Re: [PATCH v2 04/10] xen/arm: Keep memory nodes in device tree when Xen boots from EFI

[Stefano Stabellini <sstabellini@kernel.org>]

On Mon, 18 Apr 2022, Wei Chen wrote:
> In current code, when Xen is booting from EFI, it will delete
> all memory nodes in device tree. This would work well in current
> stage, because Xen can get memory map from EFI system table.
> However, EFI system table cannot completely replace memory nodes
> of device tree. EFI system table doesn't contain memory NUMA
> information. Xen depends on ACPI SRAT or device tree memory nodes
> to parse memory blocks' NUMA mapping. So in EFI + DTB boot, Xen
> doesn't have any method to get numa-node-id for memory blocks any
> more. This makes device tree based NUMA support become impossible
> for Xen in EFI + DTB boot.
> 
> So in this patch, we will keep memory nodes in device tree for
> NUMA code to parse memory numa-node-id later.
> 
> As a side effect, if we still parse boot memory information in
> early_scan_node, bootmem.info will calculate memory ranges in
> memory nodes twice. So we have to prevent early_scan_node to
> parse memory nodes in EFI boot.
> 
> Signed-off-by: Wei Chen <wei.chen@arm.com>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
> v1 -> v2:
> 1. Move this patch from later to early of this series.
> 2. Refine commit message.
> ---
>  xen/arch/arm/bootfdt.c      |  8 +++++++-
>  xen/arch/arm/efi/efi-boot.h | 25 -------------------------
>  2 files changed, 7 insertions(+), 26 deletions(-)
> 
> diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
> index e318ef9603..78e10c6ebc 100644
> --- a/xen/arch/arm/bootfdt.c
> +++ b/xen/arch/arm/bootfdt.c
> @@ -11,6 +11,7 @@
>  #include <xen/lib.h>
>  #include <xen/kernel.h>
>  #include <xen/init.h>
> +#include <xen/efi.h>
>  #include <xen/device_tree.h>
>  #include <xen/libfdt/libfdt.h>
>  #include <xen/sort.h>
> @@ -370,7 +371,12 @@ static int __init early_scan_node(const void *fdt,
>  {
>      int rc = 0;
>  
> -    if ( device_tree_node_matches(fdt, node, "memory") )
> +    /*
> +     * If Xen has been booted via UEFI, the memory banks are
> +     * populated. So we should skip the parsing.
> +     */
> +    if ( !efi_enabled(EFI_BOOT) &&
> +         device_tree_node_matches(fdt, node, "memory") )
>          rc = process_memory_node(fdt, node, name, depth,
>                                   address_cells, size_cells, &bootinfo.mem);
>      else if ( depth == 1 && !dt_node_cmp(name, "reserved-memory") )
> diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
> index e452b687d8..59d93c24a1 100644
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -231,33 +231,8 @@ EFI_STATUS __init fdt_add_uefi_nodes(EFI_SYSTEM_TABLE *sys_table,
>      int status;
>      u32 fdt_val32;
>      u64 fdt_val64;
> -    int prev;
>      int num_rsv;
>  
> -    /*
> -     * Delete any memory nodes present.  The EFI memory map is the only
> -     * memory description provided to Xen.
> -     */
> -    prev = 0;
> -    for (;;)
> -    {
> -        const char *type;
> -        int len;
> -
> -        node = fdt_next_node(fdt, prev, NULL);
> -        if ( node < 0 )
> -            break;
> -
> -        type = fdt_getprop(fdt, node, "device_type", &len);
> -        if ( type && strncmp(type, "memory", len) == 0 )
> -        {
> -            fdt_del_node(fdt, node);
> -            continue;
> -        }
> -
> -        prev = node;
> -    }
> -
>     /*
>      * Delete all memory reserve map entries. When booting via UEFI,
>      * kernel will use the UEFI memory map to find reserved regions.
> -- 
> 2.25.1
>