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Date: Mon, 6 Jun 2022 12:32:20 -0700
From: Ben Widawsky <bwidawsk@...nel.org>
To: ira.weiny@...el.com
Cc: Dan Williams <dan.j.williams@...el.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Alison Schofield <alison.schofield@...el.com>,
Vishal Verma <vishal.l.verma@...el.com>,
Dave Jiang <dave.jiang@...el.com>,
linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org,
linux-pci@...r.kernel.org
Subject: Re: [PATCH V10 9/9] cxl/port: Parse out DSMAS data from CDAT table
On 22-06-04 17:50:49, ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.com>
>
> CXL Ports with memory devices attached need the information from the
> Device Scoped Memory Affinity Structure (DSMAS). This information is
> contained within the CDAT table buffer which is previously read and
> cached in the port device.
>
> If CDAT data is available, parse and cache DSMAS data from the table.
> Store this data in unmarshaled struct dsmas data structures for ease of
> use later.
>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
>
> ---
> Changes from V8
> Adjust to the cdat data being in cxl_port
>
> Changes from V7
> Rebased on cxl-pending
>
> Changes from V6
> Move to port.c
> It is not an error if no DSMAS data is found
>
> Changes from V5
> Fix up sparse warnings
> Split out cdat_hdr_valid()
> Update cdat_hdr_valid()
> Remove revision and cs field parsing
> There is no point in these
> Add seq check and debug print.
> From Jonathan
> Add spaces around '+' and '/'
> use devm_krealloc() for dmas_ary
> ---
> drivers/cxl/cdat.h | 17 +++++++++++
> drivers/cxl/core/pci.c | 65 ++++++++++++++++++++++++++++++++++++++++++
> drivers/cxl/cxl.h | 2 ++
> drivers/cxl/cxlmem.h | 4 +++
> drivers/cxl/cxlpci.h | 1 +
> drivers/cxl/mem.c | 1 +
> 6 files changed, 90 insertions(+)
>
> diff --git a/drivers/cxl/cdat.h b/drivers/cxl/cdat.h
> index 3d8945612511..0a510f73fe6d 100644
> --- a/drivers/cxl/cdat.h
> +++ b/drivers/cxl/cdat.h
> @@ -85,6 +85,23 @@
>
> #define CXL_DOE_PROTOCOL_TABLE_ACCESS 2
>
> +/**
> + * struct cxl_dsmas - host unmarshaled version of DSMAS data
> + *
> + * As defined in the Coherent Device Attribute Table (CDAT) specification this
> + * represents a single DSMAS entry in that table.
> + *
> + * @dpa_base: The lowest Device Physical Address associated with this DSMAD
> + * @length: Length in bytes of this DSMAD
> + * @non_volatile: If set, the memory region represents Non-Volatile memory
> + */
> +struct cxl_dsmas {
> + u64 dpa_base;
> + u64 length;
> + /* Flags */
> + u8 non_volatile:1;
> +};
> +
> /**
> * struct cxl_cdat - CXL CDAT data
> *
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index e68f13e66fcf..9666cc4a67aa 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -673,3 +673,68 @@ void read_cdat_data(struct cxl_port *port)
> retries);
> }
> EXPORT_SYMBOL_NS_GPL(read_cdat_data, CXL);
> +
> +void parse_dsmas(struct cxl_memdev *cxlmd, struct cxl_port *port)
> +{
> + struct device *dev = &port->dev;
> + struct cxl_dsmas *dsmas_ary = NULL;
> + u32 *data = port->cdat.table;
> + int bytes_left = port->cdat.length;
> + int nr_dsmas = 0;
> +
> + if (!data) {
> + dev_info(dev, "No CDAT data available for DSMAS\n");
> + return;
> + }
> +
> + /* Skip header */
> + data += CDAT_HEADER_LENGTH_DW;
> + bytes_left -= CDAT_HEADER_LENGTH_BYTES;
> +
> + while (bytes_left > 0) {
> + u32 *cur_rec = data;
> + u8 type = FIELD_GET(CDAT_STRUCTURE_DW0_TYPE, cur_rec[0]);
> + u16 length = FIELD_GET(CDAT_STRUCTURE_DW0_LENGTH, cur_rec[0]);
> +
> + if (type == CDAT_STRUCTURE_DW0_TYPE_DSMAS) {
> + struct cxl_dsmas *new_ary;
> + u8 flags;
> +
> + new_ary = devm_krealloc(dev, dsmas_ary,
> + sizeof(*dsmas_ary) * (nr_dsmas + 1),
> + GFP_KERNEL);
> + if (!new_ary) {
> + dev_err(dev,
> + "Failed to allocate memory for DSMAS data (nr_dsmas %d)\n",
> + nr_dsmas);
> + return;
> + }
> + dsmas_ary = new_ary;
I don't love the realloc on every loop (though I've done something similar
before). What about allocating enough entries port->cdat.length, and then a
single krealloc to shorten the array upon success? I think krealloc pretty much
always succeeds when you shrink FWIW.
> +
> + flags = FIELD_GET(CDAT_DSMAS_DW1_FLAGS, cur_rec[1]);
Does it make sense to test length/bytes_left before reading cur_rec[1]?
> +
> + dsmas_ary[nr_dsmas].dpa_base = CDAT_DSMAS_DPA_OFFSET(cur_rec);
> + dsmas_ary[nr_dsmas].length = CDAT_DSMAS_DPA_LEN(cur_rec);
> + dsmas_ary[nr_dsmas].non_volatile = CDAT_DSMAS_NON_VOLATILE(flags);
> +
> + dev_dbg(dev, "DSMAS %d: %llx:%llx %s\n",
> + nr_dsmas,
> + dsmas_ary[nr_dsmas].dpa_base,
> + dsmas_ary[nr_dsmas].dpa_base +
> + dsmas_ary[nr_dsmas].length,
> + (dsmas_ary[nr_dsmas].non_volatile ?
> + "Persistent" : "Volatile")
> + );
> +
> + nr_dsmas++;
> + }
> +
> + data += (length / sizeof(u32));
> + bytes_left -= length;
> + }
> +
> + dev_dbg(dev, "Found %d DSMAS entries\n", nr_dsmas);
> + cxlmd->dsmas_ary = dsmas_ary;
> + cxlmd->nr_dsmas = nr_dsmas;
> +}
> +EXPORT_SYMBOL_NS_GPL(parse_dsmas, CXL);
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 531b77d296c7..4d779a8fb807 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -10,6 +10,8 @@
> #include <linux/io.h>
> #include "cdat.h"
>
> +#include "cdat.h"
> +
> /**
> * DOC: cxl objects
> *
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index 4d2764b865ab..ce5b00f3ebcb 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -36,6 +36,8 @@
> * @cxlds: The device state backing this device
> * @detach_work: active memdev lost a port in its ancestry
> * @id: id number of this memdev instance.
> + * @dsmas_ary: Array of DSMAS entries as parsed from the CDAT table
> + * @nr_dsmas: Number of entries in dsmas_ary
Personally don't think it's necessary to append "_ary". Up to you.
> */
> struct cxl_memdev {
> struct device dev;
> @@ -43,6 +45,8 @@ struct cxl_memdev {
> struct cxl_dev_state *cxlds;
> struct work_struct detach_work;
> int id;
> + struct cxl_dsmas *dsmas_ary;
> + int nr_dsmas;
> };
>
> static inline struct cxl_memdev *to_cxl_memdev(struct device *dev)
> diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
> index 71009a167a92..44d1c2b83aab 100644
> --- a/drivers/cxl/cxlpci.h
> +++ b/drivers/cxl/cxlpci.h
> @@ -76,4 +76,5 @@ struct cxl_dev_state;
> int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm);
> void cxl_cache_cdat_mb(struct cxl_port *port);
> void read_cdat_data(struct cxl_port *port);
> +void parse_dsmas(struct cxl_memdev *cxlmd, struct cxl_port *port);
> #endif /* __CXL_PCI_H__ */
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index c310f1fd3db0..a8768df4ae38 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -35,6 +35,7 @@ static int create_endpoint(struct cxl_memdev *cxlmd,
> if (IS_ERR(endpoint))
> return PTR_ERR(endpoint);
>
> + parse_dsmas(cxlmd, endpoint);
> dev_dbg(&cxlmd->dev, "add: %s\n", dev_name(&endpoint->dev));
>
> if (!endpoint->dev.driver) {
> --
> 2.35.1
>
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