Re: [Xen-devel] [PATCH v10 18/32] ARM: vITS: introduce translation table walks

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 26/05/17 18:35, Andre Przywara wrote:
> +/*
> + * Queries the collection and device tables to translate the device ID and
> + * event ID and find the appropriate ITTE. The given collection ID and the
> + * virtual LPI number are then stored into that entry.
> + * If vcpu_ptr is provided, returns the VCPU belonging to that collection.
> + * Must be called with the ITS lock held.
> + */
> +bool write_itte_locked(struct virt_its *its, uint32_t devid,
> +                       uint32_t evid, uint32_t collid, uint32_t vlpi,
> +                       struct vcpu **vcpu_ptr)
> +{
> +    paddr_t addr;
> +    struct vits_itte itte;
> +
> +    ASSERT(spin_is_locked(&its->its_lock));
> +
> +    if ( collid >= its->max_collections )
> +        return false;
This check will always fail with the command DISCARD because collid == 
UNMAPPED_COLLECTION (~0).
Looking at the code, I am not sure why you need to validate collid and 
nr_lpis in write_itte_locked. This should have been made by the caller.
> +
> +    if ( vlpi >= its->d->arch.vgic.nr_lpis )
> +        return false;
> +
> +    addr = its_get_itte_address(its, devid, evid);
> +    if ( addr == INVALID_PADDR )
> +        return false;
> +
> +    itte.collection = collid;
> +    itte.vlpi = vlpi;
> +
> +    if ( vgic_access_guest_memory(its->d, addr, &itte, sizeof(itte), true) )
> +        return false;
> +
> +    if ( vcpu_ptr )
> +        *vcpu_ptr = get_vcpu_from_collection(its, collid);
I guess this is why you check the collection in this function. However, 
I am not sure how this is related to write_itte_locked.
Cheers,

--
Julien Grall

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