Re: [PATCH v2 2/6] arm/mpu: Implement vmap functions for MPU

["Orzel, Michal" <michal.orzel@xxxxxxx>]

Also, two more things here apart from my other remarks.

On 05/01/2026 12:34, Harry Ramsey wrote:
> From: Luca Fancellu <luca.fancellu@xxxxxxx>
> 
> HAS_VMAP is not enabled on MPU systems, but the vmap functions are used
> in places across common code. In order to keep the existing code and
> maintain correct functionality, implement the `vmap_contig` and `vunmap`
> functions for MPU systems.
> 
> Introduce a helper function `destroy_xen_mapping_containing` to aid with
> unmapping an entire region when only the start address is known.
> 
> Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
> Signed-off-by: Harry Ramsey <harry.ramsey@xxxxxxx>
> ---
> v2:
> - Rename `destroy_entire_xen_mapping` to `destroy_xen_mapping_containing`
> - Improve code documentation.
> - Refactor nested code.
> - Fix ignored rc error code in `destroy_xen_mapping_containing`.
> ---
...
>  
> +int destroy_xen_mapping_containing(paddr_t s)
> +{
> +    int rc;
> +    uint8_t idx;
> +
> +    ASSERT(IS_ALIGNED(s, PAGE_SIZE));
> +
> +    spin_lock(&xen_mpumap_lock);
Here you take a lock...

> +
> +    rc = mpumap_contains_region(xen_mpumap, max_mpu_regions, s, s + 
> PAGE_SIZE,
> +                                &idx);
> +    if ( rc == MPUMAP_REGION_NOTFOUND )
> +    {
> +        printk(XENLOG_ERR "Cannot remove entry that does not exist");
> +        return -EINVAL;
and here you would return while still holding the lock i.e. deadlock.

> +    }
> +
> +    /* As we are unmapping entire region use MPUMAP_REGION_FOUND instead */
> +    rc = xen_mpumap_free_entry(idx, MPUMAP_REGION_FOUND);
Why don't you perform context_sync_mpu() here?

~Michal