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Re: [PATCH v4 3/4] xen/arm: vgic: free eSPIs using the bitmap index
- To: "Orzel, Michal" <michal.orzel@xxxxxxx>
- From: Mykola Kvach <mykola_kvach@xxxxxxxx>
- Date: Wed, 23 Sep 2026 12:09:54 +0300
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Wed, 23 Sep 2026 09:10:09 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Mail-followup-to: "Orzel, Michal" <michal.orzel@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
On Tue, Sep 22, 2026 at 04:21:13PM +0200, Orzel, Michal wrote:
>
>
> On 22-Sep-26 08:39, Mykola Kvach wrote:
> > The allocated_irqs bitmap in the existing vGIC implementation stores eSPI
> > allocation bits immediately after the regular vIRQ bits.
> > vgic_reserve_virq() converts an eSPI INTID to this compressed bitmap index,
> > but vgic_free_virq() used the raw INTID.
> >
> > Freeing INTID 4096 therefore clears bit 4096 instead of the first eSPI bit.
> > This writes beyond allocated_irqs and leaves the intended eSPI bit set.
> > Valid eSPIs reach this path during DOMCTL bind failure cleanup and unbind,
> > and during vPL011 teardown.
> >
> > Add virq_to_idx(), the inverse of idx_to_virq(), and use it when reserving
> > and freeing vIRQs. Validate a vIRQ before clearing its allocation bit.
> Please also add this validation (just vgic_is_valid_line() guard) to a new
> VGIC
> vgic.c. It's eSPI agnostic and we should keep them in sync if possible.
Sure, I can add the validation there as well.
Just to clarify, NEW_VGIC currently selects GICV2 and GICV3_ESPI
depends on GICV3 && !NEW_VGIC, so the eSPI bitmap issue itself cannot
affect the new VGIC. But I agree that the validity check is generic and
it makes sense to keep vgic_free_virq() consistent between the two
implementations.
Best regards,
Mykola
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