Re: [PATCH 23/37] xen/arm: implement node distance helpers for Arm

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 23 Sep 2021, Wei Chen wrote:
> We will parse NUMA nodes distances from device tree or ACPI
> table. So we need a matrix to record the distances between
> any two nodes we parsed. Accordingly, we provide this
> node_set_distance API for device tree or ACPI table parsers
> to set the distance for any two nodes in this patch.
> When NUMA initialization failed, __node_distance will return
> NUMA_REMOTE_DISTANCE, this will help us avoid doing rollback
> for distance maxtrix when NUMA initialization failed.
> 
> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> ---
>  xen/arch/arm/Makefile      |  1 +
>  xen/arch/arm/numa.c        | 69 ++++++++++++++++++++++++++++++++++++++
>  xen/include/asm-arm/numa.h | 13 +++++++
>  3 files changed, 83 insertions(+)
>  create mode 100644 xen/arch/arm/numa.c
> 
> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
> index ae4efbf76e..41ca311b6b 100644
> --- a/xen/arch/arm/Makefile
> +++ b/xen/arch/arm/Makefile
> @@ -35,6 +35,7 @@ obj-$(CONFIG_LIVEPATCH) += livepatch.o
>  obj-y += mem_access.o
>  obj-y += mm.o
>  obj-y += monitor.o
> +obj-$(CONFIG_NUMA) += numa.o
>  obj-y += p2m.o
>  obj-y += percpu.o
>  obj-y += platform.o
> diff --git a/xen/arch/arm/numa.c b/xen/arch/arm/numa.c
> new file mode 100644
> index 0000000000..3f08870d69
> --- /dev/null
> +++ b/xen/arch/arm/numa.c
> @@ -0,0 +1,69 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Arm Architecture support layer for NUMA.
> + *
> + * Copyright (C) 2021 Arm Ltd
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + *
> + */
> +#include <xen/init.h>
> +#include <xen/numa.h>
> +
> +static uint8_t __read_mostly
> +node_distance_map[MAX_NUMNODES][MAX_NUMNODES] = {
> +    { 0 }
> +};
> +
> +void __init numa_set_distance(nodeid_t from, nodeid_t to, uint32_t distance)
> +{
> +    if ( from >= MAX_NUMNODES || to >= MAX_NUMNODES )
> +    {
> +        printk(KERN_WARNING
> +               "NUMA: invalid nodes: from=%"PRIu8" to=%"PRIu8" 
> MAX=%"PRIu8"\n",
> +               from, to, MAX_NUMNODES);
> +        return;
> +    }
> +
> +    /* NUMA defines 0xff as an unreachable node and 0-9 are undefined */
> +    if ( distance >= NUMA_NO_DISTANCE ||
> +        (distance >= NUMA_DISTANCE_UDF_MIN &&
> +         distance <= NUMA_DISTANCE_UDF_MAX) ||
> +        (from == to && distance != NUMA_LOCAL_DISTANCE) )
> +    {
> +        printk(KERN_WARNING
> +               "NUMA: invalid distance: from=%"PRIu8" to=%"PRIu8" 
> distance=%"PRIu32"\n",
> +               from, to, distance);
> +        return;
> +    }
> +
> +    node_distance_map[from][to] = distance;
> +}
> +
> +uint8_t __node_distance(nodeid_t from, nodeid_t to)
> +{
> +    /* When NUMA is off, any distance will be treated as remote. */
> +    if ( srat_disabled() )

Given that this is ARM specific code and specific to ACPI, I don't think
we should have any call to something called "srat_disabled".

I suggest to either rename srat_disabled to numa_distance_disabled.

Other than that, this patch looks OK to me.


> +        return NUMA_REMOTE_DISTANCE;
> +
> +    /*
> +     * Check whether the nodes are in the matrix range.
> +     * When any node is out of range, except from and to nodes are the
> +     * same, we treat them as unreachable (return 0xFF)
> +     */
> +    if ( from >= MAX_NUMNODES || to >= MAX_NUMNODES )
> +        return from == to ? NUMA_LOCAL_DISTANCE : NUMA_NO_DISTANCE;
> +
> +    return node_distance_map[from][to];
> +}
> +EXPORT_SYMBOL(__node_distance);
> diff --git a/xen/include/asm-arm/numa.h b/xen/include/asm-arm/numa.h
> index 21569e634b..758eafeb05 100644
> --- a/xen/include/asm-arm/numa.h
> +++ b/xen/include/asm-arm/numa.h
> @@ -9,8 +9,21 @@ typedef u8 nodeid_t;
>  
>  #ifdef CONFIG_NUMA
>  
> +/*
> + * In ACPI spec, 0-9 are the reserved values for node distance,
> + * 10 indicates local node distance, 20 indicates remote node
> + * distance. Set node distance map in device tree will follow
> + * the ACPI's definition.
> + */
> +#define NUMA_DISTANCE_UDF_MIN   0
> +#define NUMA_DISTANCE_UDF_MAX   9
> +#define NUMA_LOCAL_DISTANCE     10
> +#define NUMA_REMOTE_DISTANCE    20
> +
>  #define NR_NODE_MEMBLKS NR_MEM_BANKS
>  
> +extern void numa_set_distance(nodeid_t from, nodeid_t to, uint32_t distance);
> +
>  #else
>  
>  /* Fake one node for now. See also node_online_map. */
> -- 
> 2.25.1
>