[Xen-devel] [PATCH] xen/arm: iommu: Panic if not all IOMMUs are initialized

* [Xen-devel] [PATCH] xen/arm: iommu: Panic if not all IOMMUs are initialized
@ 2019-08-20 12:22 Julien Grall
  2019-08-20 14:28 ` Oleksandr
  0 siblings, 1 reply; 4+ messages in thread
From: Julien Grall @ 2019-08-20 12:22 UTC (permalink / raw)
  To: xen-devel
  Cc: Oleksandr Tyshchenko, Julien Grall, Stefano Stabellini,
	Volodymyr Babchuk

At the moment, the platform can come up with only part of the IOMMUs
initialized. This could lead to a failure later on when building the
hardware domain or even trying to assign a device to a guest.

To avoid unwanted behavior, Xen will not continue if one of the IOMMUs
has not been initialized correctly.

Signed-off-by: Julien Grall <julien.grall@arm.com>

---

Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

Basically, this is similar to forcing the use of IOMMU (i.e
iommu=force). Maybe we should drop the panic in setup.c and just
set force_iommu. Any opinion?
---
 xen/arch/arm/setup.c                | 5 ++++-
 xen/drivers/passthrough/arm/iommu.c | 8 ++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 7509d76dd4..f8a4064d3e 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -755,6 +755,7 @@ void __init start_xen(unsigned long boot_phys_offset,
         .max_grant_frames = gnttab_dom0_frames(),
         .max_maptrack_frames = opt_max_maptrack_frames,
     };
+    int rc;
 
     dcache_line_bytes = read_dcache_line_bytes();
 
@@ -892,7 +893,9 @@ void __init start_xen(unsigned long boot_phys_offset,
 
     setup_virt_paging();
 
-    iommu_setup();
+    rc = iommu_setup();
+    if ( !iommu_enabled && rc != -ENODEV )
+        panic("Couldn't configure correctly all the IOMMUs.");
 
     do_initcalls();
 
diff --git a/xen/drivers/passthrough/arm/iommu.c b/xen/drivers/passthrough/arm/iommu.c
index 2135233736..f219de9ac3 100644
--- a/xen/drivers/passthrough/arm/iommu.c
+++ b/xen/drivers/passthrough/arm/iommu.c
@@ -51,6 +51,14 @@ int __init iommu_hardware_setup(void)
         rc = device_init(np, DEVICE_IOMMU, NULL);
         if ( !rc )
             num_iommus++;
+        /*
+         * Ignore the following error codes:
+         *   - EBADF: Indicate the current not is not an IOMMU
+         *   - ENODEV: The IOMMU is not present or cannot be used by
+         *     Xen.
+         */
+        else if ( rc != -EBADF && rc != -ENODEV )
+            return rc;
     }
 
     return ( num_iommus > 0 ) ? 0 : -ENODEV;
-- 
2.11.0


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