From: Christoph Hellwig <hch@lst.de>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: alan.cox@intel.com, Christoph Hellwig <hch@lst.de>,
Stefano Stabellini <sstabellini@kernel.org>,
ashok.raj@intel.com, Jonathan Corbet <corbet@lwn.net>,
pengfei.xu@intel.com, Ingo Molnar <mingo@redhat.com>,
David Woodhouse <dwmw2@infradead.org>,
kevin.tian@intel.com,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Steven Rostedt <rostedt@goodmis.org>,
Bjorn Helgaas <bhelgaas@google.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
mika.westerberg@linux.intel.com, Juergen Gross <jgross@suse.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
jacob.jun.pan@intel.com, Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v5 02/10] iommu/vt-d: Use per-device dma_ops
Date: Thu, 14 Nov 2019 09:14:23 +0100 [thread overview]
Message-ID: <20191114081423.GA27407@lst.de> (raw)
In-Reply-To: <0ddc8aff-783a-97b9-f5cc-9e27990de278@linux.intel.com>
On Thu, Nov 14, 2019 at 01:14:11PM +0800, Lu Baolu wrote:
> Could you please educate me what dma_supported() is exactly for? Will
> it always get called during boot? When will it be called?
->dma_supported is set when setting either the dma_mask or
dma_coherent_mask. These days it serves too primary purposes: reject
too small masks that can't be addressed, and provide any hooks needed
in the driver based on the mask.
> In above implementation, why do we need to check dma_direct_supported()
> at the beginning? And why
Because the existing driver called dma_direct_supported, which I added
based on x86 arch overrides doings the same a while ago. I suspect
it is related to addressing for tiny dma masks, but I'm not entirely
sure. The longer term intel-iommu maintainers or x86 maintainers might
be able to shed more light how this was supposed to work and/or how
systems with the Intel IOMMU deal with e.g. ISA devices with 24-bit
addressing.
>
> if (!info || info == DUMMY_DEVICE_DOMAIN_INFO ||
> info == DEFER_DEVICE_DOMAIN_INFO) {
> dev->dma_ops_bypass = true;
This was supposed to transform the checks from iommu_dummy and
identity_mapping. But I think it actually isn't entirely correct and
already went bad in the patch to remove identity_mapping. Pleae check
the branch I just re-pushed, which should be correct now.
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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Christoph Hellwig <hch@lst.de>,
David Woodhouse <dwmw2@infradead.org>,
Joerg Roedel <joro@8bytes.org>,
Bjorn Helgaas <bhelgaas@google.com>,
ashok.raj@intel.com, jacob.jun.pan@intel.com, alan.cox@intel.com,
kevin.tian@intel.com, mika.westerberg@linux.intel.com,
Ingo Molnar <mingo@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
pengfei.xu@intel.com,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Jonathan Corbet <corbet@lwn.net>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
Jacob Pan <jacob.jun.pan@linux.intel.com>
Subject: Re: [PATCH v5 02/10] iommu/vt-d: Use per-device dma_ops
Date: Thu, 14 Nov 2019 09:14:23 +0100 [thread overview]
Message-ID: <20191114081423.GA27407@lst.de> (raw)
In-Reply-To: <0ddc8aff-783a-97b9-f5cc-9e27990de278@linux.intel.com>
On Thu, Nov 14, 2019 at 01:14:11PM +0800, Lu Baolu wrote:
> Could you please educate me what dma_supported() is exactly for? Will
> it always get called during boot? When will it be called?
->dma_supported is set when setting either the dma_mask or
dma_coherent_mask. These days it serves too primary purposes: reject
too small masks that can't be addressed, and provide any hooks needed
in the driver based on the mask.
> In above implementation, why do we need to check dma_direct_supported()
> at the beginning? And why
Because the existing driver called dma_direct_supported, which I added
based on x86 arch overrides doings the same a while ago. I suspect
it is related to addressing for tiny dma masks, but I'm not entirely
sure. The longer term intel-iommu maintainers or x86 maintainers might
be able to shed more light how this was supposed to work and/or how
systems with the Intel IOMMU deal with e.g. ISA devices with 24-bit
addressing.
>
> if (!info || info == DUMMY_DEVICE_DOMAIN_INFO ||
> info == DEFER_DEVICE_DOMAIN_INFO) {
> dev->dma_ops_bypass = true;
This was supposed to transform the checks from iommu_dummy and
identity_mapping. But I think it actually isn't entirely correct and
already went bad in the patch to remove identity_mapping. Pleae check
the branch I just re-pushed, which should be correct now.
next prev parent reply other threads:[~2019-11-14 8:14 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-25 3:17 [PATCH v5 00/10] iommu: Bounce page for untrusted devices Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 3:17 ` [PATCH v5 01/10] iommu/vt-d: Don't switch off swiotlb if use direct dma Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 5:41 ` Christoph Hellwig
2019-07-25 5:41 ` Christoph Hellwig
2019-07-25 3:17 ` [PATCH v5 02/10] iommu/vt-d: Use per-device dma_ops Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 5:44 ` Christoph Hellwig
2019-07-25 5:44 ` Christoph Hellwig
2019-07-25 7:18 ` Lu Baolu
2019-07-25 7:18 ` Lu Baolu
2019-07-25 11:43 ` Christoph Hellwig
2019-07-25 11:43 ` Christoph Hellwig
2019-07-26 1:56 ` Lu Baolu
2019-07-26 1:56 ` Lu Baolu
2019-11-12 7:16 ` Christoph Hellwig
2019-11-12 7:16 ` Christoph Hellwig
2019-11-13 2:50 ` Lu Baolu
2019-11-13 2:50 ` Lu Baolu
2019-11-13 7:03 ` Christoph Hellwig
2019-11-13 7:03 ` Christoph Hellwig
2019-11-13 9:53 ` Christoph Hellwig
2019-11-13 9:53 ` Christoph Hellwig
2019-11-14 5:14 ` Lu Baolu
2019-11-14 5:14 ` Lu Baolu
2019-11-14 8:14 ` Christoph Hellwig [this message]
2019-11-14 8:14 ` Christoph Hellwig
2019-11-15 0:57 ` Lu Baolu
2019-11-20 10:44 ` Christoph Hellwig
2019-07-25 3:17 ` [PATCH v5 03/10] iommu/vt-d: Cleanup after use per-device dma ops Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 3:17 ` [PATCH v5 04/10] PCI: Add dev_is_untrusted helper Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 5:44 ` Christoph Hellwig
2019-07-25 5:44 ` Christoph Hellwig
2019-07-25 3:17 ` [PATCH v5 05/10] swiotlb: Split size parameter to map/unmap APIs Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 11:47 ` Christoph Hellwig
2019-07-25 11:47 ` Christoph Hellwig
2019-07-25 3:17 ` [PATCH v5 06/10] swiotlb: Zero out bounce buffer for untrusted device Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 11:49 ` Christoph Hellwig
2019-07-25 11:49 ` Christoph Hellwig
2019-07-26 2:21 ` Lu Baolu
2019-07-26 2:21 ` Lu Baolu
2019-07-25 3:17 ` [PATCH v5 07/10] iommu: Add bounce page APIs Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 3:17 ` [PATCH v5 08/10] iommu/vt-d: Check whether device requires bounce buffer Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 3:17 ` [PATCH v5 09/10] iommu/vt-d: Add trace events for device dma map/unmap Lu Baolu
2019-07-25 3:17 ` Lu Baolu
2019-07-25 12:26 ` Steven Rostedt
2019-07-25 12:26 ` Steven Rostedt
2019-07-26 2:24 ` Lu Baolu
2019-07-26 2:24 ` Lu Baolu
2019-07-25 3:17 ` [PATCH v5 10/10] iommu/vt-d: Use bounce buffer for untrusted devices Lu Baolu
2019-07-25 3:17 ` Lu Baolu
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