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Re: [PATCH v5 1/3] xen/arm: optimize the size of struct vcpu
- To: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: "Orzel, Michal" <michal.orzel@xxxxxxx>
- Date: Fri, 9 Jan 2026 14:15:12 +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: Fri, 09 Jan 2026 13:15:30 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 07/01/2026 17:28, 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, the vgic member of NEW_VGIC's
> struct vgic_cpu member private_irqs is changed to a pointer to struct
> vgic_irq.
> 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.
>
> As struct vcpu now fits into one page, drop MAX_PAGES_PER_VCPU.
>
> Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> Michal gave his:
> Acked-by: Michal Orzel <michal.orzel@xxxxxxx>
> But wrote to MAX_PAGES_PER_VCPU in this patch, so probably he would
> like to look at how it was done.
Looks ok, you can retain the tag.
~MichaL
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