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Re: [Xen-devel] [PATCH 2/7] ARM: vGICv3: drop GUEST_GICV3_RDIST_REGIONS symbol



Hi Andre,

On 24/01/18 14:35, Andre Przywara wrote:
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 af16dfd005..7d3ea171b4 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -1640,8 +1640,18 @@ 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.

This is not true. The ACPI spec supports multiple regions of redistributors. What ACPI does not support is a different stride.

+     * 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)
@@ -1700,9 +1710,6 @@ 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)


Cheers,

--
Julien Grall

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