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Message-ID: <62acc746d01d3_81c5e29441@dwillia2-xfh.notmuch>
Date: Fri, 17 Jun 2022 11:26:14 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: <alison.schofield@...el.com>,
Dan Williams <dan.j.williams@...el.com>,
"Ira Weiny" <ira.weiny@...el.com>,
Vishal Verma <vishal.l.verma@...el.com>,
"Ben Widawsky" <bwidawsk@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
"Ingo Molnar" <mingo@...hat.com>
CC: Alison Schofield <alison.schofield@...el.com>,
<linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/3] cxl/mbox: Add GET_POISON_LIST mailbox command support
alison.schofield@ wrote:
> From: Alison Schofield <alison.schofield@...el.com>
>
> CXL devices that support persistent memory maintain a list of locations
> that are poisoned or result in poison if the addresses are accessed by
> the host.
>
> Per the spec (CXL 2.0 8.2.8.5.4.1), the device returns this Poison
> list as a set of Media Error Records that include the source of the
> error, the starting device physical address and length. The length is
> the number of adjacent DPAs in the record and is in units of 64 bytes.
>
> Retrieve the list and log each Media Error Record as a trace event of
> type cxl_poison_list.
>
> Signed-off-by: Alison Schofield <alison.schofield@...el.com>
> ---
> drivers/cxl/cxlmem.h | 43 +++++++++++++++++++++++
> drivers/cxl/core/mbox.c | 75 +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 118 insertions(+)
>
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index 60d10ee1e7fc..29cf0459b44a 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -174,6 +174,7 @@ struct cxl_endpoint_dvsec_info {
> * (CXL 2.0 8.2.8.4.3 Mailbox Capabilities Register)
> * @lsa_size: Size of Label Storage Area
> * (CXL 2.0 8.2.9.5.1.1 Identify Memory Device)
> + * @poison_max_mer: maximum Media Error Records tracked in Poison List
> * @mbox_mutex: Mutex to synchronize mailbox access.
> * @firmware_version: Firmware version for the memory device.
> * @enabled_cmds: Hardware commands found enabled in CEL.
> @@ -204,6 +205,7 @@ struct cxl_dev_state {
>
> size_t payload_size;
> size_t lsa_size;
> + u32 poison_max;
> struct mutex mbox_mutex; /* Protects device mailbox and firmware */
> char firmware_version[0x10];
> DECLARE_BITMAP(enabled_cmds, CXL_MEM_COMMAND_ID_MAX);
> @@ -317,6 +319,46 @@ struct cxl_mbox_set_partition_info {
>
> #define CXL_SET_PARTITION_IMMEDIATE_FLAG BIT(0)
>
> +struct cxl_mbox_poison_payload_in {
> + __le64 offset;
> + __le64 length;
> +} __packed;
> +
> +struct cxl_mbox_poison_payload_out {
> + u8 flags;
> + u8 rsvd1;
> + __le64 overflow_timestamp;
> + __le16 count;
> + u8 rsvd2[0x14];
> + struct cxl_poison_record {
> + __le64 address;
> + __le32 length;
> + __le32 rsvd;
> + } __packed record[];
> +} __packed;
> +
> +/* CXL 8.2.9.5.4.1 Get Poison List: payload out flags: */
> +#define CXL_POISON_FLAG_MORE BIT(0)
> +#define CXL_POISON_FLAG_OVERFLOW BIT(1)
> +#define CXL_POISON_FLAG_SCANNING BIT(2)
> +
> +/* CXL 8.2.9.5.4.1 Get Poison List: Error is encoded in record.address[2:0] */
> +#define CXL_POISON_SOURCE_MASK GENMASK(2, 0)
> +#define CXL_POISON_SOURCE_UNKNOWN 0
> +#define CXL_POISON_SOURCE_EXTERNAL 1
> +#define CXL_POISON_SOURCE_INTERNAL 2
> +#define CXL_POISON_SOURCE_INJECTED 3
> +#define CXL_POISON_SOURCE_VENDOR 7
> +
> +/* Software define */
> +#define CXL_POISON_SOURCE_INVALID 99
> +#define CXL_POISON_SOURCE_VALID(x) \
> + (((x) == CXL_POISON_SOURCE_UNKNOWN) || \
> + ((x) == CXL_POISON_SOURCE_EXTERNAL) || \
> + ((x) == CXL_POISON_SOURCE_INTERNAL) || \
> + ((x) == CXL_POISON_SOURCE_INJECTED) || \
> + ((x) == CXL_POISON_SOURCE_VENDOR))
> +
> /**
> * struct cxl_mem_command - Driver representation of a memory device command
> * @info: Command information as it exists for the UAPI
> @@ -351,6 +393,7 @@ int cxl_mem_create_range_info(struct cxl_dev_state *cxlds);
> struct cxl_dev_state *cxl_dev_state_create(struct device *dev);
> void set_exclusive_cxl_commands(struct cxl_dev_state *cxlds, unsigned long *cmds);
> void clear_exclusive_cxl_commands(struct cxl_dev_state *cxlds, unsigned long *cmds);
> +int cxl_mem_get_poison_list(struct device *dev);
> #ifdef CONFIG_CXL_SUSPEND
> void cxl_mem_active_inc(void);
> void cxl_mem_active_dec(void);
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 54f434733b56..c10c7020ebc2 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -9,6 +9,9 @@
>
> #include "core.h"
>
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/cxl.h>
> +
> static bool cxl_raw_allow_all;
>
> /**
> @@ -755,6 +758,7 @@ int cxl_dev_state_identify(struct cxl_dev_state *cxlds)
> {
> /* See CXL 2.0 Table 175 Identify Memory Device Output Payload */
> struct cxl_mbox_identify id;
> + __le32 val = 0;
> int rc;
>
> rc = cxl_mbox_send_cmd(cxlds, CXL_MBOX_OP_IDENTIFY, NULL, 0, &id,
> @@ -783,6 +787,9 @@ int cxl_dev_state_identify(struct cxl_dev_state *cxlds)
> cxlds->lsa_size = le32_to_cpu(id.lsa_size);
> memcpy(cxlds->firmware_version, id.fw_revision, sizeof(id.fw_revision));
>
> + memcpy(&val, id.poison_list_max_mer, 3);
> + cxlds->poison_max = le32_to_cpu(val);
> +
> return 0;
> }
> EXPORT_SYMBOL_NS_GPL(cxl_dev_state_identify, CXL);
> @@ -826,6 +833,74 @@ int cxl_mem_create_range_info(struct cxl_dev_state *cxlds)
> }
> EXPORT_SYMBOL_NS_GPL(cxl_mem_create_range_info, CXL);
>
> +int cxl_mem_get_poison_list(struct device *dev)
> +{
> + struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
> + struct cxl_dev_state *cxlds = cxlmd->cxlds;
> + struct cxl_mbox_poison_payload_out *po;
> + struct cxl_mbox_poison_payload_in pi;
> + int nr_records = 0;
> + int rc, i;
> +
> + if (range_len(&cxlds->pmem_range)) {
> + pi.offset = cpu_to_le64(cxlds->pmem_range.start);
> + pi.length = cpu_to_le64(range_len(&cxlds->pmem_range));
> + } else {
> + return -ENXIO;
> + }
> +
> + po = kvmalloc(cxlds->payload_size, GFP_KERNEL);
> + if (!po)
> + return -ENOMEM;
> +
> + do {
> + rc = cxl_mbox_send_cmd(cxlds, CXL_MBOX_OP_GET_POISON, &pi,
> + sizeof(pi), po, cxlds->payload_size);
> + if (rc)
> + goto out;
In this case, no need for a 'goto' when 'break' will do.
> +
> + if (po->flags & CXL_POISON_FLAG_OVERFLOW) {
> + time64_t o_time = le64_to_cpu(po->overflow_timestamp);
> +
> + dev_err(dev, "Poison list overflow at %ptTs UTC\n",
> + &o_time);
This should be just another event type, not an error message.
> + rc = -ENXIO;
No need to error out, the media error records are still valid.
> + goto out;
> + }
> +
> + if (po->flags & CXL_POISON_FLAG_SCANNING) {
> + dev_err(dev, "Scan Media in Progress\n");
This isn't an error condition and it should be something the kernel is
mediating in the first instance. For example if userspace did:
echo 1 > trace_poison &
echo 1 > trace_poison_cached
I would expect the second echo to just block awaiting the completion of
the scan media request. I.e. just prevent the possibility of these
commands colliding outside of CONFIG_CXL_MEM_RAW_COMMANDS=y shenanigans,
in which case userspace gets to keep the pieces.
> + rc = -EBUSY;
> + goto out;
> + }
> +
> + for (i = 0; i < le16_to_cpu(po->count); i++) {
> + u64 addr = le64_to_cpu(po->record[i].address);
> + u32 len = le32_to_cpu(po->record[i].length);
> + int source = FIELD_GET(CXL_POISON_SOURCE_MASK, addr);
> +
> + if (!CXL_POISON_SOURCE_VALID(source)) {
> + dev_dbg(dev, "Invalid poison source %d",
> + source);
Per above, just emit the raw field value and leave parsing values to
userspace.
> + source = CXL_POISON_SOURCE_INVALID;
> + }
> +
> + trace_cxl_poison_list(dev, source, addr, len);
> + }
> +
> + /* Protect against an uncleared _FLAG_MORE */
> + nr_records = nr_records + le16_to_cpu(po->count);
> + if (nr_records >= cxlds->poison_max)
> + goto out;
This also feels like something that should have a Linux max as well,
something like:
"cxlds->poison_max = min(identify->poison_max, CXL_LIST_POISON_MAX)"
...where CXL_LIST_POISON_MAX is a "reasonable" maximum for a cache of
hardware media poison errors like 1024.
> +
> + } while (po->flags & CXL_POISON_FLAG_MORE);
> +
> +out:
> + kvfree(po);
> + return rc;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_mem_get_poison_list, CXL);
> +
> struct cxl_dev_state *cxl_dev_state_create(struct device *dev)
> {
> struct cxl_dev_state *cxlds;
> --
> 2.31.1
>
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