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SubjectRe: [PATCH] iommu/dart: Fix apple_dart_device_group for PCI groups
On Sat, 28 Jan 2023 at 11:43, Sven Peter <sven@svenpeter.dev> wrote:
>
> pci_device_group() can return an already existing IOMMU group if the PCI
> device's pagetables have to be shared with another one due to bus
> toplogy, isolation features and/or DMA alias quirks.
> apple_dart_device_group() however assumes that the group has just been
> created and overwrites its iommudata which will eventually lead to
> apple_dart_release_group leaving stale entries in sid2group.
> Fix that by merging the iommudata if the returned group already exists.
>
> Fixes: f0b636804c7c ("iommu/dart: Clear sid2group entry when a group is freed")
> Signed-off-by: Sven Peter <sven@svenpeter.dev>
> ---

Reviewed-by: Eric Curtin <ecurtin@redhat.com>

Is mise le meas/Regards,

Eric Curtin

> drivers/iommu/apple-dart.c | 51 ++++++++++++++++++++++++++++++++------
> 1 file changed, 44 insertions(+), 7 deletions(-)
>
> This won't apply cleanly to iommu/fixes as it's based on the t8110 DART
> changes since the USB4/Thunderbolt DART itself also depends on those.
> That's not a big deal though since it's not possible to run into this
> bug without complex PCI bus topologies which can only be created using
> USB4/Thunderbolt on these SoCs and there's no support for that upstream
> yet.
>
> diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
> index a1304ba3639b..02f7a1740b14 100644
> --- a/drivers/iommu/apple-dart.c
> +++ b/drivers/iommu/apple-dart.c
> @@ -840,6 +840,29 @@ static void apple_dart_release_group(void *iommu_data)
> mutex_unlock(&apple_dart_groups_lock);
> }
>
> +static int apple_dart_merge_master_cfg(struct apple_dart_master_cfg *dst,
> + struct apple_dart_master_cfg *src)
> +{
> + /*
> + * We know that this function is only called for groups returned from
> + * pci_device_group and that all Apple Silicon platforms never spread
> + * PCIe devices from the same bus across multiple DARTs such that we can
> + * just assume that both src and dst only have the same single DART.
> + */
> + if (src->stream_maps[1].dart)
> + return -EINVAL;
> + if (dst->stream_maps[1].dart)
> + return -EINVAL;
> + if (src->stream_maps[0].dart != dst->stream_maps[0].dart)
> + return -EINVAL;
> +
> + bitmap_or(dst->stream_maps[0].sidmap,
> + dst->stream_maps[0].sidmap,
> + src->stream_maps[0].sidmap,
> + dst->stream_maps[0].dart->num_streams);
> + return 0;
> +}
> +
> static struct iommu_group *apple_dart_device_group(struct device *dev)
> {
> int i, sid;
> @@ -881,14 +904,28 @@ static struct iommu_group *apple_dart_device_group(struct device *dev)
> if (!group)
> goto out;
>
> - group_master_cfg = kmemdup(cfg, sizeof(*group_master_cfg), GFP_KERNEL);
> - if (!group_master_cfg) {
> - iommu_group_put(group);
> - goto out;
> - }
> + group_master_cfg = iommu_group_get_iommudata(group);
> + if (group_master_cfg) {
> + int ret;
>
> - iommu_group_set_iommudata(group, group_master_cfg,
> - apple_dart_release_group);
> + ret = apple_dart_merge_master_cfg(group_master_cfg, cfg);
> + if (ret) {
> + dev_err(dev, "Failed to merge DART IOMMU grups.\n");
> + iommu_group_put(group);
> + res = ERR_PTR(ret);
> + goto out;
> + }
> + } else {
> + group_master_cfg = kmemdup(cfg, sizeof(*group_master_cfg),
> + GFP_KERNEL);
> + if (!group_master_cfg) {
> + iommu_group_put(group);
> + goto out;
> + }
> +
> + iommu_group_set_iommudata(group, group_master_cfg,
> + apple_dart_release_group);
> + }
>
> for_each_stream_map(i, cfg, stream_map)
> for_each_set_bit(sid, stream_map->sidmap, stream_map->dart->num_streams)
> --
> 2.25.1
>
>

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