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[34.38.181.8]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488ee03898bsm150581075e9.11.2026.04.15.13.27.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Apr 2026 13:27:21 -0700 (PDT) Date: Wed, 15 Apr 2026 20:27:18 +0000 From: Mostafa Saleh To: "Aneesh Kumar K.V" Cc: iommu@lists.linux.dev, linux-kernel@vger.kernel.org, robin.murphy@arm.com, m.szyprowski@samsung.com, will@kernel.org, maz@kernel.org, suzuki.poulose@arm.com, catalin.marinas@arm.com, jiri@resnulli.us, jgg@ziepe.ca Subject: Re: [RFC PATCH v2 2/5] dma-mapping: Use the correct phys_to_dma() for DMA_RESTRICTED_POOL Message-ID: References: <20260330145043.1586623-1-smostafa@google.com> <20260330145043.1586623-3-smostafa@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Apr 13, 2026 at 11:38:36AM +0530, Aneesh Kumar K.V wrote: > Mostafa Saleh writes: > > > As restricted dma pools are always decrypted, in swiotlb.c it uses > > phys_to_dma_unencrypted() for address conversion. > > > > However, in DMA-direct, calls to phys_to_dma_direct() with > > force_dma_unencrypted() returning false, will fallback to > > phys_to_dma() which is inconsistent for memory allocated from > > restricted dma pools. > > > > Fixes: f4111e39a52a ("swiotlb: Add restricted DMA alloc/free support") > > Signed-off-by: Mostafa Saleh > > --- > > kernel/dma/direct.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > > index 27d804f0473f..1a402bb956d9 100644 > > --- a/kernel/dma/direct.c > > +++ b/kernel/dma/direct.c > > @@ -26,7 +26,7 @@ u64 zone_dma_limit __ro_after_init = DMA_BIT_MASK(24); > > static inline dma_addr_t phys_to_dma_direct(struct device *dev, > > phys_addr_t phys) > > { > > - if (force_dma_unencrypted(dev)) > > + if (force_dma_unencrypted(dev) || is_swiotlb_for_alloc(dev)) > > return phys_to_dma_unencrypted(dev, phys); > > > > So what kind of device is this? Is it a trusted device that needs to use > swiotlb in unencrypted form?(is that a valid use case?) Can we add additional comment > explaining the type of device for which we are allocating the DMA > buffer? That’s used for devices that use restricted-dma pools which are currently always decrypted, typically virtio devices that are emulated by the untrusted host. Thanks, Mostafa > > > return phys_to_dma(dev, phys); > > } > > -- > > 2.53.0.1185.g05d4b7b318-goog > > -aneesh