From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 909FD2BEC55; Wed, 22 Apr 2026 05:50:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776837035; cv=none; b=I4Ys907DY3B4FBhQ039UgR8H8Mgn/AAQxC9Qicxs6au/D9lmauaalH4KQjtVLfP9q0C73lwrgEUf8hL7OXk20xa70/zaxsHWB9+a7m8fVaA9PN6T1yc3DxpxLzwLz3icMBm7xx3N2W38cvHVK4z4XYApXgmPfheuxAwPLFcQ3jE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776837035; c=relaxed/simple; bh=9G2hh9Uof2dUVKFnd6uvXoI4j0yPeySOhLTI5bmV91A=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=tg0tvgvE581d8GoEKgAGCF594R5ZpPB5V8rSlqq8PfQhqnvxoHm8igQXitInnY7mcOWkA9uySfIi/9TiLlslfe7zyeQ8DLJVgp5fkWQ/UPZXAZZwvALyxZcJMbUIsHmxD5je03r0jwospzG6zEaG72sjm1oBd2i6ZJ3lPpTwoFE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=moca9Eld; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="moca9Eld" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E4D28C19425; Wed, 22 Apr 2026 05:50:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776837035; bh=9G2hh9Uof2dUVKFnd6uvXoI4j0yPeySOhLTI5bmV91A=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=moca9Eldi4xx6PpPgoxHAXzboDoaDwcGgRMVsouSd4PTVra9mScNpzRWWMzKNkp5V MSoepPt9GQmISmnOvFX3jZlkzJ4WfNXJ/GLUpSy13h58rm1qvROotFD6lhahYDoAGZ IeHR7w7oDd6y3eBStpCNcw95y1Y4NQ54B+fPdPQ46knfFA+IolFthX7t5Fh/LuoTYR 07BRvumoDzmYXBxk3zWlsNIuWTGVJM49C/mHUQvcNup1YkNWveQuA1IN0dovD1Daka 3MocKv3WoGyOX9kPRqJaTHibVAjIVABVggZpGVyFLdfu6MU/LSZmOvMUhJCGcR8RqW 7Yqm398eXNpjg== X-Mailer: emacs 30.2 (via feedmail 11-beta-1 I) From: Aneesh Kumar K.V To: Jason Gunthorpe Cc: iommu@lists.linux.dev, linux-kernel@vger.kernel.org, robin.murphy@arm.com, m.szyprowski@samsung.com, will@kernel.org, maz@kernel.org, suzuki.poulose@arm.com, catalin.marinas@arm.com, jiri@resnulli.us, Mostafa Saleh Subject: Re: [PATCH v2 6/8] dma-direct: make dma_direct_map_phys() honor DMA_ATTR_CC_SHARED In-Reply-To: <20260421122924.GB3611611@ziepe.ca> References: <20260420061415.3650870-1-aneesh.kumar@kernel.org> <20260420061415.3650870-7-aneesh.kumar@kernel.org> <20260421122924.GB3611611@ziepe.ca> Date: Wed, 22 Apr 2026 11:20:28 +0530 Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Jason Gunthorpe writes: > On Mon, Apr 20, 2026 at 11:44:13AM +0530, Aneesh Kumar K.V (Arm) wrote: >> Teach dma_direct_map_phys() to select the DMA address encoding based on >> DMA_ATTR_CC_SHARED. >> >> Use phys_to_dma_unencrypted() for decrypted mappings and >> phys_to_dma_encrypted() otherwise. If a device requires unencrypted DMA >> but the source physical address is still encrypted, force the mapping >> through swiotlb so the DMA address and backing memory attributes remain >> consistent. >> >> Signed-off-by: Aneesh Kumar K.V (Arm) >> --- >> kernel/dma/direct.h | 25 ++++++++++++++----------- >> 1 file changed, 14 insertions(+), 11 deletions(-) >> >> diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h >> index 7140c208c123..928671ef01e9 100644 >> --- a/kernel/dma/direct.h >> +++ b/kernel/dma/direct.h >> @@ -86,9 +86,14 @@ static inline dma_addr_t dma_direct_map_phys(struct device *dev, >> phys_addr_t phys, size_t size, enum dma_data_direction dir, >> unsigned long attrs, bool flush) >> { >> + bool force_swiotlb_map = false; >> dma_addr_t dma_addr; >> >> - if (is_swiotlb_force_bounce(dev)) { >> + /* if phys addr attribute is encrypted but the device is forcing an encrypted dma addr */ >> + if (!(attrs & DMA_ATTR_CC_SHARED) && force_dma_unencrypted(dev)) >> + force_swiotlb_map = true; > > continuing my prior email.. This is really in the wrong spot, it > should be in dma_capable() > >> + if (is_swiotlb_force_bounce(dev) || force_swiotlb_map) { >> if (!(attrs & DMA_ATTR_CC_SHARED)) { >> if (attrs & (DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT)) >> return DMA_MAPPING_ERROR; >> @@ -105,18 +110,16 @@ static inline dma_addr_t dma_direct_map_phys(struct device *dev, >> goto err_overflow; >> } else if (attrs & DMA_ATTR_CC_SHARED) { >> dma_addr = phys_to_dma_unencrypted(dev, phys); >> - if (unlikely(!dma_capable(dev, dma_addr, size, false))) >> - goto err_overflow; >> } else { >> - dma_addr = phys_to_dma(dev, phys); >> - if (unlikely(!dma_capable(dev, dma_addr, size, true)) || >> - dma_kmalloc_needs_bounce(dev, size, dir)) { > > here. > > swiotlb because the device can't reach a high address and swiotlb > because the device doesn't have T=1 are really the same thing and > should have the same code flow. > > Add attrs to dma_capable() and check force_dma_unencrypted(dev) > inside. > will update in the next revision > >> - if (is_swiotlb_active(dev) && >> - !(attrs & DMA_ATTR_REQUIRE_COHERENT)) >> - return swiotlb_map(dev, phys, size, dir, attrs); >> + dma_addr = phys_to_dma_encrypted(dev, phys); >> + } >> >> - goto err_overflow; >> - } >> + if (unlikely(!dma_capable(dev, dma_addr, size, true)) || >> + dma_kmalloc_needs_bounce(dev, size, dir)) { >> + if (is_swiotlb_active(dev) && >> + !(attrs & DMA_ATTR_REQUIRE_COHERENT)) >> + return swiotlb_map(dev, phys, size, dir, attrs); >> + goto err_overflow; >> } > > Then this movement shouldn't be needed? I am still not clear about the use of DMA_ATTR_CC_SHARED here. If the resulting DMA address is not dma_capable, I was expecting that we should fall back to swiotlb_map(). That was the intention behind this change. However, the other email thread suggests that DMA_ATTR_CC_SHARED is always used with swiotlb_force_bounce(). I think we should address that. If we do, the goal here would be to check dma_capable for both shared and private addresses. For private/protected addresses, swiotlb_map() will currently fail with DMA_MAPPING_ERROR because the default io_tlb_mem (dev->dma_io_tlb_mem) is decrypted by default -aneesh