Re: [PATCH v4 2/4] xen/arm: optimize the size of struct vcpu

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 12/29/25 12:08 PM, Orzel, Michal wrote:
> On 23/12/2025 18:01, Oleksii Kurochko wrote:
> > When CONFIG_NEW_VGIC=y and CONFIG_ARM_64=y, the size of struct vcpu
> > exceeds one page, which requires allocating two pages and led to the
> > introduction of MAX_PAGES_PER_VCPU.
> >
> > To remove the need for MAX_PAGES_PER_VCPU in a follow-up patch, the vgic
> > member of NEW_VGIC's struct vgic_vcpu member private_irq is changed to a
> s/vgic_vcpu/vgic_cpu/
> s/private_irq/private_irqs/
>
> > pointer to struct vgic_irq.
> > As a result, the size of struct vcpu for Arm64 is reduced to 2176 bytes,
> > compared to 3840 bytes (without these changes and with CONFIG_ARM_64=y)
> > and 4736 bytes (without these changes and with both CONFIG_ARM_64=y and
> > CONFIG_NEW_VGIC=y).
> You only touch new vGIC, so there should be no size reduction without it but the
> paragraph reads as if the change affected both old and new vGIC. Also I would
> mention that probably you provided the numbers based on a defconfig target.
  Yes, all the numbers are provided based on defconfig target.
  I will update this paragraph in the following way to be more clear:
  As a result, the size of struct vcpu for Arm64 is reduced to 2176 bytes
  in the case when CONFIG_ARM_64=y and CONFIG_NEW_VGIC=y, compared to 3840
  bytes (without these changes and with CONFIG_ARM_64=y) and 4736 bytes
  (without these changes and with both CONFIG_ARM_64=y and CONFIG_NEW_VGIC=y).
  Note that all numbers are based on defconfig with the mentioned options
  enabled or disabled as specified.

> > Since the private_irqs member is now a pointer, vcpu_vgic_init() and
> > vcpu_vgic_free() are updated to allocate and free private_irqs instance.
> >
> > Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> > Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Other than that:
> Acked-by: Michal Orzel <michal.orzel@xxxxxxx>
Thanks!

~ Oleksii