iommu/amd: Ensure GA log notifier callbacks finish running before module unload

Synchronize RCU when unregistering KVM's GA log notifier to ensure all
in-flight interrupt handlers complete before KVM-the module is unloaded.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20250315031048.2374109-1-seanjc@google.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index be8761bbef0ffbd2755665421f9fcaceb7774c8d..15e3342648811a999689128d612b25c0774003ef 100644 (file)
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -982,6 +982,14 @@ int amd_iommu_register_ga_log_notifier(int (*notifier)(u32))
 {
        iommu_ga_log_notifier = notifier;
 
+       /*
+        * Ensure all in-flight IRQ handlers run to completion before returning
+        * to the caller, e.g. to ensure module code isn't unloaded while it's
+        * being executed in the IRQ handler.
+        */
+       if (!notifier)
+               synchronize_rcu();
+
        return 0;
 }
 EXPORT_SYMBOL(amd_iommu_register_ga_log_notifier);