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Re: [PATCH v4 2/4] xen/arm: optimize the size of struct vcpu
- To: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: "Orzel, Michal" <michal.orzel@xxxxxxx>
- Date: Mon, 29 Dec 2025 12:08:34 +0100
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, "Volodymyr Babchuk" <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Delivery-date: Mon, 29 Dec 2025 11:08:54 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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.
>
> 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>
~Michal
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