From: Joerg Roedel <jroedel@xxxxxxx>
Add this option to enable the IOMMU on platforms like AMD Stoney,
where the kernel usually disables it because it may cause problems in
some scenarios.
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 3 +++
drivers/iommu/amd/init.c | 7 +++++++
2 files changed, 10 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 04545725f187..c9573f726707 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -303,6 +303,9 @@
allowed anymore to lift isolation
requirements as needed. This option
does not override iommu=pt
+ force_enable - Force enable the IOMMU on platforms known
+ to be buggy with IOMMU enabled. Use this
+ option with care.
amd_iommu_dump= [HW,X86-64]
Enable AMD IOMMU driver option to dump the ACPI table
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 321f5906e6ed..3e2295d3b3e2 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -155,6 +155,7 @@ static int amd_iommu_xt_mode = IRQ_REMAP_XAPIC_MODE;
static bool amd_iommu_detected;
static bool __initdata amd_iommu_disabled;
+static bool __initdata amd_iommu_force_enable;
static int amd_iommu_target_ivhd_type;
u16 amd_iommu_last_bdf; /* largest PCI device id we have
@@ -2882,6 +2883,9 @@ static bool detect_ivrs(void)
acpi_put_table(ivrs_base);
+ if (amd_iommu_force_enable)
+ goto out;
+
/* Don't use IOMMU if there is Stoney Ridge graphics */
for (i = 0; i < 32; i++) {
u32 pci_id;
@@ -2893,6 +2897,7 @@ static bool detect_ivrs(void)
}
}
+out:
/* Make sure ACS will be enabled during PCI probe */
pci_request_acs();
@@ -3148,6 +3153,8 @@ static int __init parse_amd_iommu_options(char *str)
for (; *str; ++str) {
if (strncmp(str, "fullflush", 9) == 0)
amd_iommu_unmap_flush = true;
+ if (strncmp(str, "force_enable", 12) == 0)
+ amd_iommu_force_enable = true;
if (strncmp(str, "off", 3) == 0)
amd_iommu_disabled = true;
if (strncmp(str, "force_isolation", 15) == 0)
--
2.31.1
