Re: [PATCH 17/22] x86/setup: vmap heap nodes when they are outside the direct map

[Stefano Stabellini <sstabellini@kernel.org>]

On Fri, 16 Dec 2022, Julien Grall wrote:
> From: Hongyan Xia <hongyxia@amazon.com>
> 
> When we do not have a direct map, archs_mfn_in_direct_map() will always
> return false, thus init_node_heap() will allocate xenheap pages from an
> existing node for the metadata of a new node. This means that the
> metadata of a new node is in a different node, slowing down heap
> allocation.
> 
> Since we now have early vmap, vmap the metadata locally in the new node.
> 
> Signed-off-by: Hongyan Xia <hongyxia@amazon.com>
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> 
> ----
> 
>     Changes from Hongyan's version:
>         * arch_mfn_in_direct_map() was renamed to
>           arch_mfns_in_direct_map()
>         * Use vmap_contig_pages() rather than __vmap(...).
>         * Add missing include (xen/vmap.h) so it compiles on Arm
> ---
>  xen/common/page_alloc.c | 42 +++++++++++++++++++++++++++++++----------
>  1 file changed, 32 insertions(+), 10 deletions(-)
> 
> diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
> index 0c4af5a71407..581c15d74dfb 100644
> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -136,6 +136,7 @@
>  #include <xen/sched.h>
>  #include <xen/softirq.h>
>  #include <xen/spinlock.h>
> +#include <xen/vmap.h>
>  
>  #include <asm/flushtlb.h>
>  #include <asm/numa.h>
> @@ -597,22 +598,43 @@ static unsigned long init_node_heap(int node, unsigned long mfn,
>          needed = 0;
>      }
>      else if ( *use_tail && nr >= needed &&
> -              arch_mfns_in_directmap(mfn + nr - needed, needed) &&
>                (!xenheap_bits ||
>                 !((mfn + nr - 1) >> (xenheap_bits - PAGE_SHIFT))) )
>      {
> -        _heap[node] = mfn_to_virt(mfn + nr - needed);
> -        avail[node] = mfn_to_virt(mfn + nr - 1) +
> -                      PAGE_SIZE - sizeof(**avail) * NR_ZONES;
> -    }
> -    else if ( nr >= needed &&
> -              arch_mfns_in_directmap(mfn, needed) &&
> +        if ( arch_mfns_in_directmap(mfn + nr - needed, needed) )
> +        {
> +            _heap[node] = mfn_to_virt(mfn + nr - needed);
> +            avail[node] = mfn_to_virt(mfn + nr - 1) +
> +                          PAGE_SIZE - sizeof(**avail) * NR_ZONES;
> +        }
> +        else
> +        {
> +            mfn_t needed_start = _mfn(mfn + nr - needed);
> +
> +            _heap[node] = vmap_contig_pages(needed_start, needed);
> +            BUG_ON(!_heap[node]);

I see a BUG_ON here but init_node_heap is not __init. Asking because
BUG_ON is only a good idea during init time. Should init_node_heap be
__init (not necessarely in this patch, but still)?


> +            avail[node] = (void *)(_heap[node]) + (needed << PAGE_SHIFT) -
> +                          sizeof(**avail) * NR_ZONES;
> +        }
> +    } else if ( nr >= needed &&
>                (!xenheap_bits ||
>                 !((mfn + needed - 1) >> (xenheap_bits - PAGE_SHIFT))) )
>      {
> -        _heap[node] = mfn_to_virt(mfn);
> -        avail[node] = mfn_to_virt(mfn + needed - 1) +
> -                      PAGE_SIZE - sizeof(**avail) * NR_ZONES;
> +        if ( arch_mfns_in_directmap(mfn, needed) )
> +        {
> +            _heap[node] = mfn_to_virt(mfn);
> +            avail[node] = mfn_to_virt(mfn + needed - 1) +
> +                          PAGE_SIZE - sizeof(**avail) * NR_ZONES;
> +        }
> +        else
> +        {
> +            mfn_t needed_start = _mfn(mfn);
> +
> +            _heap[node] = vmap_contig_pages(needed_start, needed);
> +            BUG_ON(!_heap[node]);
> +            avail[node] = (void *)(_heap[node]) + (needed << PAGE_SHIFT) -
> +                          sizeof(**avail) * NR_ZONES;
> +        }
>          *use_tail = false;
>      }
>      else if ( get_order_from_bytes(sizeof(**_heap)) ==
> -- 
> 2.38.1
>