Message-ID: <DM6PR04MB657590BD9CAB3BAE180C7AE5FC699@DM6PR04MB6575.namprd04.prod.outlook.com>
Date:   Thu, 18 Mar 2021 08:04:02 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Can Guo <cang@...eaurora.org>
CC:     "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Bart Van Assche <bvanassche@....org>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        Daejun Park <daejun7.park@...sung.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        Zang Leigang <zangleigang@...ilicon.com>,
        Avi Shchislowski <Avi.Shchislowski@....com>,
        Bean Huo <beanhuo@...ron.com>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>
Subject: RE: [PATCH v5 06/10] scsi: ufshpb: Add hpb dev reset response

> On 2021-03-17 23:46, Avri Altman wrote:
> >> >> >> >>
> >> >> >> >> Just curious, directly doing below things inside ufshpb_rsp_upiu()
> >> >> >> >> does
> >> >> >> >> not
> >> >> >> >> seem a problem to me, does this really deserve a separate work?
> >> >> >> > I don't know, I never even consider of doing this.
> >> >> >> > The active region list may contain up to few thousands of regions -
> >> >> >> > It is not rare to see configurations that covers the entire device.
> >> >> >> >
> >> >> >>
> >> >> >> Yes, true, it can be a huge list. But what does the ops
> >> >> >> "HPB_RSP_DEV_RESET"
> >> >> >> really mean? The specs says "Device reset HPB Regions information",
> >> >> >> but
> >> >> >> I
> >> >> >> don't know what is really happening. Could you please elaborate?
> >> >> > It means that the device informs the host that the L2P cache is no
> >> >> > longer valid.
> >> >> > The spec doesn't say what to do in that case.
> >> >>
> >> >> Then it means that all the clean (without DIRTY flag set) HPB entries
> >> >> (ppns)
> >> >> in active rgns in host memory side may not be valid to the device
> >> >> anymore.
> >> >> Please correct me if I am wrong.
> >> >>
> >> >> > We thought that in host mode, it make sense to update all the active
> >> >> > regions.
> >> >>
> >> >> But current logic does not set the state of the sub-regions (in active
> >> >> regions) to
> >> >> INVALID, it only marks all active regions as UPDATE.
> >> >>
> >> >> Although one of subsequent read cmds shall put the sub-region back to
> >> >> activate_list,
> >> >> ufshpb_test_ppn_dirty() can still return false, thus these read cmds
> >> >> still think the
> >> >> ppns are valid and they shall move forward to send HPB Write Buffer
> >> >> (buffer id = 0x2,
> >> >> in case of HPB2.0) and HPB Read cmds.
> >> >>
> >> >> HPB Read cmds with invalid ppns will be treated as normal Read cmds by
> >> >> device as the
> >> >> specs says, but what would happen to HPB Write Buffer cmds (buffer id
> >> >> =
> >> >> 0x2, in case
> >> >> of HPB2.0) with invalid ppns? Can this be a real problem?
> >> > No need to control the ppn dirty / invalid state for this case.
> >> > The device send device reset so it is aware that all the L2P cache is
> >> > invalid.
> >> > Any HPB_READ is treated like normal READ10.
> >> >
> >> > Only once HPB-READ-BUFFER is completed,
> >> > the device will relate back to the physical address.
> >>
> >> What about HPB-WRITE-BUFFER (buffer id = 0x2) cmds?
> > Same.
> > Oper 0x2 is a relative simple case.
> > The device is expected to manage some versioning framework not to be
> > "fooled" by erroneous ppn.
> > There are some more challenging races that the device should meet.
> >
> 
> But I don't find the handling w.r.t this scenario on HPB2.0 specs -
> how would the device re-act/respond to HPB-WRITE-BUFFER cmds with
> invalid HPB entries? Could you please point me to relevant
> section/paragraph?
The spec does not handle that.
HPB-WRITE-BUFFER 0x2 is not a stand-alone command, it always tagged to a HPB-READ command.
It is up to the device to handle invalid ppn and always return the correct data.
The expected performance in that case is like a regular READ10.

Thanks,
Avri 

> 
> Thanks,
> Can Guo.
> 
> > Thanks,
> > Avri
> >>
> >> Thanks,
> >> Can Guo.
> >>
> >> >
> >> >>
> >> >> >
> >> >> > I think I will go with your suggestion.
> >> >> > Effectively, in host mode, since it is deactivating "cold" regions,
> >> >> > the lru list is kept relatively small, and contains only "hot" regions.
> >> >>
> >> >> hmm... I don't really have a idea on this, please go with whatever you
> >> >> and Daejun think is fine here.
> >> > I will take your advice and remove the worker.
> >> >
> >> >
> >> > Thanks,
> >> > Avri
> >> >
> >> >>
> >> >> Thanks,
> >> >> Can Guo.
> >> >>
> >> >> >
> >> >> > Thanks,
> >> >> > Avri
> >> >> >
> >> >> >>
> >> >> >> Thanks,
> >> >> >> Can Guo.
> >> >> >>
> >> >> >> > But yes, I can do that.
> >> >> >> > Better to get ack from Daejun first.
> >> >> >> >
> >> >> >> > Thanks,
> >> >> >> > Avri
> >> >> >> >
> >> >> >> >>
> >> >> >> >> Thanks,
> >> >> >> >> Can Guo.
> >> >> >> >>
> >> >> >> >> > +{
> >> >> >> >> > +     struct ufshpb_lu *hpb;
> >> >> >> >> > +     struct victim_select_info *lru_info;
> >> >> >> >> > +     struct ufshpb_region *rgn;
> >> >> >> >> > +     unsigned long flags;
> >> >> >> >> > +
> >> >> >> >> > +     hpb = container_of(work, struct ufshpb_lu,
> >> >> ufshpb_lun_reset_work);
> >> >> >> >> > +
> >> >> >> >> > +     lru_info = &hpb->lru_info;
> >> >> >> >> > +
> >> >> >> >> > +     spin_lock_irqsave(&hpb->rgn_state_lock, flags);
> >> >> >> >> > +
> >> >> >> >> > +     list_for_each_entry(rgn, &lru_info->lh_lru_rgn, list_lru_rgn)
> >> >> >> >> > +             set_bit(RGN_FLAG_UPDATE, &rgn->rgn_flags);
> >> >> >> >> > +
> >> >> >> >> > +     spin_unlock_irqrestore(&hpb->rgn_state_lock, flags);
> >> >> >> >> > +}
> >> >> >> >> > +
> >> >> >> >> >  static void ufshpb_normalization_work_handler(struct
> work_struct
> >> >> >> >> > *work)
> >> >> >> >> >  {
> >> >> >> >> >       struct ufshpb_lu *hpb;
> >> >> >> >> > @@ -1798,6 +1832,8 @@ static int
> ufshpb_alloc_region_tbl(struct
> >> >> >> >> > ufs_hba *hba, struct ufshpb_lu *hpb)
> >> >> >> >> >               } else {
> >> >> >> >> >                       rgn->rgn_state = HPB_RGN_INACTIVE;
> >> >> >> >> >               }
> >> >> >> >> > +
> >> >> >> >> > +             rgn->rgn_flags = 0;
> >> >> >> >> >       }
> >> >> >> >> >
> >> >> >> >> >       return 0;
> >> >> >> >> > @@ -2012,9 +2048,12 @@ static int ufshpb_lu_hpb_init(struct
> >> >> ufs_hba
> >> >> >> >> > *hba, struct ufshpb_lu *hpb)
> >> >> >> >> >       INIT_LIST_HEAD(&hpb->list_hpb_lu);
> >> >> >> >> >
> >> >> >> >> >       INIT_WORK(&hpb->map_work, ufshpb_map_work_handler);
> >> >> >> >> > -     if (hpb->is_hcm)
> >> >> >> >> > +     if (hpb->is_hcm) {
> >> >> >> >> >               INIT_WORK(&hpb->ufshpb_normalization_work,
> >> >> >> >> >                         ufshpb_normalization_work_handler);
> >> >> >> >> > +             INIT_WORK(&hpb->ufshpb_lun_reset_work,
> >> >> >> >> > +                       ufshpb_reset_work_handler);
> >> >> >> >> > +     }
> >> >> >> >> >
> >> >> >> >> >       hpb->map_req_cache =
> >> kmem_cache_create("ufshpb_req_cache",
> >> >> >> >> >                         sizeof(struct ufshpb_req), 0, 0, NULL);
> >> >> >> >> > @@ -2114,8 +2153,10 @@ static void
> >> ufshpb_discard_rsp_lists(struct
> >> >> >> >> > ufshpb_lu *hpb)
> >> >> >> >> >
> >> >> >> >> >  static void ufshpb_cancel_jobs(struct ufshpb_lu *hpb)
> >> >> >> >> >  {
> >> >> >> >> > -     if (hpb->is_hcm)
> >> >> >> >> > +     if (hpb->is_hcm) {
> >> >> >> >> > +             cancel_work_sync(&hpb->ufshpb_lun_reset_work);
> >> >> >> >> >               cancel_work_sync(&hpb->ufshpb_normalization_work);
> >> >> >> >> > +     }
> >> >> >> >> >       cancel_work_sync(&hpb->map_work);
> >> >> >> >> >  }
> >> >> >> >> >
> >> >> >> >> > diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
> >> >> >> >> > index 84598a317897..37c1b0ea0c0a 100644
> >> >> >> >> > --- a/drivers/scsi/ufs/ufshpb.h
> >> >> >> >> > +++ b/drivers/scsi/ufs/ufshpb.h
> >> >> >> >> > @@ -121,6 +121,7 @@ struct ufshpb_region {
> >> >> >> >> >       struct list_head list_lru_rgn;
> >> >> >> >> >       unsigned long rgn_flags;
> >> >> >> >> >  #define RGN_FLAG_DIRTY 0
> >> >> >> >> > +#define RGN_FLAG_UPDATE 1
> >> >> >> >> >
> >> >> >> >> >       /* region reads - for host mode */
> >> >> >> >> >       spinlock_t rgn_lock;
> >> >> >> >> > @@ -217,6 +218,7 @@ struct ufshpb_lu {
> >> >> >> >> >       /* for selecting victim */
> >> >> >> >> >       struct victim_select_info lru_info;
> >> >> >> >> >       struct work_struct ufshpb_normalization_work;
> >> >> >> >> > +     struct work_struct ufshpb_lun_reset_work;
> >> >> >> >> >
> >> >> >> >> >       /* pinned region information */
> >> >> >> >> >       u32 lu_pinned_start;

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