Date:   Mon, 3 Dec 2018 18:37:48 +0000
From:   "Verma, Vishal L" <vishal.l.verma@...el.com>
To:     "Williams, Dan J" <dan.j.williams@...el.com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH 2/2] libnvdimm, pfn: Pad pfn namespaces relative to
 other regions


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@...r.kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@...el.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@...el.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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