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Wed, 17 Jun 2026 14:46:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781707613; bh=erXy90F1aVhSTW8POQ0NgCMddX+dCML396UHDEIaezg=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=laR53S4ZEFqpK1RU2C/yjKgmXtvMoVq6Ik55ii1gAWmh3rRuIBk1UrsjhJal8Mf7Y nKNxtvFmqU30GaFlFd6gJbCL6OuI9sKlymNooPjqVLA22wKu2cf7YHqk3iUzTcFnOg AonnWRxxacImdlprsatSccr+it2PVoCE2farsGQZ0BWMkTXGQH9HozuVaFKisG7AwT 5FkwBoRfJFlzW7mX9CM093Zy2Sxh6cGHKqN/0EWAVZkIvKHcMUePMuRTEjPFcC8cMu msrJ3x9CnBMTnDsAFfGnXCnBCSM+Po6oFWp3nnIuybjDCDIkSmxHIeOL5R+Ez/oZG3 ThZCeuyOnZbdQ== X-Mailer: emacs 30.2 (via feedmail 11-beta-1 I) From: Aneesh Kumar K.V To: Alexey Kardashevskiy , iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev Cc: Robin Murphy , Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , Mostafa Saleh , Petr Tesarik , 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, Jiri Pirko , Michael Kelley , "Cheloha, Scott" Subject: Re: [PATCH v6 03/20] dma-direct: use DMA_ATTR_CC_SHARED in alloc/free paths In-Reply-To: <845d0c8a-6d51-47aa-8e0b-8381e733444a@amd.com> References: <20260604083959.1265923-1-aneesh.kumar@kernel.org> <20260604083959.1265923-4-aneesh.kumar@kernel.org> <845d0c8a-6d51-47aa-8e0b-8381e733444a@amd.com> Date: Wed, 17 Jun 2026 15:46:41 +0100 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 Alexey Kardashevskiy writes: > On 4/6/26 18:39, 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. >> >> This updates dma_direct_alloc(), dma_direct_free(), and >> dma_direct_alloc_pages() to fold the forced unencrypted case into attrs. >> >> Tested-by: Jiri Pirko >> Tested-by: Michael Kelley >> Tested-by: Mostafa Saleh >> Signed-off-by: Aneesh Kumar K.V (Arm) >> --- >> kernel/dma/direct.c | 53 +++++++++++++++++++++++++++++++++++++-------- >> 1 file changed, 44 insertions(+), 9 deletions(-) >> >> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c >> index a741c8a2ee66..90dc5057a0c0 100644 >> --- a/kernel/dma/direct.c >> +++ b/kernel/dma/direct.c >> @@ -193,16 +193,31 @@ void *dma_direct_alloc(struct device *dev, size_t size, >> dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs) >> { >> bool remap = false, set_uncached = false; >> - bool mark_mem_decrypt = true; >> + bool mark_mem_decrypt = false; >> struct page *page; >> void *ret; >> >> + /* >> + * 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. > > Why this limit? > > Context: I am looking for a memory pool for a few shared pages (to do > some guest<->host communication), SWIOTLB seems like the right fit but > swiotlb_alloc() is not exported and > dma_direct_alloc(DMA_ATTR_CC_SHARED) is not allowed. Thanks, > swiotlb is not the right pool to use for that, right? CCA had a similar requirement for ITS pages and ended up creating a genpool: b08e2f42e86b ("irqchip/gic-v3-its: Share ITS tables with a non-trusted hypervisor") -aneesh