linux-kernel - [PATCH] iommu/amd: Ensure GA log notifier callbacks finish running before module unload

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Message-ID: <20250315031048.2374109-1-seanjc@google.com>
Date: Fri, 14 Mar 2025 20:10:48 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Joerg Roedel <joro@...tes.org>
Cc: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH] 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@...gle.com>
---
 drivers/iommu/amd/iommu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index b48a72bd7b23..b314523d9194 100644
--- 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);

base-commit: ea9bd29a9c0d757b3384ae3e633e6bbaddf00725
-- 
2.49.0.rc1.451.g8f38331e32-goog