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Re: [Xen-devel] [PATCH V2 1/8] xen/arm64: increase MAX_VIRT_CPUS to 128 on arm64

Hi Chen,

On 23/05/2015 14:52, Chen Baozi wrote:
From: Chen Baozi <baozich@xxxxxxxxx>

GIC-500 supports up to 128 cores in a single SoC. Increase MAX_VIRT_CPUS
to 128 on arm64.

This series have to be bisectable. Although, this patch will break compilation on ARM64 because you increased MAX_VIRT_CPUS without the re-distributor region (done in the next patch).

Furthermore, GICv2 is only supporting 8 CPUs. We don't have to allow a guest with more than 8 vCPUs when the GICv2 is in use.

Lastly, given that the support of 128 vCPUs will only worked when the last patch of this series is applied, I would move this patch at the end.

Signed-off-by: Chen Baozi <baozich@xxxxxxxxx>
  xen/arch/arm/vgic-v3.c       | 2 +-
  xen/include/asm-arm/config.h | 4 ++++
  2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index 45d54a2..40e1892 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -906,7 +906,7 @@ static int vgic_v3_distr_mmio_write(struct vcpu *v, 
mmio_info_t *info)
          rank = vgic_rank_offset(v, 64, gicd_reg - GICD_IROUTER,
          if ( rank == NULL ) goto write_ignore;
-        BUG_ON(v->domain->max_vcpus > 8);
+        BUG_ON(v->domain->max_vcpus > MAX_VIRT_CPUS);

This check is pointless. max_vcpus will always be inferior or equal to MAX_VIRT_CPUS.

          new_irouter = *r;
          vgic_lock_rank(v, rank, flags);

diff --git a/xen/include/asm-arm/config.h b/xen/include/asm-arm/config.h
index 3b23e05..817c216 100644
--- a/xen/include/asm-arm/config.h
+++ b/xen/include/asm-arm/config.h
@@ -47,7 +47,11 @@
  #define NR_CPUS 128

+#ifdef CONFIG_ARM_64
+#define MAX_VIRT_CPUS 128
  #define MAX_VIRT_CPUS 8

  #define asmlinkage /* Nothing needed */


Julien Grall

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