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

[Wei Chen <Wei.Chen@xxxxxxx>]

> -----Original Message-----
> From: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Sent: 2021年9月25日 3:36
> To: Wei Chen <Wei.Chen@xxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>; xen-
> devel@xxxxxxxxxxxxxxxxxxxx; julien@xxxxxxx; Bertrand Marquis
> <Bertrand.Marquis@xxxxxxx>
> Subject: RE: [PATCH 23/37] xen/arm: implement node distance helpers for
> Arm
> 
> On Fri, 24 Sep 2021, Wei Chen wrote:
> > > -----Original Message-----
> > > From: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > > Sent: 2021年9月24日 9:47
> > > To: Wei Chen <Wei.Chen@xxxxxxx>
> > > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; sstabellini@xxxxxxxxxx;
> julien@xxxxxxx;
> > > Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
> > > Subject: Re: [PATCH 23/37] xen/arm: implement node distance helpers
> for
> > > Arm
> > >
> > > 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.
> > >
> >
> > srat stands for static resource affinity table, I think dtb also can be
> > treated as a static resource affinity table. So I keep SRAT in this
> patch
> > and other patches. I have seen your comment in patch#25. Before x86
> maintainers
> > give any feedback, can we still keep srat here?
> 
> Jan and I replied in the other thread. I think that in warning messages
> "SRAT" should not be mentioned when booting from DT. Ideally functions
> names and variables should be renamed too when shared between ACPI and
> DT but it is less critical, and it is fine if you don't do that in the
> next version.

Thanks. I'll leave it as it is, if I do not have a better name.