[Xen-devel] [RFC PATCH 02/49] ARM: vGICv3: drop GUEST_GICV3_RDIST_REGIONS symbol

[Andre Przywara <andre.przywara@xxxxxxxxxx>]

Architecturally there is only one GICv3 redistributor region.
Drop the symbol which suggested that was a delibarate choice for Xen
guests, instead hard code the "1" in the appropriate places, along with
a comment to explain the reasons.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
---
 xen/arch/arm/vgic-v3.c        | 17 ++++++++++++-----
 xen/include/public/arch-arm.h |  1 -
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index 2ad8a6be62..12338c6b21 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -1632,8 +1632,18 @@ static int vgic_v3_vcpu_init(struct vcpu *v)
 
 static inline unsigned int vgic_v3_rdist_count(struct domain *d)
 {
-    return is_hardware_domain(d) ? vgic_v3_hw.nr_rdist_regions :
-               GUEST_GICV3_RDIST_REGIONS;
+    /*
+     * Architecturally there is only one GICv3 redistributor region.
+     * The GICv3 DT binding provisions for multiple regions, since there are
+     * platforms out there which break this architectural assumption.
+     * ACPI does not support this workaround at all.
+     * For Dom0 we have to live with the MMIO layout the hardware provides,
+     * so we have to copy the multiple regions - as the first region may not
+     * provide enough space to hold all redistributors we need.
+     * However DomU get a constructed memory map, so we can go with
+     * the architected single redistributor region.
+     */
+    return is_hardware_domain(d) ? vgic_v3_hw.nr_rdist_regions : 1;
 }
 
 static int vgic_v3_domain_init(struct domain *d)
@@ -1692,9 +1702,6 @@ static int vgic_v3_domain_init(struct domain *d)
     {
         d->arch.vgic.dbase = GUEST_GICV3_GICD_BASE;
 
-        /* XXX: Only one Re-distributor region mapped for the guest */
-        BUILD_BUG_ON(GUEST_GICV3_RDIST_REGIONS != 1);
-
         d->arch.vgic.rdist_stride = GUEST_GICV3_RDIST_STRIDE;
 
         /* The first redistributor should contain enough space for all CPUs */
diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
index 05fd11ca38..ca79ab6284 100644
--- a/xen/include/public/arch-arm.h
+++ b/xen/include/public/arch-arm.h
@@ -402,7 +402,6 @@ typedef uint64_t xen_callback_t;
 #define GUEST_GICV3_GICD_SIZE      xen_mk_ullong(0x00010000)
 
 #define GUEST_GICV3_RDIST_STRIDE   xen_mk_ullong(0x00020000)
-#define GUEST_GICV3_RDIST_REGIONS  1
 
 #define GUEST_GICV3_GICR0_BASE     xen_mk_ullong(0x03020000) /* vCPU0..127 */
 #define GUEST_GICV3_GICR0_SIZE     xen_mk_ullong(0x01000000)
-- 
2.14.1


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