RE: [RFC/RFT PATCH] scsi: pm8001: Expose HW queues for pm80xx hw

[Viswas.G]

Thanks Johns. 

We could see a kernel crash while testing this patch.

[  246.724632] scsi host10: pm80xx
[  248.005258] sas: Enter sas_scsi_recover_host busy: 0 failed: 0
[  248.168973] BUG: kernel NULL pointer dereference, address: 0000000000000110
[  248.175926] #PF: supervisor read access in kernel mode
[  248.181065] #PF: error_code(0x0000) - not-present page
[  248.186196] PGD 0 P4D 0
[  248.188736] Oops: 0000 [#1] SMP PTI
[  248.192230] CPU: 10 PID: 77 Comm: kworker/u26:2 Kdump: loaded Tainted: G S         OE     5.11.0-rc3 #2
[  248.201614] Hardware name: Supermicro Super Server/X10DRi-LN4+, BIOS 3.1 06/08/2018
[  248.209258] Workqueue: events_unbound async_run_entry_fn
[  248.214571] RIP: 0010:pm80xx_chip_sata_req+0x7f/0x5e0 [pm80xx]
[  248.220413] Code: c1 7c c1 e9 03 4d 8b ac 24 80 01 00 00 48 c7 44 24 14 00 00 00 00 89 04 24 31 c0 48 c7 84 24 88 00 00 00 00 00 00 00 f3 48 ab <48> 8b ba 10 01 00 00 e8 35 35 c6 ef c1 e8 10 89 44 24 04 0f b6 43
[  248.239157] RSP: 0018:ffffb98d834979f0 EFLAGS: 00010046
[  248.244384] RAX: 0000000000000000 RBX: ffff9523c321c000 RCX: 0000000000000000
[  248.251516] RDX: 0000000000000000 RSI: ffff952450720048 RDI: ffffb98d83497a80
[  248.258641] RBP: ffff9523c7420000 R08: 0000000000000100 R09: 0000000000000001
[  248.265764] R10: 0000000000000001 R11: ffff9523c9e40000 R12: ffff9523ca1c3600
[  248.272887] R13: ffff9523c9e40000 R14: ffffb98d83497a04 R15: ffff952450720048
[  248.280013] FS:  0000000000000000(0000) GS:ffff9527afd00000(0000) knlGS:0000000000000000
[  248.288090] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  248.293826] CR2: 0000000000000110 CR3: 000000029ac10001 CR4: 00000000001706e0
[  248.300952] Call Trace:
[  248.303402]  pm8001_task_exec.isra.9+0x2a4/0x460 [pm80xx]
[  248.308805]  sas_ata_qc_issue+0x187/0x220 [libsas]
[  248.313607]  ata_qc_issue+0x107/0x1e0 [libata]
[  248.318069]  ata_exec_internal_sg+0x2c8/0x580 [libata]
[  248.323217]  ata_exec_internal+0x5f/0x90 [libata]
[  248.327931]  ata_dev_read_id+0x306/0x480 [libata]
[  248.332647]  ata_eh_recover+0x7ea/0x12a0 [libata]
[  248.337369]  ? vprintk_emit+0x114/0x220
[  248.341208]  ? sas_ata_sched_eh+0x60/0x60 [libsas]
[  248.346002]  ? sas_ata_prereset+0x50/0x50 [libsas]
[  248.350795]  ? printk+0x58/0x6f
[  248.353941]  ? sas_ata_sched_eh+0x60/0x60 [libsas]
[  248.358733]  ? sas_ata_prereset+0x50/0x50 [libsas]
[  248.363525]  ata_do_eh+0x40/0xb0 [libata]
[  248.367556]  ata_scsi_port_error_handler+0x354/0x770 [libata]
[  248.373318]  async_sas_ata_eh+0x44/0x7b [libsas]
[  248.377938]  async_run_entry_fn+0x39/0x160
[  248.382040]  process_one_work+0x1cb/0x360
[  248.386050]  worker_thread+0x30/0x370
[  248.389706]  ? processe_work+0x360/0x360
[  248.393884]  kthread+0x116/0x130
[  248.397116]  ? kthread_park+0x80/0x80
[  248.400773]  ret_from_fork+0x22/0x30
[  248.404355] Modules linked in: pm80xx(OE) libsas scsi_transport_sas xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 nft_compat nft_counter nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink tun bridge stp llc rfkill sunrpc vfat fat intel_rapl_msr intel_rapl_common sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass joydev crct10dif_pclmul crc32_pclmul ghash_clmulni_intel ipmi_ssif iTCO_wdt iTCO_vendor_support mei_me rapl i2c_i801 intel_cstate mei acpi_ipmi lpc_ich intel_uncore pcspkr ipmi_si i2c_smbus ipmi_devintf ipmi_msghandler acpi_power_meter acpi_pad ioatdma ip_tables xfs libcrc32c sr_mod sd_mod cdrom t10_pi sg ast drm_vram_helper drm_kms_helper syscopyarea igb sysfillrect sysimgblt fb_sys_fops drm_ttm_helper ttm ahci libahci dca drm crc32c_intel libata i2c_algo_bit wmi dm_mirror dm_region_hash dm_log dm_mod fuse
[  248.483431] CR2: 0000000000000110
[    0.000000] Linux version 5.11.0-rc3 (root@localhost.localdomain) (gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), GNU ld version 2.30-79.el8) #2 SMP Mon Jan 25 23:56:12 IST 2021
[    0.000000] Command line: elfcorehr=0x45000000 BOOT_IMAGE=(hd14,gpt2)/vmlinuz-5.11.0-rc3 ro resume=/dev/mapper/rhel-swap rhgb console=ttyS1,115200 loglevel=7 irqpoll nr_cpus=1 reset_devices cgroup_disable=memory mce=off numa=off udev.children-max=2 panic=10 rootflags=nofail acpi_no_memhotplug transparent_hugepage=never nokaslr novmcoredd hest_disable disable_cpu_apicid=0


> -----Original Message-----
> From: John Garry <john.garry@xxxxxxxxxx>
> Sent: Tuesday, January 5, 2021 4:47 PM
> To: jejb@xxxxxxxxxxxxx; martin.petersen@xxxxxxxxxx;
> akshatzen@xxxxxxxxxx; Viswas G - I30667 <Viswas.G@xxxxxxxxxxxxx>;
> Ruksar Devadi - I52327 <Ruksar.devadi@xxxxxxxxxxxxx>;
> radha@xxxxxxxxxx; bjashnani@xxxxxxxxxx; vishakhavc@xxxxxxxxxx;
> jinpu.wang@xxxxxxxxxxxxxxx; Ashokkumar N - X53535
> <Ashokkumar.N@xxxxxxxxxxxxx>
> Cc: linux-scsi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; hare@xxxxxxx;
> kashyap.desai@xxxxxxxxxxxx; ming.lei@xxxxxxxxxx; John Garry
> <john.garry@xxxxxxxxxx>
> Subject: [RFC/RFT PATCH] scsi: pm8001: Expose HW queues for pm80xx hw
> 
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the
> content is safe
> 
> In commit 05c6c029a44d ("scsi: pm80xx: Increase number of supported
> queues"), support for 80xx chip was improved by enabling multiple HW
> queues.
> 
> In this, like other SCSI MQ HBA drivers, the HW queues were not exposed to
> upper layer, and instead the driver managed the queues internally.
> 
> However, this management duplicates blk-mq code. In addition, the HW
> queue management is sub-optimal for a system where the number of CPUs
> exceeds the HW queues - this is because queues are selected in a round-
> robin fashion, when it would be better to make adjacent CPUs submit on the
> same queue. And finally, the affinity of the completion queue interrupts is
> not set to mirror the cpu<->HQ queue mapping, which is suboptimal.
> 
> As such, for when MSIX is supported, expose HW queues to upper layer. Flag
> PCI_IRQ_AFFINITY is set for allocating the MSIX vectors to automatically
> assign affinity for the completion queue interrupts.
> 
> Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
> 
> ---
> I sent as an RFC/RFT as I have no HW to test. In addition, since HW queue
> #0 is used always for internal commands (like in send_task_abort()), if all
> CPUs associated with HW queue #0 are offlined, the interrupt for that queue
> will be shutdown, and no CPUs would be available to service any internal
> commands completion. To solve that, we need [0] merged first and switch
> over to use the new API. But we can still test performance in the meantime.
> 
> I assume someone else is making the change to use the request tag for IO
> tag management.
> 
> [0] https://lore.kernel.org/linux-scsi/47ba045e-a490-198b-1744-
> 529f97192d3b@xxxxxxx/
> 
> diff --git a/drivers/scsi/pm8001/pm8001_init.c
> b/drivers/scsi/pm8001/pm8001_init.c
> index ee2de177d0d0..73479803a23e 100644
> --- a/drivers/scsi/pm8001/pm8001_init.c
> +++ b/drivers/scsi/pm8001/pm8001_init.c
> @@ -81,6 +81,15 @@ LIST_HEAD(hba_list);
> 
>  struct workqueue_struct *pm8001_wq;
> 
> +static int pm8001_map_queues(struct Scsi_Host *shost) {
> +       struct sas_ha_struct *sha = SHOST_TO_SAS_HA(shost);
> +       struct pm8001_hba_info *pm8001_ha = sha->lldd_ha;
> +       struct blk_mq_queue_map *qmap =
> +&shost->tag_set.map[HCTX_TYPE_DEFAULT];
> +
> +       return blk_mq_pci_map_queues(qmap, pm8001_ha->pdev, 0); }
> +
>  /*
>   * The main structure which LLDD must register for scsi core.
>   */
> @@ -106,6 +115,7 @@ static struct scsi_host_template pm8001_sht = {
> #ifdef CONFIG_COMPAT
>         .compat_ioctl           = sas_ioctl,
>  #endif
> +       .map_queues                     = pm8001_map_queues,
>         .shost_attrs            = pm8001_host_attrs,
>         .track_queue_depth      = 1,
>  };
> @@ -923,9 +933,8 @@ static int pm8001_configure_phy_settings(struct
> pm8001_hba_info *pm8001_ha)  static u32 pm8001_setup_msix(struct
> pm8001_hba_info *pm8001_ha)  {
>         u32 number_of_intr;
> -       int rc, cpu_online_count;
> +       int rc;
>         unsigned int allocated_irq_vectors;
> -
>         /* SPCv controllers supports 64 msi-x */
>         if (pm8001_ha->chip_id == chip_8001) {
>                 number_of_intr = 1;
> @@ -933,16 +942,15 @@ static u32 pm8001_setup_msix(struct
> pm8001_hba_info *pm8001_ha)
>                 number_of_intr = PM8001_MAX_MSIX_VEC;
>         }
> 
> -       cpu_online_count = num_online_cpus();
> -       number_of_intr = min_t(int, cpu_online_count, number_of_intr);
> -       rc = pci_alloc_irq_vectors(pm8001_ha->pdev, number_of_intr,
> -                       number_of_intr, PCI_IRQ_MSIX);
> +       /* Use default affinity descriptor, which spreads *all* vectors */
> +       rc = pci_alloc_irq_vectors(pm8001_ha->pdev, 1,
> +                       number_of_intr, PCI_IRQ_MSIX |
> + PCI_IRQ_AFFINITY);
>         allocated_irq_vectors = rc;
>         if (rc < 0)
>                 return rc;
> 
>         /* Assigns the number of interrupts */
> -       number_of_intr = min_t(int, allocated_irq_vectors, number_of_intr);
> +       number_of_intr = allocated_irq_vectors;
>         pm8001_ha->number_of_intr = number_of_intr;
> 
>         /* Maximum queue number updating in HBA structure */ @@ -1113,6
> +1121,16 @@ static int pm8001_pci_probe(struct pci_dev *pdev,
>         if (rc)
>                 goto err_out_enable;
> 
> +       if (pm8001_ha->number_of_intr > 1) {
> +               shost->nr_hw_queues = pm8001_ha->number_of_intr;
> +               /*
> +                * For now, ensure we're not sent too many commands by setting
> +                * host_tagset. This is also required if we start using request
> +                * tag.
> +                */
> +               shost->host_tagset = 1;
> +       }
> +
>         rc = scsi_add_host(shost, &pdev->dev);
>         if (rc)
>                 goto err_out_ha_free;
> diff --git a/drivers/scsi/pm8001/pm8001_sas.h
> b/drivers/scsi/pm8001/pm8001_sas.h
> index f2c8cbad3853..74bc6fed693e 100644
> --- a/drivers/scsi/pm8001/pm8001_sas.h
> +++ b/drivers/scsi/pm8001/pm8001_sas.h
> @@ -55,6 +55,8 @@
>  #include <scsi/scsi_tcq.h>
>  #include <scsi/sas_ata.h>
>  #include <linux/atomic.h>
> +#include <linux/blk-mq.h>
> +#include <linux/blk-mq-pci.h>
>  #include "pm8001_defs.h"
> 
>  #define DRV_NAME               "pm80xx"
> diff --git a/drivers/scsi/pm8001/pm80xx_hwi.c
> b/drivers/scsi/pm8001/pm80xx_hwi.c
> index 6772b0924dac..31d65ce91e7d 100644
> --- a/drivers/scsi/pm8001/pm80xx_hwi.c
> +++ b/drivers/scsi/pm8001/pm80xx_hwi.c
> @@ -4299,12 +4299,13 @@ static int pm80xx_chip_ssp_io_req(struct
> pm8001_hba_info *pm8001_ha,
>         struct domain_device *dev = task->dev;
>         struct pm8001_device *pm8001_dev = dev->lldd_dev;
>         struct ssp_ini_io_start_req ssp_cmd;
> +       struct scsi_cmnd *scmd = task->uldd_task;
>         u32 tag = ccb->ccb_tag;
>         int ret;
>         u64 phys_addr, start_addr, end_addr;
>         u32 end_addr_high, end_addr_low;
>         struct inbound_queue_table *circularQ;
> -       u32 q_index, cpu_id;
> +       u32 blk_tag, q_index;
>         u32 opc = OPC_INB_SSPINIIOSTART;
>         memset(&ssp_cmd, 0, sizeof(ssp_cmd));
>         memcpy(ssp_cmd.ssp_iu.lun, task->ssp_task.LUN, 8); @@ -4323,8
> +4324,8 @@ static int pm80xx_chip_ssp_io_req(struct pm8001_hba_info
> *pm8001_ha,
>         ssp_cmd.ssp_iu.efb_prio_attr |= (task->ssp_task.task_attr & 7);
>         memcpy(ssp_cmd.ssp_iu.cdb, task->ssp_task.cmd->cmnd,
>                        task->ssp_task.cmd->cmd_len);
> -       cpu_id = smp_processor_id();
> -       q_index = (u32) (cpu_id) % (pm8001_ha->max_q_num);
> +       blk_tag = blk_mq_unique_tag(scmd->request);
> +       q_index = blk_mq_unique_tag_to_hwq(blk_tag);
>         circularQ = &pm8001_ha->inbnd_q_tbl[q_index];
> 
>         /* Check if encryption is set */ @@ -4446,9 +4447,11 @@ static int
> pm80xx_chip_sata_req(struct pm8001_hba_info *pm8001_ha,
>         struct sas_task *task = ccb->task;
>         struct domain_device *dev = task->dev;
>         struct pm8001_device *pm8001_ha_dev = dev->lldd_dev;
> +       struct ata_queued_cmd *qc = task->uldd_task;
> +       struct scsi_cmnd *scmd = qc->scsicmd;
>         u32 tag = ccb->ccb_tag;
>         int ret;
> -       u32 q_index, cpu_id;
> +       u32 q_index, blk_tag;
>         struct sata_start_req sata_cmd;
>         u32 hdr_tag, ncg_tag = 0;
>         u64 phys_addr, start_addr, end_addr; @@ -4459,8 +4462,9 @@ static int
> pm80xx_chip_sata_req(struct pm8001_hba_info *pm8001_ha,
>         unsigned long flags;
>         u32 opc = OPC_INB_SATA_HOST_OPSTART;
>         memset(&sata_cmd, 0, sizeof(sata_cmd));
> -       cpu_id = smp_processor_id();
> -       q_index = (u32) (cpu_id) % (pm8001_ha->max_q_num);
> +
> +       blk_tag = blk_mq_unique_tag(scmd->request);

Here the scsi command is NULL.

  if(scmd) {
                blk_tag = blk_mq_unique_tag(scmd->request);
                q_index = blk_mq_unique_tag_to_hwq(blk_tag);
        } else {
                q_index = 0;
  }

With this change, we have started our testing. We will update you the result soon.

> +       q_index = blk_mq_unique_tag_to_hwq(blk_tag);
>         circularQ = &pm8001_ha->inbnd_q_tbl[q_index];
> 
>         if (task->data_dir == DMA_NONE) {
> --
> 2.26.2