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RE: [XEN PATCH v8 08/22] xen/arm: ffa: add support for FFA_ID_GET
- To: Julien Grall <julien@xxxxxxx>, Jens Wiklander <jens.wiklander@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Thu, 13 Apr 2023 12:40:13 +0000
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- Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Marc Bonnici <Marc.Bonnici@xxxxxxx>, Achin Gupta <Achin.Gupta@xxxxxxx>, Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
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- Thread-topic: [XEN PATCH v8 08/22] xen/arm: ffa: add support for FFA_ID_GET
Hi Julien,
> -----Original Message-----
> From: Julien Grall <julien@xxxxxxx>
> Subject: Re: [XEN PATCH v8 08/22] xen/arm: ffa: add support for FFA_ID_GET
> >> +static uint16_t get_vm_id(const struct domain *d)
> >> +{
> >> + /* +1 since 0 is reserved for the hypervisor in FF-A */
> >> + return d->domain_id + 1;
> >
> > Since here you want 0 to be reserved, I think maybe you can use
> > the "d->arch.p2m.vmid"? According to the logic in p2m_alloc_vmid(),
> > the "d->arch.p2m.vmid" is also a per-domain u16 value that starts
> > from 1.
>
> I would rather not do that for a few reasons:
> 1) This is assuming the P2M code is initialized first
> 2) We should not rely on the VMID to be fixed. We may need to change
> that if we want to run more VMs than the number of VMIDs (we may even
> need multiple VMIDs per domain...).
Yeah these arguments are reasonable. Forget about my comments then.
Kind regards,
Henry
>
> Cheers,
>
> --
> Julien Grall
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