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SubjectRe: [PATCH 2/2] libnvdimm, pfn: Pad pfn namespaces relative to other regions
Date

On Sat, 2018-11-24 at 10:47 -0800, Dan Williams wrote:
> Commit cfe30b872058 "libnvdimm, pmem: adjust for section collisions with
> 'System RAM'" enabled Linux to workaround occasions where platform
> firmware arranges for "System RAM" and "Persistent Memory" to collide
> within a single section boundary. Unfortunately, as reported in this
> issue [1], platform firmware can inflict the same collision between
> persistent memory regions.
>
> The approach of interrogating iomem_resource does not work in this
> case because platform firmware may merge multiple regions into a single
> iomem_resource range. Instead provide a method to interrogate regions
> that share the same parent bus.
>
> This is a stop-gap until the core-MM can grow support for hotplug on
> sub-section boundaries.
>
> [1]: https://github.com/pmem/ndctl/issues/76
>
> Fixes: cfe30b872058 ("libnvdimm, pmem: adjust for section collisions with...")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> drivers/nvdimm/nd-core.h | 2 +
> drivers/nvdimm/pfn_devs.c | 64 ++++++++++++++++++++++++------------------
> drivers/nvdimm/region_devs.c | 41 +++++++++++++++++++++++++++
> 3 files changed, 80 insertions(+), 27 deletions(-)

Looks good to me,
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>

>
> diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h
> index 182258f64417..d0c621b32f72 100644
> --- a/drivers/nvdimm/nd-core.h
> +++ b/drivers/nvdimm/nd-core.h
> @@ -111,6 +111,8 @@ resource_size_t nd_pmem_available_dpa(struct nd_region *nd_region,
> struct nd_mapping *nd_mapping, resource_size_t *overlap);
> resource_size_t nd_blk_available_dpa(struct nd_region *nd_region);
> resource_size_t nd_region_available_dpa(struct nd_region *nd_region);
> +int nd_region_conflict(struct nd_region *nd_region, resource_size_t start,
> + resource_size_t size);
> resource_size_t nvdimm_allocated_dpa(struct nvdimm_drvdata *ndd,
> struct nd_label_id *label_id);
> int alias_dpa_busy(struct device *dev, void *data);
> diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
> index 24c64090169e..6f22272e8d80 100644
> --- a/drivers/nvdimm/pfn_devs.c
> +++ b/drivers/nvdimm/pfn_devs.c
> @@ -649,14 +649,47 @@ static u64 phys_pmem_align_down(struct nd_pfn *nd_pfn, u64 phys)
> ALIGN_DOWN(phys, nd_pfn->align));
> }
>
> +/*
> + * Check if pmem collides with 'System RAM', or other regions when
> + * section aligned. Trim it accordingly.
> + */
> +static void trim_pfn_device(struct nd_pfn *nd_pfn, u32 *start_pad, u32 *end_trunc)
> +{
> + struct nd_namespace_common *ndns = nd_pfn->ndns;
> + struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
> + struct nd_region *nd_region = to_nd_region(nd_pfn->dev.parent);
> + const resource_size_t start = nsio->res.start;
> + const resource_size_t end = start + resource_size(&nsio->res);
> + resource_size_t adjust, size;
> +
> + *start_pad = 0;
> + *end_trunc = 0;
> +
> + adjust = start - PHYS_SECTION_ALIGN_DOWN(start);
> + size = resource_size(&nsio->res) + adjust;
> + if (region_intersects(start - adjust, size, IORESOURCE_SYSTEM_RAM,
> + IORES_DESC_NONE) == REGION_MIXED
> + || nd_region_conflict(nd_region, start - adjust, size))
> + *start_pad = PHYS_SECTION_ALIGN_UP(start) - start;
> +
> + /* Now check that end of the range does not collide. */
> + adjust = PHYS_SECTION_ALIGN_UP(end) - end;
> + size = resource_size(&nsio->res) + adjust;
> + if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM,
> + IORES_DESC_NONE) == REGION_MIXED
> + || !IS_ALIGNED(end, nd_pfn->align)
> + || nd_region_conflict(nd_region, start, size + adjust))
> + *end_trunc = end - phys_pmem_align_down(nd_pfn, end);
> +}
> +
> static int nd_pfn_init(struct nd_pfn *nd_pfn)
> {
> u32 dax_label_reserve = is_nd_dax(&nd_pfn->dev) ? SZ_128K : 0;
> struct nd_namespace_common *ndns = nd_pfn->ndns;
> - u32 start_pad = 0, end_trunc = 0;
> + struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
> resource_size_t start, size;
> - struct nd_namespace_io *nsio;
> struct nd_region *nd_region;
> + u32 start_pad, end_trunc;
> struct nd_pfn_sb *pfn_sb;
> unsigned long npfns;
> phys_addr_t offset;
> @@ -688,30 +721,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
>
> memset(pfn_sb, 0, sizeof(*pfn_sb));
>
> - /*
> - * Check if pmem collides with 'System RAM' when section aligned and
> - * trim it accordingly
> - */
> - nsio = to_nd_namespace_io(&ndns->dev);
> - start = PHYS_SECTION_ALIGN_DOWN(nsio->res.start);
> - size = resource_size(&nsio->res);
> - if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM,
> - IORES_DESC_NONE) == REGION_MIXED) {
> - start = nsio->res.start;
> - start_pad = PHYS_SECTION_ALIGN_UP(start) - start;
> - }
> -
> - start = nsio->res.start;
> - size = PHYS_SECTION_ALIGN_UP(start + size) - start;
> - if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM,
> - IORES_DESC_NONE) == REGION_MIXED
> - || !IS_ALIGNED(start + resource_size(&nsio->res),
> - nd_pfn->align)) {
> - size = resource_size(&nsio->res);
> - end_trunc = start + size - phys_pmem_align_down(nd_pfn,
> - start + size);
> - }
> -
> + trim_pfn_device(nd_pfn, &start_pad, &end_trunc);
> if (start_pad + end_trunc)
> dev_info(&nd_pfn->dev, "%s alignment collision, truncate %d bytes\n",
> dev_name(&ndns->dev), start_pad + end_trunc);
> @@ -722,7 +732,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
> * implementation will limit the pfns advertised through
> * ->direct_access() to those that are included in the memmap.
> */
> - start += start_pad;
> + start = nsio->res.start + start_pad;
> size = resource_size(&nsio->res);
> npfns = PFN_SECTION_ALIGN_UP((size - start_pad - end_trunc - SZ_8K)
> / PAGE_SIZE);
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index 174a418cb171..e7377f1028ef 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -1184,6 +1184,47 @@ int nvdimm_has_cache(struct nd_region *nd_region)
> }
> EXPORT_SYMBOL_GPL(nvdimm_has_cache);
>
> +struct conflict_context {
> + struct nd_region *nd_region;
> + resource_size_t start, size;
> +};
> +
> +static int region_conflict(struct device *dev, void *data)
> +{
> + struct nd_region *nd_region;
> + struct conflict_context *ctx = data;
> + resource_size_t res_end, region_end, region_start;
> +
> + if (!is_memory(dev))
> + return 0;
> +
> + nd_region = to_nd_region(dev);
> + if (nd_region == ctx->nd_region)
> + return 0;
> +
> + res_end = ctx->start + ctx->size;
> + region_start = nd_region->ndr_start;
> + region_end = region_start + nd_region->ndr_size;
> + if (ctx->start >= region_start && ctx->start < region_end)
> + return -EBUSY;
> + if (res_end > region_start && res_end <= region_end)
> + return -EBUSY;
> + return 0;
> +}
> +
> +int nd_region_conflict(struct nd_region *nd_region, resource_size_t start,
> + resource_size_t size)
> +{
> + struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(&nd_region->dev);
> + struct conflict_context ctx = {
> + .nd_region = nd_region,
> + .start = start,
> + .size = size,
> + };
> +
> + return device_for_each_child(&nvdimm_bus->dev, &ctx, region_conflict);
> +}
> +
> void __exit nd_region_devs_exit(void)
> {
> ida_destroy(&region_ida);
>

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