[Xen-devel] [PATCH v3 02/15] xen/arm: vgic-v3: Correctly set GICD_TYPER.CPUNumber

[Julien Grall <julien.grall@xxxxxxxxxx>]

On GICv3, the value (CPUNumber + 1) indicates the number of processor that may
be used as interrupts targets when ARE bit is zero. The maximum is 8
processors.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
    The current code of the vGIC doesn't support ARE = 0.
    Nonetheless, the patch is a candidate for backporing to Xen 4.5 to have a
    consistent vGIC driver.

    Changes in v2:
        - Rebase after the change in patch #1 and the introduction of
        nr_spis/vgic_num_irqs.
        - Add Ian's ack. I keep the ack has the changes was only
        rebasing.
---
 xen/arch/arm/vgic-v3.c    | 7 ++++++-
 xen/include/asm-arm/gic.h | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index 72b22ee..e0a7d5b 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -685,10 +685,15 @@ static int vgic_v3_distr_mmio_read(struct vcpu *v, 
mmio_info_t *info)
          * Stream Protocol Interface
          */
         unsigned int irq_bits = get_count_order(vgic_num_irqs(v->domain));
+        /*
+         * Number of processors that may be used as interrupt targets when ARE
+         * bit is zero. The maximum is 8.
+         */
+        unsigned int ncpus = min_t(unsigned int, v->domain->max_vcpus, 8);
 
         if ( dabt.size != DABT_WORD ) goto bad_width;
         /* No secure world support for guests. */
-        *r = (((v->domain->max_vcpus << 5) & GICD_TYPE_CPUS ) |
+        *r = ((ncpus - 1) << GICD_TYPE_CPUS_SHIFT |
               ((v->domain->arch.vgic.nr_spis / 32) & GICD_TYPE_LINES));
 
         *r |= (irq_bits - 1) << GICD_TYPE_ID_BITS_SHIFT;
diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index 187dc46..0396a8e 100644
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -93,6 +93,7 @@
 #define GICD_CTL_ENABLE 0x1
 
 #define GICD_TYPE_LINES 0x01f
+#define GICD_TYPE_CPUS_SHIFT 5
 #define GICD_TYPE_CPUS  0x0e0
 #define GICD_TYPE_SEC   0x400
 
-- 
2.1.4


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