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Re: [Xen-devel] [PATCH] Avoid premature update of M2P in set_typed_p2m_entry

>>> On 06.06.14 at 00:55, <mukesh.rathor@xxxxxxxxxx> wrote:
> @@ -832,6 +827,11 @@ static int set_typed_p2m_entry(struct domain *d, 
> unsigned long gfn, mfn_t mfn,
>          gdprintk(XENLOG_ERR,
>                   "p2m_set_entry failed! mfn=%08lx rc:%d\n",
>                   mfn_x(get_gfn_query_unlocked(p2m->domain, gfn, &ot)), rc);
> +    else if ( p2m_is_ram(ot) )
> +    {
> +        ASSERT(mfn_valid(omfn));
> +        set_gpfn_from_mfn(mfn_x(omfn), INVALID_M2P_ENTRY);
> +    }

The only possible concern here is that all other code paths in p2m.c
do the M2P updates under lock. Tim - is that a requirement (formally
the M2P isn't really considered serialized by P2M locking I think)? Yet
then again, even if it isn't, the placement here might sooner or later
result in a Coverity warning (recognizing that all other paths do the
update with a lock held)...


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