[PATCH 1/2] libnvdimm, pmem: fix 'pfn' support for section-misaligned namespaces

[Dan Williams]

The altmap for a section-misaligned namespace needs to arrange for the
base_pfn to be section-aligned.  As a result the 'reserve' region (pfns
from base that do not have a struct page) must be increased.  Otherwise
we trip the altmap validation check in __add_pages:

        if (altmap->base_pfn != phys_start_pfn
                        || vmem_altmap_offset(altmap) > nr_pages) {
                pr_warn_once("memory add fail, invalid altmap\n");
                return -EINVAL;
        }

Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 drivers/nvdimm/pmem.c |   29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index efc2a5e671c6..6a6283ab974c 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -356,6 +356,31 @@ static int nvdimm_namespace_detach_pfn(struct 
nd_namespace_common *ndns)
        return 0;
 }
 
+/*
+ * We hotplug memory at section granularity, pad the reserved area from
+ * the previous section base to the namespace base address.
+ */
+static unsigned long init_altmap_base(resource_size_t base)
+{
+       unsigned long base_pfn = __phys_to_pfn(base);
+
+#ifdef CONFIG_SPARSEMEM
+       base_pfn = SECTION_ALIGN_DOWN(base_pfn);
+#endif
+       return base_pfn;
+}
+
+static unsigned long init_altmap_reserve(resource_size_t base)
+{
+       unsigned long base_pfn = __phys_to_pfn(base);
+       unsigned long reserve = __phys_to_pfn(SZ_8K);
+
+#ifdef CONFIG_SPARSEMEM
+       reserve += base_pfn - SECTION_ALIGN_DOWN(base_pfn);
+#endif
+       return reserve;
+}
+
 static int nvdimm_namespace_attach_pfn(struct nd_namespace_common *ndns)
 {
        struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
@@ -369,8 +394,8 @@ static int nvdimm_namespace_attach_pfn(struct 
nd_namespace_common *ndns)
        phys_addr_t offset;
        int rc;
        struct vmem_altmap __altmap = {
-               .base_pfn = __phys_to_pfn(nsio->res.start),
-               .reserve = __phys_to_pfn(SZ_8K),
+               .base_pfn = init_altmap_base(nsio->res.start),
+               .reserve = init_altmap_reserve(nsio->res.start),
        };
 
        if (!nd_pfn->uuid || !nd_pfn->ndns)