From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0C16C312807; Wed, 1 Jul 2026 05:51:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782885084; cv=none; b=ufABZM03tFrGvmabIjJiMIvEyh0p/gXLkIk1ulJ91ZjpqwnESUwDASI5YYYMClWuzcpc1KgMjHwd+sj2oEpKkiUuYeUYxRshQOkjsssKJsCFloba4dUE5CMpFUBfyFwealzI7M2jFBqsA+e7yFHbg8oLG8XIfUANODVbsyCyr64= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782885084; c=relaxed/simple; bh=sDSSPuwCpJRo7pBr7CQmXUr8aYCwWORnlCoJeynz2fU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dzJKgMzWju+ceeWC6xPWqapqcl9N58w0vklUjXcTSNZ0JR3Qsr7bQio6iRKaFcJY1OQRkaoaQyNwoaRZ80zCPw30HYgry1ox24jNXC83qK9YaTldKfte5O18EfyNHEqAmWOgyCnr4+po5oHyGKwExgHaySp7DfFr/CNeMC13+ak= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BFbJEcer; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BFbJEcer" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C60D91F000E9; Wed, 1 Jul 2026 05:51:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782885082; bh=Z/Bk6tzCc0Ng60ebNXKHAwFhGzmK1E5JjUoQiZztakc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BFbJEcer+pvCfD4YUpM6qeq3850G1Mf8qSExScerA+W0eWoi6XkmzRrs1MKSikMPN HQ2Vgf9e9NSsfd0JZNbKIGNd1wnyyP/Ms2Y1tLNUCFysjaIWLP+rQt4vtypalBqYYM I0e/MDGxfVD3X+0UOxTf7PJ6hwtX4DSZiiuYzr4G9pZ0DkFmH+21HSoXAqVhgIhr2y zo8uXi2DVCyxNogKLik9E5TcSNrEPJmKHIIo4WpHBUiPmAKszp78s/FAvPQlqjG9BF FKlCxXd9QiM4LWVLynylWeb94+bHhfXl/HMqFn/DV38j2ejGShzAvogtCgSIoHwVZW eATAbo7Q3VnpQ== From: "Aneesh Kumar K.V (Arm)" To: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev Cc: "Aneesh Kumar K.V (Arm)" , Robin Murphy , Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , Mostafa Saleh , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , x86@kernel.org Subject: [PATCH v7 09/22] dma-mapping: Add internal shared allocation attribute Date: Wed, 1 Jul 2026 11:19:13 +0530 Message-ID: <20260701054926.825925-10-aneesh.kumar@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260701054926.825925-1-aneesh.kumar@kernel.org> References: <20260701054926.825925-1-aneesh.kumar@kernel.org> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit DMA_ATTR_CC_SHARED describes an existing DMA mapping whose backing memory is already shared, or decrypted, for confidential computing. It is a mapping attribute: callers use it to request a shared DMA address encoding for memory that has already been prepared for shared DMA. Allocation paths need a related but different state. Once the DMA core decides that an allocation must use shared backing pages, the lower-level allocation helpers need to select shared pools, decrypt newly allocated pages, derive the DMA address with the shared-memory translation and restore encryption on free. That state is internal to the DMA-mapping implementation and should not be passed by drivers to dma_alloc_attrs(). Signed-off-by: Aneesh Kumar K.V (Arm) --- Documentation/core-api/dma-attributes.rst | 29 +++++++++++++++++++++++ include/linux/dma-mapping.h | 8 +++++++ include/trace/events/dma.h | 3 ++- 3 files changed, 39 insertions(+), 1 deletion(-) diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst index 123c8468d58f..eee743184acd 100644 --- a/Documentation/core-api/dma-attributes.rst +++ b/Documentation/core-api/dma-attributes.rst @@ -179,3 +179,32 @@ interface when building their uAPIs, when possible. It must never be used in an in-kernel driver that only works with kernel memory. + +DMA_ATTR_CC_SHARED +------------------ + +This attribute indicates that a DMA mapping is shared, or decrypted, for +confidential computing guests. For normal system memory, the caller must +already have marked the memory decrypted with set_memory_decrypted(). CPU +PTEs for the mapping must use pgprot_decrypted(), and the same shared +semantic may be passed to a vIOMMU when it sets up the IOPTE. + +This attribute describes an existing mapping. It does not allocate shared +backing pages and must not be passed to dma_alloc_attrs(). For MMIO, use +this together with DMA_ATTR_MMIO to indicate shared MMIO. Unless +DMA_ATTR_MMIO is provided, the mapping requires a struct page. + +__DMA_ATTR_ALLOC_CC_SHARED +-------------------------- + +This is an internal DMA-mapping attribute for confidential computing guests. +It is used by allocation paths after the DMA core has determined that the +backing pages must be shared, or decrypted. For example, the direct DMA and +SWIOTLB allocation paths use it to select shared DMA pools, decrypt newly +allocated pages, derive DMA addresses using the shared-memory translation, and +restore encryption on free. + +__DMA_ATTR_ALLOC_CC_SHARED differs from DMA_ATTR_CC_SHARED in that it is not +a caller-visible DMA API attribute. DMA_ATTR_CC_SHARED describes an +already-shared mapping and requires the caller to have prepared normal +system memory before mapping it. diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index cc0823a99cfd..a3e880649fa4 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -103,6 +103,14 @@ */ #define DMA_ATTR_CC_SHARED (1UL << 13) +/* + * __DMA_ATTR_ALLOC_CC_SHARED: Internal DMA-mapping attribute used by + * allocation paths that create shared (decrypted) backing pages for + * confidential computing guests. Drivers must not pass this attribute to + * dma_alloc_attrs(). + */ +#define __DMA_ATTR_ALLOC_CC_SHARED (1UL << 14) + /* * A dma_addr_t can hold any valid DMA or bus address for the platform. It can * be given to a device to use as a DMA source or target. It is specific to a diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h index 31c9ddf72c9d..9df02c1511de 100644 --- a/include/trace/events/dma.h +++ b/include/trace/events/dma.h @@ -35,7 +35,8 @@ TRACE_DEFINE_ENUM(DMA_NONE); { DMA_ATTR_MMIO, "MMIO" }, \ { DMA_ATTR_DEBUGGING_IGNORE_CACHELINES, "CACHELINES_OVERLAP" }, \ { DMA_ATTR_REQUIRE_COHERENT, "REQUIRE_COHERENT" }, \ - { DMA_ATTR_CC_SHARED, "CC_SHARED" }) + { DMA_ATTR_CC_SHARED, "CC_SHARED" }, \ + { __DMA_ATTR_ALLOC_CC_SHARED, "ALLOC_CC_SHARED" }) DECLARE_EVENT_CLASS(dma_map, TP_PROTO(struct device *dev, phys_addr_t phys_addr, dma_addr_t dma_addr, -- 2.43.0