From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f47.google.com (mail-wm1-f47.google.com [209.85.128.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB483448B98 for ; Tue, 28 Jul 2026 14:26:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785248773; cv=none; b=n/eFa7esweR3LVBSnJEzjXuhBqx+ltuGqHJEQmciff5fOvKVOt++Zwq1XT2yjKN1CiAUfk6qC/ioKDsMjOapxbrJv+FK7+o1fRXimZALiCZzmCqdoqo7GjDjLUrlSbjUDI9olEs4i3/01sqq4ooF3KdtXU/borkqAsrWeKzp5fc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785248773; c=relaxed/simple; bh=kcHzJYFXRY1vN3ZEMF3nRLAjfmrJkH7B2gEfA9eBK5w=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HZIh8tEeUxHBOnRVHN7bJAYEOlJ0FcA5xMPcCXrgNFQAN5v86FxtLLLZHKLsB/Ni/KeifrgymHaIni788UfmSa3kRvfl4TKu1OQKFdcEEwjcSw5A1aACzH0krR2H+NqF092JJQxF/tDbwjdcVWv6DSHhRtnzDLq/aPlIXPb9RqE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=QjSO98bL; arc=none smtp.client-ip=209.85.128.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QjSO98bL" Received: by mail-wm1-f47.google.com with SMTP id 5b1f17b1804b1-493be0fbcc5so62195e9.0 for ; Tue, 28 Jul 2026 07:26:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1785248769; x=1785853569; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=vpWtv0pYfxndfeslGolf2QwgOrAZhpu3GPmCVKvsSLo=; b=QjSO98bLksvvZrbfytJYxgzpvAFD8fmWkFFix+UqpmJ35UPu+n9wLMT0WChn5UxO91 5wUiDVHhevzDxhiOu/zs7axqpQEuvHWlXf5+m1i8yDcj+Vu7zQt26RqpjzSNuub4QMjf zOs2woHWaORnl4Ky6AsNyhLKNOodM2dHTu7zxc0CtLmzRtuEMw7Wp+otfv6PCY3OBTIw SyXEZE345/UkqQlvhqg+FN1p4EhLjcsPQXm3Iql8cUG0tJDLCOASoKYclJbtX/PU/yiu lts6PJMoe/8r+xBfKX/hgXCYv5ltdPBEDUtQFhDCVSbhnlmgQpS5iAu3ek5wbtdHsgAe Esug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785248769; x=1785853569; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=vpWtv0pYfxndfeslGolf2QwgOrAZhpu3GPmCVKvsSLo=; b=kYvvq5OCvtKIA6HfziWirZy3pHZl/XzTAIc1n4YNVd7D+9NJNe9zEP5MEuY48fK11G lfcWAzM48UoyKlNTnvCOWpSopqgBTYzyu2RwOujIlbP6hkRzcpbRS2FqDS1lr6KXS7s9 3mEiWITdQyt1sumpadg8CXSLgtXyMqlPzfNLM/yJqsjbOBV9wdqgGMstVSP1QbfsddQg ruAmOhAR74dxM+JR+tD0KODQPfxqJzVAfhKeZE8Tf7SEm2sSSa8TwlcImervELDf1vBT oUlCIpgrslmjhBfwFCUhwmGf37sNuQOnLwmy3vCnwFzCYuOwPTuL9EsG2XxMNgj8WPAI Xu5Q== X-Forwarded-Encrypted: i=1; AHgh+RqYZfzMgW5CohYulPsYiPcQXEjAt3K32RrAYzh3ozI85Pr/hTDEuLHmbnHM+TY0nblnaBHOHBWaoRE2@vger.kernel.org X-Gm-Message-State: AOJu0YwWR1yGbwU0i0mqLVV2cD0NxUsB4DTOTIUTR3n2qtyqVDKxV1lT 2F2L4j+i1qO36bOKH+PbKNGdChmRCUEx10sqaLTPPymmvLEjC030K0WSSS40owNDFw== X-Gm-Gg: AR+sD10lIgayrhVLHIoVNaETAoNjIRLROIVCwQitKRGHlRuHAFQxYPl9Q2zTU0LQYPN kZcZVvcXNqi0v/T/n9qw6Tc1bAB1vDWCmT/08CXl1Rzw9sSIdi4ylg9XzhUOhNy4pKtEZ0JCYH4 zX4yPk3zgVhucwQZKSWic7nvWtjvpjNHMOF71BmZi8CA7GiMWYDyWrXla1EJGv3gNvTAccVTa8I /tLBKBwRRDsZ0D1sP5V36Ez2c79CrK6fxm7HVkAGZGGaZWZSV3cdqgjkzTVaGSt4fdfUY/nk8DO 7KCYU2X/z177AYYPb1CmD/0QqDTpFYz+tZ8Udo7yd24HEsf8ryUbk0m5HDLXj4dnzPW8dBUSTRP yV7grcG1/m9omFfuH2nGOn2aMUgGFRY4cenH1p2jccQL2NEV8zXpSSp/1Q4O5+jNgHySQhUGWL4 WbcVEwI1k9lQyJAOpODMOTiIUI8rTnAgrzOFeQ22PpUIs= X-Received: by 2002:a05:600c:4583:b0:493:aca0:32e2 with SMTP id 5b1f17b1804b1-496b4cf6c38mr21115e9.4.1785248768109; Tue, 28 Jul 2026 07:26:08 -0700 (PDT) Received: from google.com (250.192.189.35.bc.googleusercontent.com. [35.189.192.250]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47f85bb57cfsm60556481f8f.11.2026.07.28.07.26.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 07:26:07 -0700 (PDT) Date: Tue, 28 Jul 2026 14:25:58 +0000 From: Mostafa Saleh To: "Aneesh Kumar K.V (Arm)" Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Robin Murphy , Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , 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, Jason Gunthorpe Subject: Re: [PATCH v8 09/23] dma-mapping: Add internal shared allocation attribute Message-ID: References: <20260717180442.110954-1-aneesh.kumar@kernel.org> <20260717180442.110954-10-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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260717180442.110954-10-aneesh.kumar@kernel.org> On Fri, Jul 17, 2026 at 11:34:27PM +0530, Aneesh Kumar K.V (Arm) wrote: > 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(). > > Reviewed-by: Jason Gunthorpe > Signed-off-by: Aneesh Kumar K.V (Arm) Reviewed-by: Mostafa Saleh Thanks, Mostafa > --- > 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 >