On 10.06.2025 15:05, Oleksii Kurochko wrote:
> @@ -113,3 +117,58 @@ int p2m_init(struct domain *d)
>
> return 0;
> }
> +
> +/*
> + * Set the pool of pages to the required number of pages.
> + * Returns 0 for success, non-zero for failure.
> + * Call with d->arch.paging.lock held.
> + */
> +int p2m_set_allocation(struct domain *d, unsigned long pages, bool
> *preempted)
> +{
> + struct page_info *pg;
> +
> + ASSERT(spin_is_locked(&d->arch.paging.lock));
> +
> + for ( ; ; )
> + {
> + if ( d->arch.paging.p2m_total_pages < pages )
> + {
> + /* Need to allocate more memory from domheap */
> + pg = alloc_domheap_page(d, MEMF_no_owner);
> + if ( pg == NULL )
> + {
> + printk(XENLOG_ERR "Failed to allocate P2M pages.\n");
> + return -ENOMEM;
> + }
> + ACCESS_ONCE(d->arch.paging.p2m_total_pages)++;
> + page_list_add_tail(pg, &d->arch.paging.p2m_freelist);
> + }
> + else if ( d->arch.paging.p2m_total_pages > pages )
> + {
> + /* Need to return memory to domheap */
> + pg = page_list_remove_head(&d->arch.paging.p2m_freelist);
> + if( pg )
> + {
> + ACCESS_ONCE(d->arch.paging.p2m_total_pages)--;
> + free_domheap_page(pg);
> + }
> + else
> + {
> + printk(XENLOG_ERR
> + "Failed to free P2M pages, P2M freelist is empty.\n");
> + return -ENOMEM;
> + }
> + }
> + else
> + break;
> +
> + /* Check to see if we need to yield and try again */
> + if ( preempted && general_preempt_check() )
> + {
> + *preempted = true;
> + return -ERESTART;
> + }
> + }
> +
> + return 0;
> +}
Btw, with the order-2 requirement for the root page table, you may want to
consider an alternative approach: Here you could allocate some order-2
pages (possibly up to as many as a domain might need, which right now
would be exactly one), put them on a separate list, and consume the root
table(s) from there. If you run out of pages on the order-0 list, you
could shatter a page from the order-2 one (as long as that's still non-
empty). The difficulty would be with freeing, where a previously shattered
order-2 page would be nice to re-combine once all of its constituents are
free again. The main benefit would be avoiding the back and forth in patch
6.
Jan
