Re: [Xen-devel] [PATCH 14/18] arm/altp2m: Add HVMOP_altp2m_set_mem_access.

[Julien Grall <julien.grall@xxxxxxx>]

Hello Sergej,

On 04/07/16 12:45, Sergej Proskurin wrote:
> +static inline
> +int p2m_set_altp2m_mem_access(struct domain *d, struct p2m_domain *hp2m,
> +                              struct p2m_domain *ap2m, p2m_access_t a,
> +                              gfn_t gfn)
> +{
[...]

> +    /* Set mem access attributes - currently supporting only one (4K) page. */
> +    mask = level_masks[3];
> +    return apply_p2m_changes(d, ap2m, INSERT,
> +                             gpa & mask,
> +                             (gpa + level_sizes[level]) & mask,
> +                             maddr & mask, mattr, 0, p2mt, a);
The operation INSERT will remove the previous mapping and decrease page 
reference for foreign mapping (see p2m_put_l3_page). So if you set the 
memory access for this kind of page, the reference count will be wrong 
afterward.
--
Julien Grall

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