[PATCH v2] iommu/amd: remove obsolete domain pointer warning on release

[Kevin Mitchell <kevmitch@arista.com>]

A warning is triggered in amd_iommu_release_device() on removal of a
device with an IOMMU_RESV_DIRECT region. The warning is based on the
false assumption that correct attachment to the release_domain will
always result in a NULL dev_data->domain pointer. For devices with
IOMMU_RESV_DIRECT (and consequently dev->iommu->require_direct), the
release domain is the permanent identity_domain which sets
itself to dev_data->domain on attach.

This behaviour was added in commit e94160488e65 ("iommu: Generic support
for RMRs during device release"). Commit c21b34762e2f ("iommu/amd: Set
release_domain to blocked_domain") caused it to take effect for AMD
IOMMU.

Remove the warning as it is no longer strictly an error to have a non-NULL
domain pointer. As this leaves amd_iommu_release_device() empty, remove it.

The warning was observed for a device with direct mapped region:

/sys/bus/pci/devices/0000:04:00.0/iommu_group/reserved_regions:

  0x00000000fee00000 0x00000000feefffff msi
  0x000000fd00000000 0x000000ffffffffff reserved
  0x0000fffd00000000 0x0000ffffffffffff direct

Upon hotunplug:

[   28.715475] pcieport 0000:00:03.1: pciehp: Slot(0-3): Link Down
[   28.715482] pcieport 0000:00:03.1: pciehp: Slot(0-3): Card not present
[   28.715601] ------------[ cut here ]------------
[   28.715603] WARNING: drivers/iommu/amd/iommu.c:2521 at amd_iommu_release_device+0x5d/0x70, CPU#4: irq/29-pciehp/99
[   28.715657] RIP: 0010:amd_iommu_release_device+0x5d/0x70
[   28.715687] Call Trace:
[   28.715689]  <TASK>
[   28.715694]  iommu_deinit_device+0x84/0x110
[   28.715699]  __iommu_group_remove_device+0xa8/0xd0
[   28.715703]  iommu_bus_notifier+0x48/0x70
[   28.715707]  notifier_call_chain+0x48/0xe0
[   28.715712]  blocking_notifier_call_chain+0x45/0x60
[   28.715716]  bus_notify+0x3b/0x60
[   28.715720]  device_del+0x259/0x3b0
[   28.715730]  pci_remove_bus_device+0x85/0x100
[   28.715735]  pciehp_unconfigure_device+0x9d/0x180
[   28.715743]  __pciehp_disable_slot+0x47/0xe0
[   28.715747]  pciehp_handle_presence_or_link_change+0x80/0x5e0
[   28.715753]  pciehp_ist+0x162/0x290

Fixes: c21b34762e2f ("iommu/amd: Set release_domain to blocked_domain")
Cc: stable@vger.kernel.org
Signed-off-by: Kevin Mitchell <kevmitch@arista.com>
---
Changes in v2:
- Remove the warning alltogether as well as the now-empty
  amd_iommu_release_device()
- Link to v1: https://lore.kernel.org/r/20261008202530.14501-2-kevmitch@arista.com

 drivers/iommu/amd/iommu.c | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 56262f6b1f70..d07abc342247 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -489,6 +489,10 @@ static void setup_aliases(struct amd_iommu *iommu, struct device *dev)
 	clone_aliases(iommu, dev);
 }
 
+/*
+ * We keep dev_data around for unplugged devices and reuse it when the
+ * device is re-plugged - not doing so would introduce a ton of races.
+ */
 static struct iommu_dev_data *find_dev_data(struct amd_iommu *iommu, u16 devid)
 {
 	struct iommu_dev_data *dev_data;
@@ -2548,18 +2552,6 @@ static struct iommu_device *amd_iommu_probe_device(struct device *dev)
 	return iommu_dev;
 }
 
-static void amd_iommu_release_device(struct device *dev)
-{
-	struct iommu_dev_data *dev_data = dev_iommu_priv_get(dev);
-
-	WARN_ON(dev_data->domain);
-
-	/*
-	 * We keep dev_data around for unplugged devices and reuse it when the
-	 * device is re-plugged - not doing so would introduce a ton of races.
-	 */
-}
-
 static struct iommu_group *amd_iommu_device_group(struct device *dev)
 {
 	if (dev_is_pci(dev))
@@ -3205,7 +3197,6 @@ const struct iommu_ops amd_iommu_ops = {
 	.domain_alloc_paging_flags = amd_iommu_domain_alloc_paging_flags,
 	.domain_alloc_sva = amd_iommu_domain_alloc_sva,
 	.probe_device = amd_iommu_probe_device,
-	.release_device = amd_iommu_release_device,
 	.device_group = amd_iommu_device_group,
 	.get_resv_regions = amd_iommu_get_resv_regions,
 	.is_attach_deferred = amd_iommu_is_attach_deferred,
-- 
2.51.0