.linux.dev Subject: Re: [PATCH net-next v3 1/2] dma-mapping: introduce DMA_ATTR_CC_DECRYPTED for pre-decrypted memory Message-ID: <20260312003408.GA1469476@ziepe.ca> References: <20260305123641.164164-1-jiri@resnulli.us> <20260305123641.164164-2-jiri@resnulli.us> <20260308101948.GO12611@unreal> <20260309131530.GJ1687929@ziepe.ca> <20260309140233.GW12611@unreal> <20260309151857.GO1687929@ziepe.ca> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Mar 09, 2026 at 06:51:21PM +0100, Jiri Pirko wrote: > Mon, Mar 09, 2026 at 04:18:57PM +0100, jgg@ziepe.ca wrote: > >On Mon, Mar 09, 2026 at 04:02:33PM +0200, Leon Romanovsky wrote: > >> On Mon, Mar 09, 2026 at 10:15:30AM -0300, Jason Gunthorpe wrote: > >> > On Sun, Mar 08, 2026 at 12:19:48PM +0200, Leon Romanovsky wrote: > >> > > >> > > > +/* > >> > > > + * DMA_ATTR_CC_DECRYPTED: Indicates memory that has been explicitly decrypted > >> > > > + * (shared) for confidential computing guests. The caller must have > >> > > > + * called set_memory_decrypted(). A struct page is required. > >> > > > + */ > >> > > > +#define DMA_ATTR_CC_DECRYPTED (1UL << 12) > >> > > > >> > > While adding the new attribute is fine, I would expect additional checks in > >> > > dma_map_phys() to ensure the attribute cannot be misused. For example, > >> > > WARN_ON(attrs & (DMA_ATTR_CC_DECRYPTED | DMA_ATTR_MMIO)), along with a check > >> > > that we are taking the direct path only. > >> > > >> > DECRYPYED and MMIO is something that needs to work, VFIO (inside a > >> > TVM) should be using that combination. > >> > >> So this sentence "A struct page is required" from the comment above is > >> not accurate. > > > >It would be clearer to say "Unless DMA_ATTR_MMIO is provided a struct > >page is required" > > > >We need to audit if that works properly, IIRC it does, but I don't > >remember.. Jiri? > > How can you do set_memory_decrypted if you don't have page/folio ? Alot of device MMIO is decrypted by nature and can't be encrypted, so you'd have to use both flags. eg in VFIO we'd want to do this. Jason