On 28/08/2024 20:24, Julien Grall wrote:
Hi Ayan,
Hi Julien,

The title is a bit confusing. It implies seconary CPU bringup used to work on the MPU. However, you are adding a stub for enable_secondary_cpu_mm.

Also, I am not entirely this is really sufficient to disable CPU bringup. There will be plenty of initialization done for secondary CPUs.
I agree. init_secondary() has already been invoked before this.

I would suggest to update NR_CPUS to 1 for MPU so we will fail early.
Yes, I will do this.

For the title, how about

xen/arm: mpu: Implement a dummy enable_secondary_cpu_mm

On 23/08/2024 17:31, Ayan Kumar Halder wrote:
Secondary cpus are put in WFE state. We do not support SMP at this time.

Signed-off-by: Ayan Kumar Halder <ayan.kumar.hal...@amd.com>
---
  xen/arch/arm/arm64/mpu/head.S | 9 +++++++++
  1 file changed, 9 insertions(+)

diff --git a/xen/arch/arm/arm64/mpu/head.S b/xen/arch/arm/arm64/mpu/head.S
index 2b023c346a..1579ac0408 100644
--- a/xen/arch/arm/arm64/mpu/head.S
+++ b/xen/arch/arm/arm64/mpu/head.S
@@ -68,3 +68,12 @@ ENTRY(enable_boot_cpu_mm)
        ret
  ENDPROC(enable_boot_cpu_mm)
+
+/*
+ * Secondary cpu has not yet been supported on MPU systems. We will block the
+ * secondary cpu bringup at this stage.
+ */
+ENTRY(enable_secondary_cpu_mm)

Can we print a message so it is easier to spot that enable_secondary_cpu_mm is not properly implemented?

yes, something like this

PRINT("- SMP NOT SUPPORTED -\r\n")

- Ayan


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