Re: [PATCH v5 7/9] xen/arm: unpopulate memory when domain is static

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 31 May 2022, Penny Zheng wrote:
> Today when a domain unpopulates the memory on runtime, they will always
> hand the memory back to the heap allocator. And it will be a problem if domain
> is static.
> 
> Pages as guest RAM for static domain shall be reserved to only this domain
> and not be used for any other purposes, so they shall never go back to heap
> allocator.
> 
> This commit puts reserved pages on the new list resv_page_list only after
> having taken them off the "normal" list, when the last ref dropped.
> 
> Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>

ARM bits:
Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
> v5 changes:
> - adapt this patch for PGC_staticmem
> ---
> v4 changes:
> - no changes
> ---
> v3 changes:
> - have page_list_del() just once out of the if()
> - remove resv_pages counter
> - make arch_free_heap_page be an expression, not a compound statement.
> ---
> v2 changes:
> - put reserved pages on resv_page_list after having taken them off
> the "normal" list
> ---
>  xen/arch/arm/include/asm/mm.h | 12 ++++++++++++
>  xen/common/domain.c           |  4 ++++
>  xen/include/xen/sched.h       |  3 +++
>  3 files changed, 19 insertions(+)
> 
> diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h
> index 56d0939318..ca384a3939 100644
> --- a/xen/arch/arm/include/asm/mm.h
> +++ b/xen/arch/arm/include/asm/mm.h
> @@ -360,6 +360,18 @@ void clear_and_clean_page(struct page_info *page);
>  
>  unsigned int arch_get_dma_bitsize(void);
>  
> +/*
> + * Put free pages on the resv page list after having taken them
> + * off the "normal" page list, when pages from static memory
> + */
> +#ifdef CONFIG_STATIC_MEMORY
> +#define arch_free_heap_page(d, pg) ({                   \
> +    page_list_del(pg, page_to_list(d, pg));             \
> +    if ( (pg)->count_info & PGC_staticmem )              \
> +        page_list_add_tail(pg, &(d)->resv_page_list);   \
> +})
> +#endif
> +
>  #endif /*  __ARCH_ARM_MM__ */
>  /*
>   * Local variables:
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index a3ef991bd1..a49574fa24 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -604,6 +604,10 @@ struct domain *domain_create(domid_t domid,
>      INIT_PAGE_LIST_HEAD(&d->page_list);
>      INIT_PAGE_LIST_HEAD(&d->extra_page_list);
>      INIT_PAGE_LIST_HEAD(&d->xenpage_list);
> +#ifdef CONFIG_STATIC_MEMORY
> +    INIT_PAGE_LIST_HEAD(&d->resv_page_list);
> +#endif
> +
>  
>      spin_lock_init(&d->node_affinity_lock);
>      d->node_affinity = NODE_MASK_ALL;
> diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
> index 5191853c18..3e22c77333 100644
> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -381,6 +381,9 @@ struct domain
>      struct page_list_head page_list;  /* linked list */
>      struct page_list_head extra_page_list; /* linked list (size extra_pages) 
> */
>      struct page_list_head xenpage_list; /* linked list (size xenheap_pages) 
> */
> +#ifdef CONFIG_STATIC_MEMORY
> +    struct page_list_head resv_page_list; /* linked list (size resv_pages) */
> +#endif
>  
>      /*
>       * This field should only be directly accessed by 
> domain_adjust_tot_pages()
> -- 
> 2.25.1
>