| Message ID | 20200927063437.13988-5-baolu.lu@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Convert the intel iommu driver to the dma-iommu api | expand |
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); >
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; + } + for_each_sg(sg, s, nents, i) { /* Restore this segment's original unaligned fields first */ unsigned int s_iova_off = sg_dma_address(s);