5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kevin Tian <kevin.tian@intel.com>
commit 219cc978d69ce9b538d0d73936c569d4ca5b0a24 upstream.
If user explicitly requests to disable iommu (via "iommu=off" or
"intel_iommu=off"), there is no reason to force enabling it due
to platform opt-in (for external-facing devices). User should be
aware of any security implication of doing so.
"intel_iommu=off" implements this policy by setting no_platform_optin
to skip platform opt-in in platform_optin_force_iommu().
However, "iommu=off" (no_iommu=1) doesn't set no_platform_optin
hence is broken in this aspect:
- detect_intel_iommu() doesn't request ACS if no_iommu=1
- platform_optin_force_iommu() forces iommu on if external-facing
devices exist and no_platform_optin is not set
This leads to a bad configuration with ACS disabled while DMA
remapping is enabled.
Instead of setting no_platform_optin (will soon be removed) for
no_iommu=1, directly check no_iommu in platform_optin_force_iommu().
Fixes: 89a6079df791 ("iommu/vt-d: Force IOMMU on for platform opt in hint")
Cc: <redacted>
Signed-off-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iommu/intel/iommu.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4243,10 +4243,11 @@ static inline bool has_external_pci(void
static int __init platform_optin_force_iommu(void)
{
- if (!dmar_platform_optin() || no_platform_optin || !has_external_pci())
+ if (no_iommu || !dmar_platform_optin() || no_platform_optin ||
+ !has_external_pci())
return 0;
- if (no_iommu || dmar_disabled)
+ if (dmar_disabled)
pr_info("Intel-IOMMU force enabled due to platform opt in\n");
/*@@ -4257,7 +4258,6 @@ static int __init platform_optin_force_i
iommu_set_default_passthrough(false);
dmar_disabled = 0;
- no_iommu = 0;
return 1;
}