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Re: [Xen-devel] [PATCH v5 3/5] ARM: ITS: Deny hardware domain access to ITS



Hi Manish,

I just spotted an issue in this patch.

On 10/10/17 07:16, mjaggi@xxxxxxxxxxxxxxxxxx wrote:
From: Manish Jaggi <mjaggi@xxxxxxxxxx>

This patch extends the gicv3_iomem_deny_access functionality by adding
support for ITS region as well. Add function gicv3_its_deny_access.

Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxx>
Signed-off-by: Manish Jaggi <mjaggi@xxxxxxxxxx>
---
  xen/arch/arm/gic-v3-its.c        | 22 ++++++++++++++++++++++
  xen/arch/arm/gic-v3.c            |  3 +++
  xen/include/asm-arm/gic_v3_its.h |  9 +++++++++
  3 files changed, 34 insertions(+)

diff --git a/xen/arch/arm/gic-v3-its.c b/xen/arch/arm/gic-v3-its.c
index 3023ee5..7746ae8 100644
--- a/xen/arch/arm/gic-v3-its.c
+++ b/xen/arch/arm/gic-v3-its.c
@@ -21,6 +21,7 @@
  #include <xen/acpi.h>
  #include <xen/lib.h>
  #include <xen/delay.h>
+#include <xen/iocap.h>
  #include <xen/libfdt/libfdt.h>
  #include <xen/mm.h>
  #include <xen/rbtree.h>
@@ -905,6 +906,27 @@ struct pending_irq *gicv3_assign_guest_event(struct domain 
*d,
      return pirq;
  }
+int gicv3_its_deny_access(const struct domain *d)
+{
+    int rc = 0;
+    unsigned long mfn, nr;
+    const struct host_its *its_data;
+
+    list_for_each_entry( its_data, &host_its_list, entry )
+    {
+        mfn = paddr_to_pfn(its_data->addr);
+        nr = PFN_UP(GICV3_ITS_SIZE);

While you fix the bug (see below), please use its_data->size here.

+        rc = iomem_deny_access(d, mfn, mfn + nr);
+        if ( rc )
+        {
+            printk( "iomem_deny_access failed for %lx:%lx \r\n", mfn, nr);

And here the spurious space between ( and ".

+            break;
+        }
+    }
+
+    return rc;
+}
+
  /*
   * Create the respective guest DT nodes from a list of host ITSes.
   * This copies the reg property, so the guest sees the ITS at the same address
diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
index 6f562f4..b3d605d 100644
--- a/xen/arch/arm/gic-v3.c
+++ b/xen/arch/arm/gic-v3.c
@@ -1308,6 +1308,9 @@ static int gicv3_iomem_deny_access(const struct domain *d)
      if ( rc )
          return rc;
+ if ( gicv3_its_deny_access(d) )
+        return rc;

you return rc here in case of an error, however you don't set it before. So this will always return 0 and Xen will continue to boot as nothing happen.

The best way to fix it would be:

rc = gicv3_its_deny_access(d);
if ( rc )
  return rc;

+
      for ( i = 0; i < gicv3.rdist_count; i++ )
      {
          mfn = gicv3.rdist_regions[i].base >> PAGE_SHIFT;
diff --git a/xen/include/asm-arm/gic_v3_its.h b/xen/include/asm-arm/gic_v3_its.h
index e1be33c..31fca66 100644
--- a/xen/include/asm-arm/gic_v3_its.h
+++ b/xen/include/asm-arm/gic_v3_its.h
@@ -139,6 +139,10 @@ void gicv3_its_dt_init(const struct dt_device_node *node);
  #ifdef CONFIG_ACPI
  void gicv3_its_acpi_init(void);
  #endif
+
+/* Deny iomem access for its */
+int gicv3_its_deny_access(const struct domain *d);
+
  bool gicv3_its_host_has_its(void);
unsigned int vgic_v3_its_count(const struct domain *d);
@@ -206,6 +210,11 @@ static inline void gicv3_its_acpi_init(void)
  }
  #endif
+static inline int gicv3_its_deny_access(const struct domain *d)
+{
+    return 0;
+}
+
  static inline bool gicv3_its_host_has_its(void)
  {
      return false;


Cheers,

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