From: Robin Murphy <robin.murphy@arm.com>
To: Lu Baolu <baolu.lu@linux.intel.com>,
Joerg Roedel <joro@8bytes.org>, Tom Murphy <murphyt7@tcd.ie>,
David Woodhouse <dwmw2@infradead.org>,
Christoph Hellwig <hch@infradead.org>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
Intel-gfx@lists.freedesktop.org, Ashok Raj <ashok.raj@intel.com>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 4/7] iommu: Add quirk for Intel graphic devices in map_sg
Date: Tue, 3 Nov 2020 12:00:33 +0000 [thread overview]
Message-ID: <281f22ed-8b36-fc20-4b08-27ef168f941d@arm.com> (raw)
In-Reply-To: <20200927063437.13988-5-baolu.lu@linux.intel.com>
On 2020-09-27 07:34, Lu Baolu wrote:
> Combining the sg segments exposes a bug in the Intel i915 driver which
> causes visual artifacts and the screen to freeze. This is most likely
> because of how the i915 handles the returned list. It probably doesn't
> respect the returned value specifying the number of elements in the list
> and instead depends on the previous behaviour of the Intel iommu driver
> which would return the same number of elements in the output list as in
> the input list.
>
> Signed-off-by: Tom Murphy <murphyt7@tcd.ie>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> drivers/iommu/dma-iommu.c | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 3526db774611..e7e4d758f51a 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -879,6 +879,33 @@ static int __finalise_sg(struct device *dev, struct scatterlist *sg, int nents,
> unsigned int cur_len = 0, max_len = dma_get_max_seg_size(dev);
> int i, count = 0;
>
> + /*
> + * The Intel graphic driver is used to assume that the returned
> + * sg list is not combound. This blocks the efforts of converting
> + * Intel IOMMU driver to dma-iommu api's. Add this quirk to make the
> + * device driver work and should be removed once it's fixed in i915
> + * driver.
> + */
> + if (IS_ENABLED(CONFIG_DRM_I915) && dev_is_pci(dev) &&
> + to_pci_dev(dev)->vendor == PCI_VENDOR_ID_INTEL &&
> + (to_pci_dev(dev)->class >> 16) == PCI_BASE_CLASS_DISPLAY) {
> + for_each_sg(sg, s, nents, i) {
> + unsigned int s_iova_off = sg_dma_address(s);
> + unsigned int s_length = sg_dma_len(s);
> + unsigned int s_iova_len = s->length;
> +
> + s->offset += s_iova_off;
> + s->length = s_length;
> + sg_dma_address(s) = dma_addr + s_iova_off;
> + sg_dma_len(s) = s_length;
> + dma_addr += s_iova_len;
> +
> + pr_info_once("sg combining disabled due to i915 driver\n");
> + }
> +
> + return nents;
> + }
BTW, a much less invasive workaround would be to simply override
seg_mask to 0. That's enough to make sure that no segment looks eligible
for merging.
Robin.
> +
> for_each_sg(sg, s, nents, i) {
> /* Restore this segment's original unaligned fields first */
> unsigned int s_iova_off = sg_dma_address(s);
>
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next prev parent reply other threads:[~2020-11-03 12:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-27 6:34 [PATCH v4 0/7] Convert the intel iommu driver to the dma-iommu api Lu Baolu
2020-09-27 6:34 ` [PATCH v4 1/7] iommu: Handle freelists when using deferred flushing in iommu drivers Lu Baolu
2020-09-27 6:34 ` [PATCH v4 2/7] iommu: Add iommu_dma_free_cpu_cached_iovas() Lu Baolu
2020-09-27 6:34 ` [PATCH v4 3/7] iommu: Allow the dma-iommu api to use bounce buffers Lu Baolu
2020-09-27 6:34 ` [PATCH v4 4/7] iommu: Add quirk for Intel graphic devices in map_sg Lu Baolu
2020-11-03 12:00 ` Robin Murphy [this message]
2020-09-27 6:34 ` [PATCH v4 5/7] iommu/vt-d: Update domain geometry in iommu_ops.at(de)tach_dev Lu Baolu
2020-09-27 6:34 ` [PATCH v4 6/7] iommu/vt-d: Convert intel iommu driver to the iommu ops Lu Baolu
2020-09-27 6:34 ` [PATCH v4 7/7] iommu/vt-d: Cleanup after converting to dma-iommu ops Lu Baolu
2020-09-28 9:44 ` [PATCH v4 0/7] Convert the intel iommu driver to the dma-iommu api Tvrtko Ursulin
2020-09-29 0:11 ` Lu Baolu
2020-10-01 12:17 ` Joerg Roedel
2020-10-02 11:59 ` Lu Baolu
2020-10-12 8:44 ` Tvrtko Ursulin
2020-10-13 0:32 ` Lu Baolu
2020-11-02 2:00 ` Lu Baolu
2020-11-02 11:52 ` Tvrtko Ursulin
2020-11-03 2:53 ` Lu Baolu
2020-11-03 9:14 ` Tvrtko Ursulin
2020-11-03 9:58 ` Joonas Lahtinen
2020-11-03 10:54 ` Joerg Roedel
2020-11-20 10:20 ` Lu Baolu
2020-10-01 21:17 ` Logan Gunthorpe
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