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Thu, 14 May 2026 05:01:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6A5FC2BCB7; Thu, 14 May 2026 05:01:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778734904; bh=1MkgikfobnnlXszu7oxK5om44m9zNem1u1FAvwxDkPc=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=o/TU8m9rl7cjkl/2skOf7z8JNyS5pEEj1mPV4RtgOnPRWyJpSYblQYNiNFDTeFVk8 gU4giYSM4safXp6KaQXjocZhyTtJ4S0lFTopjislANRrONcrvJeo5n+BW0SlTMu/9y BCHG7SXjUd4yMTWX4t8i+xiIiCrVanPCZHefstfatgj26vxkH3G8OnCJLztrLsLWdp zvoCVCUtEa+qGVjmY8fB703D6M0ojTio/PP2PkUqJBAmF+sEtE+n+dNxKLidPSaEHE jMfzrjVvUX0JNhAbNLWyCF4+/393zwZ2HvF1SPftZF04LcdJklp/gXVEnoRSBtSGkQ NkNLmRpeIccsA== X-Mailer: emacs 30.2 (via feedmail 11-beta-1 I) From: Aneesh Kumar K.V To: Mostafa Saleh 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 Subject: Re: [PATCH v4 02/13] dma-direct: use DMA_ATTR_CC_SHARED in alloc/free paths In-Reply-To: References: <20260512090408.794195-1-aneesh.kumar@kernel.org> <20260512090408.794195-3-aneesh.kumar@kernel.org> Date: Thu, 14 May 2026 10:31:30 +0530 Message-ID: X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Mostafa Saleh writes: > On Tue, May 12, 2026 at 02:33:57PM +0530, Aneesh Kumar K.V (Arm) wrote: >> Propagate force_dma_unencrypted() into DMA_ATTR_CC_SHARED in the >> dma-direct allocation path and use the attribute to drive the related >> decisions. >>=20 >> This updates dma_direct_alloc(), dma_direct_free(), and >> dma_direct_alloc_pages() to fold the forced unencrypted case into attrs. >>=20 >> Signed-off-by: Aneesh Kumar K.V (Arm) >> --- >> kernel/dma/direct.c | 44 ++++++++++++++++++++++++++++++++++++-------- >> 1 file changed, 36 insertions(+), 8 deletions(-) >>=20 >> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c >> index b958f150718a..0c2e1f8436ce 100644 >> --- a/kernel/dma/direct.c >> +++ b/kernel/dma/direct.c >> @@ -201,16 +201,31 @@ void *dma_direct_alloc(struct device *dev, size_t = size, >> dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs) >> { >> bool remap =3D false, set_uncached =3D false; >> - bool mark_mem_decrypt =3D true; >> + bool mark_mem_decrypt =3D false; >> struct page *page; >> void *ret; >>=20=20 >> + /* >> + * DMA_ATTR_CC_SHARED is not a caller-visible dma_alloc_*() >> + * attribute. The direct allocator uses it internally after it has >> + * decided that the backing pages must be shared/decrypted, so the >> + * rest of the allocation path can consistently select DMA addresses, >> + * choose compatible pools and restore encryption on free. >> + */ >> + if (attrs & DMA_ATTR_CC_SHARED) >> + return NULL; >> + >> + if (force_dma_unencrypted(dev)) { >> + attrs |=3D DMA_ATTR_CC_SHARED; >> + mark_mem_decrypt =3D true; >> + } >> + >> size =3D PAGE_ALIGN(size); >> if (attrs & DMA_ATTR_NO_WARN) >> gfp |=3D __GFP_NOWARN; >>=20=20 >> - if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) && >> - !force_dma_unencrypted(dev) && !is_swiotlb_for_alloc(dev)) >> + if (((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | DMA_ATTR_CC_SHARED)) =3D=3D >> + DMA_ATTR_NO_KERNEL_MAPPING) && !is_swiotlb_for_alloc(dev)) >> return dma_direct_alloc_no_mapping(dev, size, dma_handle, gfp); >>=20=20 >> if (!dev_is_dma_coherent(dev)) { >> @@ -244,7 +259,7 @@ void *dma_direct_alloc(struct device *dev, size_t si= ze, >> * Remapping or decrypting memory may block, allocate the memory from >> * the atomic pools instead if we aren't allowed block. >> */ >> - if ((remap || force_dma_unencrypted(dev)) && >> + if ((remap || (attrs & DMA_ATTR_CC_SHARED)) && >> dma_direct_use_pool(dev, gfp)) >> return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); >>=20=20 >> @@ -318,11 +333,20 @@ void *dma_direct_alloc(struct device *dev, size_t = size, >> void dma_direct_free(struct device *dev, size_t size, >> void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs) >> { >> - bool mark_mem_encrypted =3D true; >> + bool mark_mem_encrypted =3D false; >> unsigned int page_order =3D get_order(size); >>=20=20 >> - if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) && >> - !force_dma_unencrypted(dev) && !is_swiotlb_for_alloc(dev)) { >> + /* >> + * if the device had requested for an unencrypted buffer, >> + * convert it to encrypted on free >> + */ >> + if (force_dma_unencrypted(dev)) { >> + attrs |=3D DMA_ATTR_CC_SHARED; >> + mark_mem_encrypted =3D true; >> + } >> + >> + if (((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | DMA_ATTR_CC_SHARED)) =3D=3D >> + DMA_ATTR_NO_KERNEL_MAPPING) && !is_swiotlb_for_alloc(dev)) { >> /* cpu_addr is a struct page cookie, not a kernel address */ >> dma_free_contiguous(dev, cpu_addr, size); >> return; >> @@ -365,10 +389,14 @@ void dma_direct_free(struct device *dev, size_t si= ze, >> struct page *dma_direct_alloc_pages(struct device *dev, size_t size, >> dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp) >> { >> + unsigned long attrs =3D 0; >> struct page *page; >> void *ret; >>=20=20 >> - if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp)) >> + if (force_dma_unencrypted(dev)) >> + attrs |=3D DMA_ATTR_CC_SHARED; >> + >> + if ((attrs & DMA_ATTR_CC_SHARED) && dma_direct_use_pool(dev, gfp)) >> return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); > > What about dma_direct_free_pages()? Nothing inside uses attrs, but > that=E2=80=99s quite similar to dma_direct_alloc_pages() > > Also, at this point, shouldn=E2=80=99t this patch also remove > force_dma_unencrypted() calls from dma_set_decrypted() and > dma_set_encrypted()? > The final change have=20 void dma_direct_free_pages(struct device *dev, size_t size, ... { /* * if the device had requested for an unencrypted buffer, * convert it to encrypted on free */ bool mark_mem_encrypted =3D force_dma_unencrypted(dev); That got added by "dma-direct: select DMA address encoding from DMA_ATTR_CC= _SHARED " I'll move that hunk into this patch. The overall goal is=20 dma_direct_alloc(.. attrs) { if (force_dma_unencrypted(dev)) attrs |=3D DMA_ATTR_CC_SHARED; } dma_direct_free(.. attrs) { if (force_dma_unencrypted(dev)) { attrs |=3D DMA_ATTR_CC_SHARED; mark_mem_encrypted =3D true; } if (swiotlb_find_pool(dev, dma_to_phys(dev, dma_addr))) mark_mem_encrypted =3D false; } dma_direct_alloc_pages() { if (force_dma_unencrypted(dev)) attrs |=3D DMA_ATTR_CC_SHARED; } dma_direct_free_pages() { bool mark_mem_encrypted =3D force_dma_unencrypted(dev); if (swiotlb_find_pool(dev, page_to_phys(page))) mark_mem_encrypted =3D false; } -aneesh