[PATCH 1/2 for Linux 5.4] iommu/vt-d: Gracefully handle DMAR units with no supported address widths

Filippo Sironi
2021-02-02T00:01:52Z

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>
---
drivers/iommu/dmar.c | 44 ++++++++++++++++++++++++++++++--------------
1 file changed, 30 insertions(+), 14 deletions(-)

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index 30ac0ba55864..a5f69d9bb0b8 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1020,8 +1020,8 @@ static int alloc_iommu(struct dmar_drhd_unit *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) {
@@ -1046,17 +1046,28 @@ static int alloc_iommu(struct dmar_drhd_unit *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;
+ if (cap_sagaw(iommu->cap) == 0) {
+ pr_info("%s: No supported address widths. Not attempting DMA translation.\n",
+ iommu->name);
+ drhd->ignored = 1;
}
- 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 (!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;
@@ -1083,7 +1094,12 @@ static int alloc_iommu(struct dmar_drhd_unit *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);
@@ -1112,7 +1128,7 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)

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);
}
--
2.17.1

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