xen/arm: vgic-v3: Don't create empty re-distributor regions

At the moment, Xen is assuming the hardware domain will have the same
number of re-distributor regions as the host. However, as the
number of CPUs or the stride (e.g on GICv4) may be different we end up
exposing regions which does not contain any re-distributors.

When booting, Linux will go through all the re-distributor region to
check whether a property (e.g vPLIs) is available accross all the
re-distributors. This will result to a data abort on empty regions
because there are no underlying re-distributor.

So we need to limit the number of regions exposed to the hardware
domain. The code reworked to only expose the minimun number of regions
required by the hardware domain. It is assumed the regions will be
populated starting from the first one.

Lastly, rename vgic_v3_rdist_count to reflect the value return by the
helper.

Reported-by: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Julien Grall <julien.grall@arm.com>
Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
(cherry picked from commit 54ec59f6b0b363c34cf1864d5214a05e35ea75ee)

diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
index d2b0b1e5b3c6419df616e70c309e23ef297e9d56..6d7243131b23a1440dcdcddc3009e990a7b6bdc8 100644 (file)
--- a/xen/arch/arm/gic-v3.c
+++ b/xen/arch/arm/gic-v3.c
@@ -1151,6 +1151,8 @@ static int gicv3_make_hwdom_dt_node(const struct domain *d,
      * GIC has two memory regions: Distributor + rdist regions
      * CPU interface and virtual cpu interfaces accessesed as System registers
      * So cells are created only for Distributor and rdist regions
+     * The hardware domain may not use all the regions. So only copy
+     * what is necessary.
      */
     len = len * (d->arch.vgic.nr_regions + 1);
     new_cells = xzalloc_bytes(len);
@@ -1383,6 +1385,10 @@ static int gicv3_make_hwdom_madt(const struct domain *d, u32 offset)
 
     /* Add Generic Redistributor */
     size = sizeof(struct acpi_madt_generic_redistributor);
+    /*
+     * The hardware domain may not used all the regions. So only copy
+     * what is necessary.
+     */
     for ( i = 0; i < d->arch.vgic.nr_regions; i++ )
     {
         gicr = (struct acpi_madt_generic_redistributor *)(base_ptr + table_len);

diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index 4d4c3d1f49c24b5dc07a2703ee3d71f333c4a777..257e7fd4f848ead7ef383443e30f2db2dd5012e3 100644 (file)
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -1448,7 +1448,11 @@ static int vgic_v3_vcpu_init(struct vcpu *v)
     return 0;
 }
 
-static inline unsigned int vgic_v3_rdist_count(struct domain *d)
+/*
+ * Return the maximum number possible of re-distributor regions for
+ * a given domain.
+ */
+static inline unsigned int vgic_v3_max_rdist_count(struct domain *d)
 {
     return is_hardware_domain(d) ? vgic_v3_hw.nr_rdist_regions :
                GUEST_GICV3_RDIST_REGIONS;
@@ -1460,7 +1464,7 @@ static int vgic_v3_real_domain_init(struct domain *d)
     int rdist_count, i, ret;
 
     /* Allocate memory for Re-distributor regions */
-    rdist_count = vgic_v3_rdist_count(d);
+    rdist_count = vgic_v3_max_rdist_count(d);
 
     rdist_regions = xzalloc_array(struct vgic_rdist_region, rdist_count);
     if ( !rdist_regions )
@@ -1499,7 +1503,18 @@ static int vgic_v3_real_domain_init(struct domain *d)
             d->arch.vgic.rdist_regions[i].first_cpu = first_cpu;
 
             first_cpu += size / d->arch.vgic.rdist_stride;
+
+            if ( first_cpu >= d->max_vcpus )
+                break;
         }
+
+        /*
+         * The hardware domain may not use all the re-distributors
+         * regions (e.g when the number of vCPUs does not match the
+         * number of pCPUs). Update the number of regions to avoid
+         * exposing unused region as they will not get emulated.
+         */
+        d->arch.vgic.nr_regions = i + 1;
     }
     else
     {
@@ -1582,7 +1597,7 @@ int vgic_v3_init(struct domain *d, int *mmio_count)
     }
 
     /* GICD region + number of Redistributors */
-    *mmio_count = vgic_v3_rdist_count(d) + 1;
+    *mmio_count = vgic_v3_max_rdist_count(d) + 1;
 
     register_vgic_ops(d, &v3_ops);