linux-kernel - [PATCH v2] iommu/vt-d: avoid unnecessory panic if iommu init fail in tboot system

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Message-Id: <20201110071908.3133-1-zhenzhong.duan@gmail.com>
Date:   Tue, 10 Nov 2020 15:19:08 +0800
From:   Zhenzhong Duan <zhenzhong.duan@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     ning.sun@...el.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, dwmw2@...radead.org,
        baolu.lu@...ux.intel.com, joro@...tes.org,
        iommu@...ts.linux-foundation.org,
        tboot-devel@...ts.sourceforge.net,
        Zhenzhong Duan <zhenzhong.duan@...il.com>
Subject: [PATCH v2] iommu/vt-d: avoid unnecessory panic if iommu init fail in tboot system

"intel_iommu=off" command line is used to disable iommu but iommu is force
enabled in a tboot system for security reason.

However for better performance on high speed network device, a new option
"intel_iommu=tboot_noforce" is introduced to disable the force on.

By default kernel should panic if iommu init fail in tboot for security
reason, but it's unnecessory if we use "intel_iommu=tboot_noforce,off".

Fix the code setting force_on and move intel_iommu_tboot_noforce
from tboot code to intel iommu code.

Fixes: 7304e8f28bb2 ("iommu/vt-d: Correctly disable Intel IOMMU force on")
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...il.com>
---
v2: move ckeck of intel_iommu_tboot_noforce into iommu code per Baolu.

 arch/x86/kernel/tboot.c     | 3 ---
 drivers/iommu/intel/iommu.c | 5 +++--
 include/linux/intel-iommu.h | 1 -
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index 992fb14..420be87 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -514,9 +514,6 @@ int tboot_force_iommu(void)
 	if (!tboot_enabled())
 		return 0;
 
-	if (intel_iommu_tboot_noforce)
-		return 1;
-
 	if (no_iommu || swiotlb || dmar_disabled)
 		pr_warn("Forcing Intel-IOMMU to enabled\n");
 
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 1b1ca63..4d9b298 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -179,7 +179,7 @@ static inline unsigned long virt_to_dma_pfn(void *p)
  * (used when kernel is launched w/ TXT)
  */
 static int force_on = 0;
-int intel_iommu_tboot_noforce;
+static int intel_iommu_tboot_noforce;
 static int no_platform_optin;
 
 #define ROOT_ENTRY_NR (VTD_PAGE_SIZE/sizeof(struct root_entry))
@@ -4885,7 +4885,8 @@ int __init intel_iommu_init(void)
 	 * Intel IOMMU is required for a TXT/tboot launch or platform
 	 * opt in, so enforce that.
 	 */
-	force_on = tboot_force_iommu() || platform_optin_force_iommu();
+	force_on = (!intel_iommu_tboot_noforce && tboot_force_iommu()) ||
+		    platform_optin_force_iommu();
 
 	if (iommu_init_mempool()) {
 		if (force_on)
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index fbf5b3e..d956987 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -798,7 +798,6 @@ struct context_entry *iommu_context_addr(struct intel_iommu *iommu, u8 bus,
 extern int iommu_calculate_max_sagaw(struct intel_iommu *iommu);
 extern int dmar_disabled;
 extern int intel_iommu_enabled;
-extern int intel_iommu_tboot_noforce;
 extern int intel_iommu_gfx_mapped;
 #else
 static inline int iommu_calculate_agaw(struct intel_iommu *iommu)
-- 
1.8.3.1