[PATCH 4.19 31/37] iommu/vt-d: Gracefully handle DMAR units with no supported address widths

Greg Kroah-Hartman
2021-02-02T15:07:54Z

From: David Woodhouse <dwmw@amazon.co.uk>

commit c40aaaac1018ff1382f2d35df5129a6bcea3df6b upstream.

Instead of bailing out completely, such a unit can still be used for
interrupt remapping.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/linux-iommu/549928db2de6532117f36c9c810373c14cf76f51.camel@infradead.org/
Signed-off-by: Joerg Roedel <jroedel@suse.de>
[ context change due to moving drivers/iommu/dmar.c to
drivers/iommu/intel/dmar.c ]
Signed-off-by: Filippo Sironi <sironi@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iommu/dmar.c | 46 +++++++++++++++++++++++++++++++---------------
1 file changed, 31 insertions(+), 15 deletions(-)

--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1029,8 +1029,8 @@ static int alloc_iommu(struct dmar_drhd_
{
struct intel_iommu *iommu;
u32 ver, sts;
- int agaw = 0;
- int msagaw = 0;
+ int agaw = -1;
+ int msagaw = -1;
int err;

if (!drhd->reg_base_addr) {
@@ -1055,17 +1055,28 @@ static int alloc_iommu(struct dmar_drhd_
}

err = -EINVAL;
- agaw = iommu_calculate_agaw(iommu);
- if (agaw < 0) {
- pr_err("Cannot get a valid agaw for iommu (seq_id = %d)\n",
- iommu->seq_id);
- goto err_unmap;
- }
- msagaw = iommu_calculate_max_sagaw(iommu);
- if (msagaw < 0) {
- pr_err("Cannot get a valid max agaw for iommu (seq_id = %d)\n",
- iommu->seq_id);
- goto err_unmap;
+ if (cap_sagaw(iommu->cap) == 0) {
+ pr_info("%s: No supported address widths. Not attempting DMA translation.\n",
+ iommu->name);
+ drhd->ignored = 1;
+ }
+
+ if (!drhd->ignored) {
+ agaw = iommu_calculate_agaw(iommu);
+ if (agaw < 0) {
+ pr_err("Cannot get a valid agaw for iommu (seq_id = %d)\n",
+ iommu->seq_id);
+ drhd->ignored = 1;
+ }
+ }
+ if (!drhd->ignored) {
+ msagaw = iommu_calculate_max_sagaw(iommu);
+ if (msagaw < 0) {
+ pr_err("Cannot get a valid max agaw for iommu (seq_id = %d)\n",
+ iommu->seq_id);
+ drhd->ignored = 1;
+ agaw = -1;
+ }
}
iommu->agaw = agaw;
iommu->msagaw = msagaw;
@@ -1092,7 +1103,12 @@ static int alloc_iommu(struct dmar_drhd_

raw_spin_lock_init(&iommu->register_lock);

- if (intel_iommu_enabled) {
+ /*
+ * This is only for hotplug; at boot time intel_iommu_enabled won't
+ * be set yet. When intel_iommu_init() runs, it registers the units
+ * present at boot time, then sets intel_iommu_enabled.
+ */
+ if (intel_iommu_enabled && !drhd->ignored) {
err = iommu_device_sysfs_add(&iommu->iommu, NULL,
intel_iommu_groups,
"%s", iommu->name);
@@ -1121,7 +1137,7 @@ error:

static void free_iommu(struct intel_iommu *iommu)
{
- if (intel_iommu_enabled) {
+ if (intel_iommu_enabled && iommu->iommu.ops) {
iommu_device_unregister(&iommu->iommu);
iommu_device_sysfs_remove(&iommu->iommu);
}