[Xen-devel] [PATCH v3 06/15] xen/arm: vgic-v3: Set stride during domain initialization

[Julien Grall <julien.grall@xxxxxxxxxx>]

The stride may not be set if the hardware GIC is using the default
layout. It happens on the Foundation model.

On GICv3, the default stride is 2 * 64K. Therefore it's possible to avoid
checking at every redistributor MMIO access if the stride is not set.

Because domU uses a static stride configuration this only happens for
dom0, so we can move this code in gicv_v3_init. Take the opportunity to move
the stride setting a bit earlier because the loop to set regions will require
the stride.

Also, use 2 * 64K rather than 128K and explain the reason.

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

---
    I wasn't not sure where to move this code. I find very confusion the
    splitting between vgic and gicv. Maybe we should introduce a
    hwdom_gicv_init and giccc_map callbacks. Then move most of the
    initialization in the vgic one.

    Changes in v3:
        - Fix typoes and update commit message
        - Forgot to remove the check on the stride the rdist write

    Changes in v2:
        - Patch added
---
 xen/arch/arm/gic-v3.c  | 11 ++++++++++-
 xen/arch/arm/vgic-v3.c | 12 ++----------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
index 47452ca..7b33ff7 100644
--- a/xen/arch/arm/gic-v3.c
+++ b/xen/arch/arm/gic-v3.c
@@ -897,12 +897,21 @@ static int gicv_v3_init(struct domain *d)
     {
         d->arch.vgic.dbase = gicv3.dbase;
         d->arch.vgic.dbase_size = gicv3.dbase_size;
+
+        d->arch.vgic.rdist_stride = gicv3.rdist_stride;
+        /*
+         * If the stride is not set, the default stride for GICv3 is 2 * 64K:
+         *     - first 64k page for Control and Physical LPIs
+         *     - second 64k page for Control and Generation of SGIs
+         */
+        if ( !d->arch.vgic.rdist_stride )
+            d->arch.vgic.rdist_stride = 2 * SZ_64K;
+
         for ( i = 0; i < gicv3.rdist_count; i++ )
         {
             d->arch.vgic.rbase[i] = gicv3.rdist_regions[i].base;
             d->arch.vgic.rbase_size[i] = gicv3.rdist_regions[i].size;
         }
-        d->arch.vgic.rdist_stride = gicv3.rdist_stride;
         d->arch.vgic.rdist_count = gicv3.rdist_count;
     }
     else
diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index 2c14717..c5a743a 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -625,11 +625,7 @@ static int vgic_v3_rdistr_mmio_read(struct vcpu *v, 
mmio_info_t *info)
 
     perfc_incr(vgicr_reads);
 
-    if ( v->domain->arch.vgic.rdist_stride != 0 )
-        offset = info->gpa & (v->domain->arch.vgic.rdist_stride - 1);
-    else
-        /* If stride is not set. Default 128K */
-        offset = info->gpa & (SZ_128K - 1);
+    offset = info->gpa & (v->domain->arch.vgic.rdist_stride - 1);
 
     if ( offset < SZ_64K )
         return __vgic_v3_rdistr_rd_mmio_read(v, info, offset);
@@ -649,11 +645,7 @@ static int vgic_v3_rdistr_mmio_write(struct vcpu *v, 
mmio_info_t *info)
 
     perfc_incr(vgicr_writes);
 
-    if ( v->domain->arch.vgic.rdist_stride != 0 )
-        offset = info->gpa & (v->domain->arch.vgic.rdist_stride - 1);
-    else
-        /* If stride is not set. Default 128K */
-        offset = info->gpa & (SZ_128K - 1);
+    offset = info->gpa & (v->domain->arch.vgic.rdist_stride - 1);
 
     if ( offset < SZ_64K )
         return __vgic_v3_rdistr_rd_mmio_write(v, info, offset);
-- 
2.1.4


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