From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.marcansoft.com (marcansoft.com [212.63.210.85]) (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 7CA97656; Fri, 22 Sep 2023 14:41:28 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: marcan@marcan.st) by mail.marcansoft.com (Postfix) with ESMTPSA id BF90341EF0; Fri, 22 Sep 2023 14:41:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=marcan.st; s=default; t=1695393686; bh=lDhC+n6ls99EOxSEkF04q5kIJM1xdvRrM1BoHUoxzoE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=lCVyEpNKQCiOkwKuzEN7YClEr0FV8ee6fdpIoePu3wqo/BR8OYcIxVrlzVg4qKhcZ a+GZVHrQlbyWrxHoNQPd/nEn29qcX3iJBl4vFvA94HqjSirm18rNXwsYFEAVRhcYDT lzlioitv43db755lYVTG1TMvqwa1rRMN5TLTSSLVksCdDR7g8xMunzi32UpR6Jl5Hp 7Iu/lHT25QI0iLFzhP0mHpIpQslyQ9XmmV8lobjqgeefXihivo7DMhZ/n1Zvqo9s9f XDIDcnV0k4wwslzsNRxZZHN0Fyjqm2JB7aOazFhacD+/2Ue5fOdmrqDodqzCjxtJFJ kHmXoAW0zU1vw== Message-ID: Date: Fri, 22 Sep 2023 23:41:17 +0900 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH REGRESSION] iommu: Only allocate FQ domains for IOMMUs that support them To: Robin Murphy , Joerg Roedel , Will Deacon , Jason Gunthorpe , Jerry Snitselaar Cc: Joerg Roedel , Neal Gompa , "Justin M. Forbes" , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, asahi@lists.linux.dev, stable@vger.kernel.org, regressions@lists.linux.dev References: <20230922-iommu-type-regression-v1-1-1ed3825b2c38@marcan.st> <2ea199a1-d20d-2fde-d1bd-76ecad14a68d@arm.com> Content-Language: en-US From: Hector Martin In-Reply-To: <2ea199a1-d20d-2fde-d1bd-76ecad14a68d@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 22/09/2023 23.21, Robin Murphy wrote: > On 22/09/2023 2:40 pm, Hector Martin wrote: >> Commit a4fdd9762272 ("iommu: Use flush queue capability") hid the >> IOMMU_DOMAIN_DMA_FQ domain type from domain allocation. A check was >> introduced in iommu_dma_init_domain() to fall back if not supported, but >> this check runs too late: by that point, devices have been attached to >> the IOMMU, and the IOMMU driver might not expect FQ domains at >> ops->attach_dev() time. >> >> Ensure that we immediately clamp FQ domains to plain DMA if not >> supported by the driver at device attach time, not later. >> >> This regressed apple-dart in v6.5. > > Apologies, I missed that apple-dart was doing something unusual here. > However, could we just fix that directly instead? > > diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c > index 2082081402d3..0b8927508427 100644 > --- a/drivers/iommu/apple-dart.c > +++ b/drivers/iommu/apple-dart.c > @@ -671,8 +671,7 @@ static int apple_dart_attach_dev(struct iommu_domain > *domain, > return ret; > > switch (domain->type) { > - case IOMMU_DOMAIN_DMA: > - case IOMMU_DOMAIN_UNMANAGED: > + default: > ret = apple_dart_domain_add_streams(dart_domain, cfg); > if (ret) > return ret; > > > That's pretty much where we're headed with the domain_alloc_paging > redesign anyway - at the driver level, operations on a paging domain > should not need to know about the higher-level usage intent of that > domain. Ideally, blocking and identity domains should have their own > distinct ops now as well, but that might be a bit too big a change for > an immediate fix here. Sure, but it sounded like if there's a capability for this the core should probably use it and not expose the type at all to drivers that can't support it :) If you think defaulting to that branch in DART is correctly future-proof I can make that change. It's not the only driver checking the domain type in attach_dev(), but it might be the only one enumerating all the options instead of checking for specific cases only (e.g. intel checks for IOMMU_DOMAIN_IDENTITY). - Hector