From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f45.google.com (mail-wm1-f45.google.com [209.85.128.45]) (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 CEC42448BBB for ; Tue, 28 Jul 2026 14:26:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785248772; cv=none; b=Zmkf1F3TsnKil2fTQM+uchEPHNuVB0C/2cyaGI/KEt9N5Aiik2ajAWxvG3UMyTpO3dAtvHirVTeeKxy1MxM/aOOvT5nPVxCKLa5Glz/MHpZrq9g8AE/ntf8yelgNoFghyJtxx61tSTAiIfuQl0e1uLiDF7VWvsmhH05hUqEeDfI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785248772; c=relaxed/simple; bh=kcHzJYFXRY1vN3ZEMF3nRLAjfmrJkH7B2gEfA9eBK5w=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PiHLCs+hY6baMztazCA+HCq8lJsc/7yyTPWBr53v42EpnEDYCL1KrTa0QbsIGL49nnQNjX6mLCuEgq2w73z1mT1i2eR2Omzu4GF6yAaIC5PLMP9mBqvhrf8QzxffcU7IyCM02pIdGjibD4NeLmIu4doITmQ+T67f7y1HxFQV5+I= 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=bJhzITze; arc=none smtp.client-ip=209.85.128.45 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="bJhzITze" Received: by mail-wm1-f45.google.com with SMTP id 5b1f17b1804b1-495509b08ebso49355e9.1 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=lists.linux.dev; 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=bJhzITzevdph98qSJCMEbGe8bjdUHRCuXNmmNBwhEgwR0D1nEQ0YA9d1VP+S38Z/de RSC1da3nmVkcJgF2VV1HpwhMCMtoADIq4zB5kGVSuMS4kTxUFPpbwhD0jzdWyBSDByoy /zSan0lwYjOWFGOfmVqyheXbOQ8Y6n3y+r0QZazKNZA1nnGkqY4bp8fh4gUoCZM+Iicw EeEAyDrjwmSnAOZQ+k2fG8dbE05ytgEa0aJu6RFPNM1dkRv2J9HLXPqAY8ef+UGwdUwi YUgXrsaen9UnwbtLt+nQqSYLkMNp05iCbZgyUACwWE6aNoNam0DyJoKEXZ9pjwt0VP1J dElQ== 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=svYfQTrDOU4e7Vv1MR3MrNgpWlSIhRerklFS2yM4vGi8qn0YZfylxK4dTevS/+0NLC oiL07S17cNUAaHKRB4V08Npq+MVvZkL+zyYcz885CSH7UA26bikIFG6w40Z8exvWI9Ux UAZXl1re3Ha7PSl0dbIcV1LGXnQ69b2QO1KpIMpkGAeXDRqUzQb+XgicPE0MC7l+P4OA 3IDfWMOtFy+OQRtaZf8cnHsuY1DTdpcQiQ9TETp887XBYansLwHWBLLMsmI+kY6HA59h Dv4Xjzv/3p7moNkLvaDbogiHljsshW3EoxS4gSqyu7oYZmBleERDpAQ+P3FNXDl2AtA1 D0Jg== X-Forwarded-Encrypted: i=1; AHgh+RpT1ym9V92ohDvNJhqOEo+pLHtKWatBjhsVMkkeYkkROHs39KR5LEofHFM+bgWoVIAv4kGo2ehfS8S4@lists.linux.dev X-Gm-Message-State: AOJu0YwPHz553gX3+KYprClUCGPeW/9Ma+C5B5hIag+DiOe2w3ONSQBE 0D9CHpXvALNQU8kfzON2uRhXhy8yIDZUq6pJqE+IDERDH80YwsV1BmWWYa2NMYCIfA== X-Gm-Gg: AR+sD11ScgvZq7fr5rnUZNZSb94I3jIiL5BCZLqln1fI2DZCNLOdW6tnSKj9I4Vrgvr VMpPAD4VUc8d7FfzngOQNc+7qIuCJHunAnysCRSyZ8SpDuS5vyYl3OYd1OObEXiXwxrdkKhGrc9 t7y3wh/u4/gae5pfOpDFeYMOlV9X+vO3WFDCO1JRegGu58O904Ey7h92MWls/DsTrjBS/N8ROi8 0q7clZYtOGCtpZTCTXXVw2l39NcR1aLnuZsMruo9PtGfdvHeK0TLb9J0on5hQ2xg+XMhrU+lWbr V1M4rmnYDTujHyHKclmerJOfSvfzmkgevZiuHSUji+17JEXVRY3xPOaSwfdBVLfe80kiWhVNobS ghtKyUsf68U/nI/up50PIr1/JZ3rENXTAWNa8dOnKgx+cUBuxf+4bJisjq2C2Ih1i7Y7L5LOiV9 kU93YI4+X4H+7f9d8CePXPzZ0PS6LKO+kMg+8nM4ZZGnY= 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-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: <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 >