iommu/amd: Make iommu_disable safer

BugLink: https://bugs.launchpad.net/bugs/1863019
[ Upstream commit 3ddbe913e55516d3e2165d43d4d5570761769878 ]

Make it safe to call iommu_disable during early init error conditions
before mmio_base is set, but after the struct amd_iommu has been added
to the amd_iommu_list. For example, this happens if firmware fails to
fill in mmio_phys in the ACPI table leading to a NULL pointer
dereference in iommu_feature_disable.

Fixes: 2c0ae1720c09c ('iommu/amd: Convert iommu initialization to state machine')
Signed-off-by: Kevin Mitchell <kevmitch@arista.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 4b8d353b7acf5ca3f1fb20ab20426813c2b5590a..3e3cc7e07702902f7153a987bae78408e71c3f61 100644 (file)
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -421,6 +421,9 @@ static void iommu_enable(struct amd_iommu *iommu)
 
 static void iommu_disable(struct amd_iommu *iommu)
 {
+       if (!iommu->mmio_base)
+               return;
+
        /* Disable command buffer */
        iommu_feature_disable(iommu, CONTROL_CMDBUF_EN);