[PATCH v2 0/2] scsi: scsi_debug: Support hostwide tags and a fix

[PATCH v2 0/2] scsi: scsi_debug: Support hostwide tags and a fix

[John Garry]

This series includes hostwide tags support, so we can mimic some SCSI HBAs,
like megaraid sas or hisi_sas.

There is also a fix for an out-of-range module param.

Differences to v1:
- add Doug's Ack for patch 1/2
- sort params alphabetically
- fix max queue at host max queue (when non-zero)
- drop host max queue file write permission

John Garry (2):
  scsi: scsi_debug: Add check for sdebug_max_queue during module init
  scsi: scsi_debug: Support hostwide tags

 drivers/scsi/scsi_debug.c | 86 +++++++++++++++++++++++++++++++++------
 1 file changed, 74 insertions(+), 12 deletions(-)

-- 
2.26.2

[PATCH v2 1/2] scsi: scsi_debug: Add check for sdebug_max_queue during module init

[John Garry]

sdebug_max_queue should not exceed SDEBUG_CANQUEUE, otherwise crashes like
this can be triggered by passing an out-of-range value:

Hardware name: Huawei D06 /D06, BIOS Hisilicon D06 UEFI RC0 - V1.16.01 03/15/2019 
 pstate: 20400009 (nzCv daif +PAN -UAO BTYPE=--) 
 pc : schedule_resp+0x2a4/0xa70 [scsi_debug] 
 lr : schedule_resp+0x52c/0xa70 [scsi_debug] 
 sp : ffff800022ab36f0 
 x29: ffff800022ab36f0 x28: ffff0023a935a610 
 x27: ffff800008e0a648 x26: 0000000000000003 
 x25: ffff0023e84f3200 x24: 00000000003d0900 
 x23: 0000000000000000 x22: 0000000000000000 
 x21: ffff0023be60a320 x20: ffff0023be60b538 
 x19: ffff800008e13000 x18: 0000000000000000 
 x17: 0000000000000000 x16: 0000000000000000 
 x15: 0000000000000000 x14: 0000000000000000 
 x13: 0000000000000000 x12: 0000000000000000 
 x11: 0000000000000000 x10: 0000000000000000 
 x9 : 0000000000000001 x8 : 0000000000000000 
 x7 : 0000000000000000 x6 : 00000000000000c1 
 x5 : 0000020000200000 x4 : dead0000000000ff 
 x3 : 0000000000000200 x2 : 0000000000000200 
 x1 : ffff800008e13d88 x0 : 0000000000000000 
 Call trace: 
schedule_resp+0x2a4/0xa70 [scsi_debug] 
scsi_debug_queuecommand+0x2c4/0x9e0 [scsi_debug] 
scsi_queue_rq+0x698/0x840
__blk_mq_try_issue_directly+0x108/0x228
blk_mq_request_issue_directly+0x58/0x98
blk_mq_try_issue_list_directly+0x5c/0xf0 
blk_mq_sched_insert_requests+0x18c/0x200 
blk_mq_flush_plug_list+0x11c/0x190 
blk_flush_plug_list+0xdc/0x110 
blk_finish_plug+0x38/0x210 
blkdev_direct_IO+0x450/0x4d8 
generic_file_read_iter+0x84/0x180
blkdev_read_iter+0x3c/0x50 
aio_read+0xc0/0x170
io_submit_one+0x5c8/0xc98
__arm64_sys_io_submit+0x1b0/0x258
el0_svc_common.constprop.3+0x68/0x170
do_el0_svc+0x24/0x90 
el0_sync_handler+0x13c/0x1a8 
el0_sync+0x158/0x180 
 Code: 528847e0 72a001e0 6b00003f 540018cd (3941c340)

In addition, it should not be less than 1.

So add checks for these, and fail the module init for those cases.

Fixes: c483739430f10 ("scsi_debug: add multiple queue support")
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: John Garry <john.garry@huawei.com>
---
 drivers/scsi/scsi_debug.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 4692f5b6ad13..68534a23866e 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -6613,6 +6613,12 @@ static int __init scsi_debug_init(void)
 		pr_err("submit_queues must be 1 or more\n");
 		return -EINVAL;
 	}
+
+	if ((sdebug_max_queue > SDEBUG_CANQUEUE) || (sdebug_max_queue <= 0)) {
+		pr_err("max_queue must be in range [1, %d]\n", SDEBUG_CANQUEUE);
+		return -EINVAL;
+	}
+
 	sdebug_q_arr = kcalloc(submit_queues, sizeof(struct sdebug_queue),
 			       GFP_KERNEL);
 	if (sdebug_q_arr == NULL)
-- 
2.26.2

Re: [PATCH v2 1/2] scsi: scsi_debug: Add check for sdebug_max_queue during module init

[Ming Lei]

On Thu, Jul 09, 2020 at 08:23:19PM +0800, John Garry wrote:
> sdebug_max_queue should not exceed SDEBUG_CANQUEUE, otherwise crashes like
> this can be triggered by passing an out-of-range value:
> 
> Hardware name: Huawei D06 /D06, BIOS Hisilicon D06 UEFI RC0 - V1.16.01 03/15/2019 
>  pstate: 20400009 (nzCv daif +PAN -UAO BTYPE=--) 
>  pc : schedule_resp+0x2a4/0xa70 [scsi_debug] 
>  lr : schedule_resp+0x52c/0xa70 [scsi_debug] 
>  sp : ffff800022ab36f0 
>  x29: ffff800022ab36f0 x28: ffff0023a935a610 
>  x27: ffff800008e0a648 x26: 0000000000000003 
>  x25: ffff0023e84f3200 x24: 00000000003d0900 
>  x23: 0000000000000000 x22: 0000000000000000 
>  x21: ffff0023be60a320 x20: ffff0023be60b538 
>  x19: ffff800008e13000 x18: 0000000000000000 
>  x17: 0000000000000000 x16: 0000000000000000 
>  x15: 0000000000000000 x14: 0000000000000000 
>  x13: 0000000000000000 x12: 0000000000000000 
>  x11: 0000000000000000 x10: 0000000000000000 
>  x9 : 0000000000000001 x8 : 0000000000000000 
>  x7 : 0000000000000000 x6 : 00000000000000c1 
>  x5 : 0000020000200000 x4 : dead0000000000ff 
>  x3 : 0000000000000200 x2 : 0000000000000200 
>  x1 : ffff800008e13d88 x0 : 0000000000000000 
>  Call trace: 
> schedule_resp+0x2a4/0xa70 [scsi_debug] 
> scsi_debug_queuecommand+0x2c4/0x9e0 [scsi_debug] 
> scsi_queue_rq+0x698/0x840
> __blk_mq_try_issue_directly+0x108/0x228
> blk_mq_request_issue_directly+0x58/0x98
> blk_mq_try_issue_list_directly+0x5c/0xf0 
> blk_mq_sched_insert_requests+0x18c/0x200 
> blk_mq_flush_plug_list+0x11c/0x190 
> blk_flush_plug_list+0xdc/0x110 
> blk_finish_plug+0x38/0x210 
> blkdev_direct_IO+0x450/0x4d8 
> generic_file_read_iter+0x84/0x180
> blkdev_read_iter+0x3c/0x50 
> aio_read+0xc0/0x170
> io_submit_one+0x5c8/0xc98
> __arm64_sys_io_submit+0x1b0/0x258
> el0_svc_common.constprop.3+0x68/0x170
> do_el0_svc+0x24/0x90 
> el0_sync_handler+0x13c/0x1a8 
> el0_sync+0x158/0x180 
>  Code: 528847e0 72a001e0 6b00003f 540018cd (3941c340)
> 
> In addition, it should not be less than 1.
> 
> So add checks for these, and fail the module init for those cases.
> 
> Fixes: c483739430f10 ("scsi_debug: add multiple queue support")
> Acked-by: Douglas Gilbert <dgilbert@interlog.com>
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>  drivers/scsi/scsi_debug.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index 4692f5b6ad13..68534a23866e 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -6613,6 +6613,12 @@ static int __init scsi_debug_init(void)
>  		pr_err("submit_queues must be 1 or more\n");
>  		return -EINVAL;
>  	}
> +
> +	if ((sdebug_max_queue > SDEBUG_CANQUEUE) || (sdebug_max_queue <= 0)) {
> +		pr_err("max_queue must be in range [1, %d]\n", SDEBUG_CANQUEUE);
> +		return -EINVAL;
> +	}
> +
>  	sdebug_q_arr = kcalloc(submit_queues, sizeof(struct sdebug_queue),
>  			       GFP_KERNEL);
>  	if (sdebug_q_arr == NULL)
> -- 
> 2.26.2
> 

Reviewed-by: Ming Lei <ming.lei@redhat.com>

-- 
Ming

[PATCH v2 2/2] scsi: scsi_debug: Support hostwide tags

[John Garry]

Many SCSI HBAs support a hostwide tagset, whereby each command submitted
to the HW from all submission queues must have a unique tag identifier.

Normally this unique tag will be in the range [0, max queue), where "max
queue" is the depth of each of the submission queues.

Add support for this hostwide tag feature, via module parameter
"host_max_queue". A non-zero value means that the feature is enabled. In
this case, the submission queues are not exposed to upper layer, i.e. from
blk-mq prespective, the device has a single hw queue. There are 2 reasons
for this:
a. it is assumed that the host can support nr_hw_queues * can_queue
   commands, but this is not true for hostwide tags
b. for nr_hw_queues != 0, the request tag is not unique over all HW queues,
   and some HBA drivers want to use this tag for the hostwide tag

However, like many SCSI HBA drivers today - megaraid sas being an example -
the full set of HW submission queues are still used in the LLDD driver. So
instead of using a complicated "reply_map" to create a per-CPU submission
queue mapping like megaraid sas (as it depends on a PCI device + MSIs) -
use a simple algorithm:

hwq = cpu % queue count

If the host max queue param is set non-zero, then the max queue depth is
fixed at this value also.

If and when hostwide shared tags are supported in blk-mq/scsi mid-layer,
then the policy to set nr_hw_queues = 0 for hostwide tags can be revised.

Signed-off-by: John Garry <john.garry@huawei.com>
---
 drivers/scsi/scsi_debug.c | 80 +++++++++++++++++++++++++++++++++------
 1 file changed, 68 insertions(+), 12 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 68534a23866e..2246d721ec88 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -344,6 +344,7 @@ struct sdebug_defer {
 	struct execute_work ew;
 	int sqa_idx;	/* index of sdebug_queue array */
 	int qc_idx;	/* index of sdebug_queued_cmd array within sqa_idx */
+	int hc_idx;	/* hostwide tag index */
 	int issuing_cpu;
 	bool init_hrt;
 	bool init_wq;
@@ -759,6 +760,7 @@ static int sdebug_dsense = DEF_D_SENSE;
 static int sdebug_every_nth = DEF_EVERY_NTH;
 static int sdebug_fake_rw = DEF_FAKE_RW;
 static unsigned int sdebug_guard = DEF_GUARD;
+static int sdebug_host_max_queue;	/* per host */
 static int sdebug_lowest_aligned = DEF_LOWEST_ALIGNED;
 static int sdebug_max_luns = DEF_MAX_LUNS;
 static int sdebug_max_queue = SDEBUG_CANQUEUE;	/* per submit queue */
@@ -4707,15 +4709,28 @@ static int resp_rwp_zone(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
 
 static struct sdebug_queue *get_queue(struct scsi_cmnd *cmnd)
 {
-	u32 tag = blk_mq_unique_tag(cmnd->request);
-	u16 hwq = blk_mq_unique_tag_to_hwq(tag);
+	u16 hwq;
 
-	pr_debug("tag=%#x, hwq=%d\n", tag, hwq);
-	if (WARN_ON_ONCE(hwq >= submit_queues))
-		hwq = 0;
+	if (sdebug_host_max_queue) {
+		/* Provide a simple method to choose the hwq */
+		hwq = smp_processor_id() % submit_queues;
+	} else {
+		u32 tag = blk_mq_unique_tag(cmnd->request);
+
+		hwq = blk_mq_unique_tag_to_hwq(tag);
+
+		pr_debug("tag=%#x, hwq=%d\n", tag, hwq);
+		if (WARN_ON_ONCE(hwq >= submit_queues))
+			hwq = 0;
+	}
 	return sdebug_q_arr + hwq;
 }
 
+static u32 get_tag(struct scsi_cmnd *cmnd)
+{
+	return blk_mq_unique_tag(cmnd->request);
+}
+
 /* Queued (deferred) command completions converge here. */
 static void sdebug_q_cmd_complete(struct sdebug_defer *sd_dp)
 {
@@ -4747,8 +4762,8 @@ static void sdebug_q_cmd_complete(struct sdebug_defer *sd_dp)
 	scp = sqcp->a_cmnd;
 	if (unlikely(scp == NULL)) {
 		spin_unlock_irqrestore(&sqp->qc_lock, iflags);
-		pr_err("scp is NULL, sqa_idx=%d, qc_idx=%d\n",
-		       sd_dp->sqa_idx, qc_idx);
+		pr_err("scp is NULL, sqa_idx=%d, qc_idx=%d, hc_idx=%d\n",
+		       sd_dp->sqa_idx, qc_idx, sd_dp->hc_idx);
 		return;
 	}
 	devip = (struct sdebug_dev_info *)scp->device->hostdata;
@@ -5451,6 +5466,10 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
 		new_sd_dp = false;
 	}
 
+	/* Set the hostwide tag */
+	if (sdebug_host_max_queue)
+		sd_dp->hc_idx = get_tag(cmnd);
+
 	if (ndelay > 0 && ndelay < INCLUSIVE_TIMING_MAX_NS)
 		ns_from_boot = ktime_get_boottime_ns();
 
@@ -5572,6 +5591,7 @@ module_param_named(every_nth, sdebug_every_nth, int, S_IRUGO | S_IWUSR);
 module_param_named(fake_rw, sdebug_fake_rw, int, S_IRUGO | S_IWUSR);
 module_param_named(guard, sdebug_guard, uint, S_IRUGO);
 module_param_named(host_lock, sdebug_host_lock, bool, S_IRUGO | S_IWUSR);
+module_param_named(host_max_queue, sdebug_host_max_queue, int, S_IRUGO);
 module_param_string(inq_product, sdebug_inq_product_id,
 		    sizeof(sdebug_inq_product_id), S_IRUGO | S_IWUSR);
 module_param_string(inq_rev, sdebug_inq_product_rev,
@@ -5642,6 +5662,8 @@ MODULE_PARM_DESC(every_nth, "timeout every nth command(def=0)");
 MODULE_PARM_DESC(fake_rw, "fake reads/writes instead of copying (def=0)");
 MODULE_PARM_DESC(guard, "protection checksum: 0=crc, 1=ip (def=0)");
 MODULE_PARM_DESC(host_lock, "host_lock is ignored (def=0)");
+MODULE_PARM_DESC(host_max_queue,
+		 "host max # of queued cmds (0 to max(def) [max_queue fixed equal for !0])");
 MODULE_PARM_DESC(inq_product, "SCSI INQUIRY product string (def=\"scsi_debug\")");
 MODULE_PARM_DESC(inq_rev, "SCSI INQUIRY revision string (def=\""
 		 SDEBUG_VERSION "\")");
@@ -6141,7 +6163,8 @@ static ssize_t max_queue_store(struct device_driver *ddp, const char *buf,
 	struct sdebug_queue *sqp;
 
 	if ((count > 0) && (1 == sscanf(buf, "%d", &n)) && (n > 0) &&
-	    (n <= SDEBUG_CANQUEUE)) {
+	    (n <= SDEBUG_CANQUEUE) &&
+	    (sdebug_host_max_queue == 0)) {
 		block_unblock_all_queues(true);
 		k = 0;
 		for (j = 0, sqp = sdebug_q_arr; j < submit_queues;
@@ -6164,6 +6187,17 @@ static ssize_t max_queue_store(struct device_driver *ddp, const char *buf,
 }
 static DRIVER_ATTR_RW(max_queue);
 
+static ssize_t host_max_queue_show(struct device_driver *ddp, char *buf)
+{
+	return scnprintf(buf, PAGE_SIZE, "%d\n", sdebug_host_max_queue);
+}
+
+/*
+ * Since this is used for .can_queue, and we get the hc_idx tag from the bitmap
+ * in range [0, sdebug_host_max_queue), we can't change it.
+ */
+static DRIVER_ATTR_RO(host_max_queue);
+
 static ssize_t no_uld_show(struct device_driver *ddp, char *buf)
 {
 	return scnprintf(buf, PAGE_SIZE, "%d\n", sdebug_no_uld);
@@ -6503,6 +6537,7 @@ static struct attribute *sdebug_drv_attrs[] = {
 	&driver_attr_ptype.attr,
 	&driver_attr_dsense.attr,
 	&driver_attr_fake_rw.attr,
+	&driver_attr_host_max_queue.attr,
 	&driver_attr_no_lun_0.attr,
 	&driver_attr_num_tgts.attr,
 	&driver_attr_dev_size_mb.attr,
@@ -6619,6 +6654,20 @@ static int __init scsi_debug_init(void)
 		return -EINVAL;
 	}
 
+	if ((sdebug_host_max_queue > SDEBUG_CANQUEUE) ||
+	    (sdebug_host_max_queue < 0)) {
+		pr_err("host_max_queue must be in range [0 %d]\n",
+		       SDEBUG_CANQUEUE);
+		return -EINVAL;
+	}
+
+	if (sdebug_host_max_queue &&
+	    (sdebug_max_queue != sdebug_host_max_queue)) {
+		sdebug_max_queue = sdebug_host_max_queue;
+		pr_warn("fixing max submit queue depth to host max queue depth, %d\n",
+			sdebug_max_queue);
+	}
+
 	sdebug_q_arr = kcalloc(submit_queues, sizeof(struct sdebug_queue),
 			       GFP_KERNEL);
 	if (sdebug_q_arr == NULL)
@@ -7257,7 +7306,10 @@ static int sdebug_driver_probe(struct device *dev)
 
 	sdbg_host = to_sdebug_host(dev);
 
-	sdebug_driver_template.can_queue = sdebug_max_queue;
+	if (sdebug_host_max_queue)
+		sdebug_driver_template.can_queue = sdebug_host_max_queue;
+	else
+		sdebug_driver_template.can_queue = sdebug_max_queue;
 	if (!sdebug_clustering)
 		sdebug_driver_template.dma_boundary = PAGE_SIZE - 1;
 
@@ -7272,9 +7324,13 @@ static int sdebug_driver_probe(struct device *dev)
 			my_name, submit_queues, nr_cpu_ids);
 		submit_queues = nr_cpu_ids;
 	}
-	/* Decide whether to tell scsi subsystem that we want mq */
-	/* Following should give the same answer for each host */
-	hpnt->nr_hw_queues = submit_queues;
+	/*
+	 * Decide whether to tell scsi subsystem that we want mq. The
+	 * following should give the same answer for each host. If the host
+	 * has a limit of hostwide max commands, then do not set.
+	 */
+	if (!sdebug_host_max_queue)
+		hpnt->nr_hw_queues = submit_queues;
 
 	sdbg_host->shost = hpnt;
 	*((struct sdebug_host_info **)hpnt->hostdata) = sdbg_host;
-- 
2.26.2

Re: [PATCH v2 2/2] scsi: scsi_debug: Support hostwide tags

[Douglas Gilbert]

On 2020-07-09 8:23 a.m., John Garry wrote:
> Many SCSI HBAs support a hostwide tagset, whereby each command submitted
> to the HW from all submission queues must have a unique tag identifier.
> 
> Normally this unique tag will be in the range [0, max queue), where "max
> queue" is the depth of each of the submission queues.
> 
> Add support for this hostwide tag feature, via module parameter
> "host_max_queue". A non-zero value means that the feature is enabled. In
> this case, the submission queues are not exposed to upper layer, i.e. from
> blk-mq prespective, the device has a single hw queue. There are 2 reasons
> for this:
> a. it is assumed that the host can support nr_hw_queues * can_queue
>     commands, but this is not true for hostwide tags
> b. for nr_hw_queues != 0, the request tag is not unique over all HW queues,
>     and some HBA drivers want to use this tag for the hostwide tag
> 
> However, like many SCSI HBA drivers today - megaraid sas being an example -
> the full set of HW submission queues are still used in the LLDD driver. So
> instead of using a complicated "reply_map" to create a per-CPU submission
> queue mapping like megaraid sas (as it depends on a PCI device + MSIs) -
> use a simple algorithm:
> 
> hwq = cpu % queue count
> 
> If the host max queue param is set non-zero, then the max queue depth is
> fixed at this value also.
> 
> If and when hostwide shared tags are supported in blk-mq/scsi mid-layer,
> then the policy to set nr_hw_queues = 0 for hostwide tags can be revised.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>

Acked-by: Douglas Gilbert <dgilbert@interlog.com>

I have updated this page to reflect this addition:
      http://sg.danny.cz/sg/scsi_debug.html

> ---
>   drivers/scsi/scsi_debug.c | 80 +++++++++++++++++++++++++++++++++------
>   1 file changed, 68 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index 68534a23866e..2246d721ec88 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -344,6 +344,7 @@ struct sdebug_defer {
>   	struct execute_work ew;
>   	int sqa_idx;	/* index of sdebug_queue array */
>   	int qc_idx;	/* index of sdebug_queued_cmd array within sqa_idx */
> +	int hc_idx;	/* hostwide tag index */
>   	int issuing_cpu;
>   	bool init_hrt;
>   	bool init_wq;
> @@ -759,6 +760,7 @@ static int sdebug_dsense = DEF_D_SENSE;
>   static int sdebug_every_nth = DEF_EVERY_NTH;
>   static int sdebug_fake_rw = DEF_FAKE_RW;
>   static unsigned int sdebug_guard = DEF_GUARD;
> +static int sdebug_host_max_queue;	/* per host */
>   static int sdebug_lowest_aligned = DEF_LOWEST_ALIGNED;
>   static int sdebug_max_luns = DEF_MAX_LUNS;
>   static int sdebug_max_queue = SDEBUG_CANQUEUE;	/* per submit queue */
> @@ -4707,15 +4709,28 @@ static int resp_rwp_zone(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
>   
>   static struct sdebug_queue *get_queue(struct scsi_cmnd *cmnd)
>   {
> -	u32 tag = blk_mq_unique_tag(cmnd->request);
> -	u16 hwq = blk_mq_unique_tag_to_hwq(tag);
> +	u16 hwq;
>   
> -	pr_debug("tag=%#x, hwq=%d\n", tag, hwq);
> -	if (WARN_ON_ONCE(hwq >= submit_queues))
> -		hwq = 0;
> +	if (sdebug_host_max_queue) {
> +		/* Provide a simple method to choose the hwq */
> +		hwq = smp_processor_id() % submit_queues;
> +	} else {
> +		u32 tag = blk_mq_unique_tag(cmnd->request);
> +
> +		hwq = blk_mq_unique_tag_to_hwq(tag);
> +
> +		pr_debug("tag=%#x, hwq=%d\n", tag, hwq);
> +		if (WARN_ON_ONCE(hwq >= submit_queues))
> +			hwq = 0;
> +	}
>   	return sdebug_q_arr + hwq;
>   }
>   
> +static u32 get_tag(struct scsi_cmnd *cmnd)
> +{
> +	return blk_mq_unique_tag(cmnd->request);
> +}
> +
>   /* Queued (deferred) command completions converge here. */
>   static void sdebug_q_cmd_complete(struct sdebug_defer *sd_dp)
>   {
> @@ -4747,8 +4762,8 @@ static void sdebug_q_cmd_complete(struct sdebug_defer *sd_dp)
>   	scp = sqcp->a_cmnd;
>   	if (unlikely(scp == NULL)) {
>   		spin_unlock_irqrestore(&sqp->qc_lock, iflags);
> -		pr_err("scp is NULL, sqa_idx=%d, qc_idx=%d\n",
> -		       sd_dp->sqa_idx, qc_idx);
> +		pr_err("scp is NULL, sqa_idx=%d, qc_idx=%d, hc_idx=%d\n",
> +		       sd_dp->sqa_idx, qc_idx, sd_dp->hc_idx);
>   		return;
>   	}
>   	devip = (struct sdebug_dev_info *)scp->device->hostdata;
> @@ -5451,6 +5466,10 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
>   		new_sd_dp = false;
>   	}
>   
> +	/* Set the hostwide tag */
> +	if (sdebug_host_max_queue)
> +		sd_dp->hc_idx = get_tag(cmnd);
> +
>   	if (ndelay > 0 && ndelay < INCLUSIVE_TIMING_MAX_NS)
>   		ns_from_boot = ktime_get_boottime_ns();
>   
> @@ -5572,6 +5591,7 @@ module_param_named(every_nth, sdebug_every_nth, int, S_IRUGO | S_IWUSR);
>   module_param_named(fake_rw, sdebug_fake_rw, int, S_IRUGO | S_IWUSR);
>   module_param_named(guard, sdebug_guard, uint, S_IRUGO);
>   module_param_named(host_lock, sdebug_host_lock, bool, S_IRUGO | S_IWUSR);
> +module_param_named(host_max_queue, sdebug_host_max_queue, int, S_IRUGO);
>   module_param_string(inq_product, sdebug_inq_product_id,
>   		    sizeof(sdebug_inq_product_id), S_IRUGO | S_IWUSR);
>   module_param_string(inq_rev, sdebug_inq_product_rev,
> @@ -5642,6 +5662,8 @@ MODULE_PARM_DESC(every_nth, "timeout every nth command(def=0)");
>   MODULE_PARM_DESC(fake_rw, "fake reads/writes instead of copying (def=0)");
>   MODULE_PARM_DESC(guard, "protection checksum: 0=crc, 1=ip (def=0)");
>   MODULE_PARM_DESC(host_lock, "host_lock is ignored (def=0)");
> +MODULE_PARM_DESC(host_max_queue,
> +		 "host max # of queued cmds (0 to max(def) [max_queue fixed equal for !0])");
>   MODULE_PARM_DESC(inq_product, "SCSI INQUIRY product string (def=\"scsi_debug\")");
>   MODULE_PARM_DESC(inq_rev, "SCSI INQUIRY revision string (def=\""
>   		 SDEBUG_VERSION "\")");
> @@ -6141,7 +6163,8 @@ static ssize_t max_queue_store(struct device_driver *ddp, const char *buf,
>   	struct sdebug_queue *sqp;
>   
>   	if ((count > 0) && (1 == sscanf(buf, "%d", &n)) && (n > 0) &&
> -	    (n <= SDEBUG_CANQUEUE)) {
> +	    (n <= SDEBUG_CANQUEUE) &&
> +	    (sdebug_host_max_queue == 0)) {
>   		block_unblock_all_queues(true);
>   		k = 0;
>   		for (j = 0, sqp = sdebug_q_arr; j < submit_queues;
> @@ -6164,6 +6187,17 @@ static ssize_t max_queue_store(struct device_driver *ddp, const char *buf,
>   }
>   static DRIVER_ATTR_RW(max_queue);
>   
> +static ssize_t host_max_queue_show(struct device_driver *ddp, char *buf)
> +{
> +	return scnprintf(buf, PAGE_SIZE, "%d\n", sdebug_host_max_queue);
> +}
> +
> +/*
> + * Since this is used for .can_queue, and we get the hc_idx tag from the bitmap
> + * in range [0, sdebug_host_max_queue), we can't change it.
> + */
> +static DRIVER_ATTR_RO(host_max_queue);
> +
>   static ssize_t no_uld_show(struct device_driver *ddp, char *buf)
>   {
>   	return scnprintf(buf, PAGE_SIZE, "%d\n", sdebug_no_uld);
> @@ -6503,6 +6537,7 @@ static struct attribute *sdebug_drv_attrs[] = {
>   	&driver_attr_ptype.attr,
>   	&driver_attr_dsense.attr,
>   	&driver_attr_fake_rw.attr,
> +	&driver_attr_host_max_queue.attr,
>   	&driver_attr_no_lun_0.attr,
>   	&driver_attr_num_tgts.attr,
>   	&driver_attr_dev_size_mb.attr,
> @@ -6619,6 +6654,20 @@ static int __init scsi_debug_init(void)
>   		return -EINVAL;
>   	}
>   
> +	if ((sdebug_host_max_queue > SDEBUG_CANQUEUE) ||
> +	    (sdebug_host_max_queue < 0)) {
> +		pr_err("host_max_queue must be in range [0 %d]\n",
> +		       SDEBUG_CANQUEUE);
> +		return -EINVAL;
> +	}
> +
> +	if (sdebug_host_max_queue &&
> +	    (sdebug_max_queue != sdebug_host_max_queue)) {
> +		sdebug_max_queue = sdebug_host_max_queue;
> +		pr_warn("fixing max submit queue depth to host max queue depth, %d\n",
> +			sdebug_max_queue);
> +	}
> +
>   	sdebug_q_arr = kcalloc(submit_queues, sizeof(struct sdebug_queue),
>   			       GFP_KERNEL);
>   	if (sdebug_q_arr == NULL)
> @@ -7257,7 +7306,10 @@ static int sdebug_driver_probe(struct device *dev)
>   
>   	sdbg_host = to_sdebug_host(dev);
>   
> -	sdebug_driver_template.can_queue = sdebug_max_queue;
> +	if (sdebug_host_max_queue)
> +		sdebug_driver_template.can_queue = sdebug_host_max_queue;
> +	else
> +		sdebug_driver_template.can_queue = sdebug_max_queue;
>   	if (!sdebug_clustering)
>   		sdebug_driver_template.dma_boundary = PAGE_SIZE - 1;
>   
> @@ -7272,9 +7324,13 @@ static int sdebug_driver_probe(struct device *dev)
>   			my_name, submit_queues, nr_cpu_ids);
>   		submit_queues = nr_cpu_ids;
>   	}
> -	/* Decide whether to tell scsi subsystem that we want mq */
> -	/* Following should give the same answer for each host */
> -	hpnt->nr_hw_queues = submit_queues;
> +	/*
> +	 * Decide whether to tell scsi subsystem that we want mq. The
> +	 * following should give the same answer for each host. If the host
> +	 * has a limit of hostwide max commands, then do not set.
> +	 */
> +	if (!sdebug_host_max_queue)
> +		hpnt->nr_hw_queues = submit_queues;
>   
>   	sdbg_host->shost = hpnt;
>   	*((struct sdebug_host_info **)hpnt->hostdata) = sdbg_host;
> 

Re: [PATCH v2 2/2] scsi: scsi_debug: Support hostwide tags

[John Garry]

On 09/07/2020 16:25, Douglas Gilbert wrote:
>>
>> hwq = cpu % queue count
>>
>> If the host max queue param is set non-zero, then the max queue depth is
>> fixed at this value also.
>>
>> If and when hostwide shared tags are supported in blk-mq/scsi mid-layer,
>> then the policy to set nr_hw_queues = 0 for hostwide tags can be revised.
>>
>> Signed-off-by: John Garry <john.garry@huawei.com>
> 
> Acked-by: Douglas Gilbert <dgilbert@interlog.com>
> 
> I have updated this page to reflect this addition:
> http://sg.danny.cz/sg/scsi_debug.html

ok, thanks.

Re: [PATCH v2 0/2] scsi: scsi_debug: Support hostwide tags and a fix

[Martin K. Petersen]

On Thu, 9 Jul 2020 20:23:18 +0800, John Garry wrote:

> This series includes hostwide tags support, so we can mimic some SCSI HBAs,
> like megaraid sas or hisi_sas.
> 
> There is also a fix for an out-of-range module param.
> 
> Differences to v1:
> - add Doug's Ack for patch 1/2
> - sort params alphabetically
> - fix max queue at host max queue (when non-zero)
> - drop host max queue file write permission
> 
> [...]

Applied to 5.9/scsi-queue, thanks!

[1/2] scsi: scsi_debug: Add check for sdebug_max_queue during module init
      https://git.kernel.org/mkp/scsi/c/c87bf24cfb60
[2/2] scsi: scsi_debug: Support hostwide tags
      https://git.kernel.org/mkp/scsi/c/c10fa55f5e7a

-- 
Martin K. Petersen	Oracle Linux Engineering