On Tue, Mar 24, 2020 at 12:41 PM Joao Martins <joao.m.martins@xxxxxxxxxx> wrote:
>
> On 3/22/20 4:12 PM, Dan Williams wrote:
> > The hmem enabling in commit 'cf8741ac57ed ("ACPI: NUMA: HMAT: Register
> > "soft reserved" memory as an "hmem" device")' only registered ranges to
> > the hmem driver for each soft-reservation that also appeared in the
> > HMAT. While this is meant to encourage platform firmware to "do the
> > right thing" and publish an HMAT, the corollary is that platforms that
> > fail to publish an accurate HMAT will strand memory from Linux usage.
> > Additionally, the "efi_fake_mem" kernel command line option enabling
> > will strand memory by default without an HMAT.
> >
> > Arrange for "soft reserved" memory that goes unclaimed by HMAT entries
> > to be published as raw resource ranges for the hmem driver to consume.
> >
> > Include a module parameter to disable either this fallback behavior, or
> > the hmat enabling from creating hmem devices. The module parameter
> > requires the hmem device enabling to have unique name in the module
> > namespace: "device_hmem".
> >
> > Rather than mark this x86-only, include an interim phys_to_target_node()
> > implementation for arm64.
> >
> > Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> > Cc: Brice Goglin <Brice.Goglin@xxxxxxxx>
> > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> > Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> > Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Will Deacon <will@xxxxxxxxxx>
> > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> > ---
> > arch/arm64/mm/numa.c | 13 +++++++++++++
> > drivers/dax/Kconfig | 1 +
> > drivers/dax/hmem/Makefile | 3 ++-
> > drivers/dax/hmem/device.c | 33 +++++++++++++++++++++++++++++++++
> > 4 files changed, 49 insertions(+), 1 deletion(-)
> >
>
> [...]
>
> > diff --git a/drivers/dax/hmem/device.c b/drivers/dax/hmem/device.c
> > index 99bc15a8b031..f9c5fa8b1880 100644
> > --- a/drivers/dax/hmem/device.c
> > +++ b/drivers/dax/hmem/device.c
> > @@ -4,6 +4,9 @@
> > #include <linux/module.h>
> > #include <linux/mm.h>
> >
> > +static bool nohmem;
> > +module_param_named(disable, nohmem, bool, 0444);
> > +
> > void hmem_register_device(int target_nid, struct resource *r)
> > {
> > /* define a clean / non-busy resource for the platform device */
> > @@ -16,6 +19,9 @@ void hmem_register_device(int target_nid, struct resource *r)
> > struct memregion_info info;
> > int rc, id;
> >
> > + if (nohmem)
> > + return;
> > +
> > rc = region_intersects(res.start, resource_size(&res), IORESOURCE_MEM,
> > IORES_DESC_SOFT_RESERVED);
> > if (rc != REGION_INTERSECTS)
> > @@ -62,3 +68,30 @@ void hmem_register_device(int target_nid, struct resource *r)
> > out_pdev:
> > memregion_free(id);
> > }
> > +
> > +static __init int hmem_register_one(struct resource *res, void *data)
> > +{
> > + /*
> > + * If the resource is not a top-level resource it was already
> > + * assigned to a device by the HMAT parsing.
> > + */
> > + if (res->parent != &iomem_resource)
> > + return 0;
> > +
> > + hmem_register_device(phys_to_target_node(res->start), res);
> > +
> > + return 0;
>
> Should we add an error returning value to hmem_register_device() perhaps this
> ought to be reflected in hmem_register_one().
>
> > +}
> > +
> > +static __init int hmem_init(void)
> > +{
> > + walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED,
> > + IORESOURCE_MEM, 0, -1, NULL, hmem_register_one);
> > + return 0;
> > +}
> > +
>
> (...) and then perhaps here returning in the initcall if any of the resources
> failed hmem registration?
Except that hmem_register_one() is a stop-gap to collect soft-reserved
ranges that were not already registered, and it's not an error to find
already registered devices. However, I do think it's a good idea to
log registrations that failed for other reasons.
