Re: [PATCH v1 04/10] hw/arm: xenpvh: Add support for SMP guests

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 13/08/2024 6:02 pm, Edgar E. Iglesias wrote:
> On Mon, Aug 12, 2024 at 06:47:17PM -0700, Stefano Stabellini wrote:
>> On Mon, 12 Aug 2024, Edgar E. Iglesias wrote:
>>> From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>
>>>
>>> Add SMP support for Xen PVH ARM guests. Create max_cpus ioreq
>>> servers to handle hotplug.
>>>
>>> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
>>> ---
>>>  hw/arm/xen_arm.c | 5 +++--
>>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/hw/arm/xen_arm.c b/hw/arm/xen_arm.c
>>> index 5f75cc3779..ef8315969c 100644
>>> --- a/hw/arm/xen_arm.c
>>> +++ b/hw/arm/xen_arm.c
>>> @@ -173,7 +173,7 @@ static void xen_arm_init(MachineState *machine)
>>>  
>>>      xen_init_ram(machine);
>>>  
>>> -    xen_register_ioreq(xam->state, machine->smp.cpus, &xen_memory_listener);
>>> +    xen_register_ioreq(xam->state, machine->smp.max_cpus, &xen_memory_listener);
>>>  
>>>      xen_create_virtio_mmio_devices(xam);
>>>  
>>> @@ -218,7 +218,8 @@ static void xen_arm_machine_class_init(ObjectClass *oc, void *data)
>>>      MachineClass *mc = MACHINE_CLASS(oc);
>>>      mc->desc = "Xen PVH ARM machine";
>>>      mc->init = xen_arm_init;
>>> -    mc->max_cpus = 1;
>>> +    /* MAX number of vcpus supported by Xen.  */
>>> +    mc->max_cpus = GUEST_MAX_VCPUS;

The only suitable number here is the one you get back from XEN_DMOP_nr_vcpus

GUEST_MAX_VCPUS is and has always been bogus as a compile time constant
in the Xen public headers (yes, ARM inherited it from x86, but it should
have never been copied to start with).  Please do not introduce any
further uses of it.

~Andrew