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    SubjectRe: [PATCH v7 3/3] dax/kmem: allow kmem to add memory with memmap_on_memory
    Date
    Vishal Verma <vishal.l.verma@intel.com> writes:

    > Large amounts of memory managed by the kmem driver may come in via CXL,
    > and it is often desirable to have the memmap for this memory on the new
    > memory itself.
    >
    > Enroll kmem-managed memory for memmap_on_memory semantics if the dax
    > region originates via CXL. For non-CXL dax regions, retain the existing
    > default behavior of hot adding without memmap_on_memory semantics.
    >
    > Cc: Andrew Morton <akpm@linux-foundation.org>
    > Cc: David Hildenbrand <david@redhat.com>
    > Cc: Michal Hocko <mhocko@suse.com>
    > Cc: Oscar Salvador <osalvador@suse.de>
    > Cc: Dan Williams <dan.j.williams@intel.com>
    > Cc: Dave Jiang <dave.jiang@intel.com>
    > Cc: Dave Hansen <dave.hansen@linux.intel.com>
    > Cc: Huang Ying <ying.huang@intel.com>
    > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
    > Reviewed-by: David Hildenbrand <david@redhat.com>
    > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

    LGTM, Thanks!

    Reviewed-by: "Huang, Ying" <ying.huang@intel.com>

    > ---
    > drivers/dax/bus.h | 1 +
    > drivers/dax/dax-private.h | 1 +
    > drivers/dax/bus.c | 3 +++
    > drivers/dax/cxl.c | 1 +
    > drivers/dax/hmem/hmem.c | 1 +
    > drivers/dax/kmem.c | 8 +++++++-
    > drivers/dax/pmem.c | 1 +
    > 7 files changed, 15 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
    > index 1ccd23360124..cbbf64443098 100644
    > --- a/drivers/dax/bus.h
    > +++ b/drivers/dax/bus.h
    > @@ -23,6 +23,7 @@ struct dev_dax_data {
    > struct dev_pagemap *pgmap;
    > resource_size_t size;
    > int id;
    > + bool memmap_on_memory;
    > };
    >
    > struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data);
    > diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
    > index 27cf2daaaa79..446617b73aea 100644
    > --- a/drivers/dax/dax-private.h
    > +++ b/drivers/dax/dax-private.h
    > @@ -70,6 +70,7 @@ struct dev_dax {
    > struct ida ida;
    > struct device dev;
    > struct dev_pagemap *pgmap;
    > + bool memmap_on_memory;
    > int nr_range;
    > struct dev_dax_range {
    > unsigned long pgoff;
    > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
    > index 0ee96e6fc426..ad9f821b8c78 100644
    > --- a/drivers/dax/bus.c
    > +++ b/drivers/dax/bus.c
    > @@ -367,6 +367,7 @@ static ssize_t create_store(struct device *dev, struct device_attribute *attr,
    > .dax_region = dax_region,
    > .size = 0,
    > .id = -1,
    > + .memmap_on_memory = false,
    > };
    > struct dev_dax *dev_dax = devm_create_dev_dax(&data);
    >
    > @@ -1400,6 +1401,8 @@ struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
    > dev_dax->align = dax_region->align;
    > ida_init(&dev_dax->ida);
    >
    > + dev_dax->memmap_on_memory = data->memmap_on_memory;
    > +
    > inode = dax_inode(dax_dev);
    > dev->devt = inode->i_rdev;
    > dev->bus = &dax_bus_type;
    > diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c
    > index 8bc9d04034d6..c696837ab23c 100644
    > --- a/drivers/dax/cxl.c
    > +++ b/drivers/dax/cxl.c
    > @@ -26,6 +26,7 @@ static int cxl_dax_region_probe(struct device *dev)
    > .dax_region = dax_region,
    > .id = -1,
    > .size = range_len(&cxlr_dax->hpa_range),
    > + .memmap_on_memory = true,
    > };
    >
    > return PTR_ERR_OR_ZERO(devm_create_dev_dax(&data));
    > diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
    > index 5d2ddef0f8f5..b9da69f92697 100644
    > --- a/drivers/dax/hmem/hmem.c
    > +++ b/drivers/dax/hmem/hmem.c
    > @@ -36,6 +36,7 @@ static int dax_hmem_probe(struct platform_device *pdev)
    > .dax_region = dax_region,
    > .id = -1,
    > .size = region_idle ? 0 : range_len(&mri->range),
    > + .memmap_on_memory = false,
    > };
    >
    > return PTR_ERR_OR_ZERO(devm_create_dev_dax(&data));
    > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
    > index c57acb73e3db..0aa6c45a4e5a 100644
    > --- a/drivers/dax/kmem.c
    > +++ b/drivers/dax/kmem.c
    > @@ -12,6 +12,7 @@
    > #include <linux/mm.h>
    > #include <linux/mman.h>
    > #include <linux/memory-tiers.h>
    > +#include <linux/memory_hotplug.h>
    > #include "dax-private.h"
    > #include "bus.h"
    >
    > @@ -56,6 +57,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
    > unsigned long total_len = 0;
    > struct dax_kmem_data *data;
    > int i, rc, mapped = 0;
    > + mhp_t mhp_flags;
    > int numa_node;
    >
    > /*
    > @@ -136,12 +138,16 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
    > */
    > res->flags = IORESOURCE_SYSTEM_RAM;
    >
    > + mhp_flags = MHP_NID_IS_MGID;
    > + if (dev_dax->memmap_on_memory)
    > + mhp_flags |= MHP_MEMMAP_ON_MEMORY;
    > +
    > /*
    > * Ensure that future kexec'd kernels will not treat
    > * this as RAM automatically.
    > */
    > rc = add_memory_driver_managed(data->mgid, range.start,
    > - range_len(&range), kmem_name, MHP_NID_IS_MGID);
    > + range_len(&range), kmem_name, mhp_flags);
    >
    > if (rc) {
    > dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
    > diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
    > index ae0cb113a5d3..f3c6c67b8412 100644
    > --- a/drivers/dax/pmem.c
    > +++ b/drivers/dax/pmem.c
    > @@ -63,6 +63,7 @@ static struct dev_dax *__dax_pmem_probe(struct device *dev)
    > .id = id,
    > .pgmap = &pgmap,
    > .size = range_len(&range),
    > + .memmap_on_memory = false,
    > };
    >
    > return devm_create_dev_dax(&data);

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