linux-kernel - [RFC PATCH 03/15] iommu/vt-d: Prevent hotplugs when live update state is not normal

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Message-ID: <20250928190624.3735830-4-skhawaja@google.com>
Date: Sun, 28 Sep 2025 19:06:11 +0000
From: Samiullah Khawaja <skhawaja@...gle.com>
To: David Woodhouse <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>, 
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, 
	Pasha Tatashin <pasha.tatashin@...een.com>, Jason Gunthorpe <jgg@...pe.ca>, iommu@...ts.linux.dev
Cc: Samiullah Khawaja <skhawaja@...gle.com>, Robin Murphy <robin.murphy@....com>, 
	Pratyush Yadav <pratyush@...nel.org>, Kevin Tian <kevin.tian@...el.com>, linux-kernel@...r.kernel.org, 
	Saeed Mahameed <saeedm@...dia.com>, Adithya Jayachandran <ajayachandra@...dia.com>, 
	Parav Pandit <parav@...dia.com>, Leon Romanovsky <leonro@...dia.com>, William Tu <witu@...dia.com>, 
	Vipin Sharma <vipinsh@...gle.com>, dmatlack@...gle.com, zhuyifei@...gle.com, 
	Chris Li <chrisl@...nel.org>, praan@...gle.com
Subject: [RFC PATCH 03/15] iommu/vt-d: Prevent hotplugs when live update state
 is not normal

Hotplugs should not be allowed when the live update state is not normal.
This means either we have preserved the state of IOMMU hardware units or
restoring the preserved state.

The live update semaphore read lock should be taken before checking the
live update state.

Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
---
 drivers/iommu/intel/dmar.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index ec975c73cfe6..248bc7e9b035 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -26,6 +26,7 @@
 #include <linux/dmi.h>
 #include <linux/slab.h>
 #include <linux/iommu.h>
+#include <linux/liveupdate.h>
 #include <linux/numa.h>
 #include <linux/limits.h>
 #include <asm/irq_remapping.h>
@@ -2357,6 +2358,10 @@ static int dmar_device_hotplug(acpi_handle handle, bool insert)
 	if (tmp == NULL)
 		return 0;
 
+	guard_liveupdate_state_read();
+	if (!liveupdate_state_normal())
+		return -EBUSY;
+
 	down_write(&dmar_global_lock);
 	if (insert)
 		ret = dmar_hotplug_insert(tmp);
-- 
2.51.0.536.g15c5d4f767-goog