[U-Boot] [PATCH v2 2/3] efi_loader: enumerate disk devices every time

AKASHI Takahiro
2019-01-23T08:12:20Z

Alex,

On Tue, Jan 22, 2019 at 10:08:53AM +0100, Alexander Graf wrote:
>
>
> On 22.01.19 09:29, AKASHI Takahiro wrote:
> > Alex, Simon,
> >
> > Apologies for my slow response on this matter,
> >
> > On Fri, Jan 11, 2019 at 08:57:05AM +0100, Alexander Graf wrote:
> >>
> >>
> >> On 11.01.19 05:29, AKASHI Takahiro wrote:
> >>> Alex, Heinrich and Simon,
> >>>
> >>> Thank you for your comments, they are all valuable but also make me
> >>> confused as different people have different requirements :)
> >>> I'm not sure that all of us share the same *ultimate* goal here.
> >>
> >> The shared ultimate goal is to "merge" (as Simon put it) dm and efi objects.
> >
> > I don't still understand what "merge" means very well.
>
> It basically means that "struct efi_object" moves into "struct udevice".
> Every udevice instance of type UCLASS_BLK would expose the block and
> device_path protocols.
>
> This will be a slightly bigger rework, but eventually allows us to
> basically get rid of efi_init_obj_list() I think.
>
> >
> >> But we have this annoying interim state where we would lose a few boards
> >> because they haven't been converted to DM. That's what keeps us from it.
> >>
> >> I think what this discussion boils down to is that someone needs to
> >> start prototyping the DM/EFI integration. Start off with a simple
> >> subsystem, like BLK.
> >
> > Even in the current implementation,
> > * UEFI disk is implemented using UCLASS_BLK devices
> > (We can ignore !CONFIG_BLK case now as we have agreed.)
> > * UEFI-specific block device can be seen as UCLASS_BLK/IF_TYPE_EFI
> >
> > So how essentially different is the *ultimate* goal from the current form
> > regarding block devices?
>
> The ultimate goal is that efi_disk_register() and efi_obj_list disappear.
>
> Functionality wise we should be 100% identical to today, so all test
> cases would still apply the same way as they do now. This is purely
> internal rework, nothing visible to UEFI payloads.
>
> > In order to identify UEFI disks with u-boot devices transparently, we will
> > have to have some sort of *hook* (or hotplug in Alex's language?), either
> > in create_block_devices or bind/probe? I don't know, but Simon seems
> > to be in denial about this idea.
>
> Well, if a udevice *is* an efi device, we no longer need hooks. The
> object list would simply change.
>
> We may still need to have event notifications at that stage, but that's
> a different story.
>
> As transitioning period, we could probably implement 2 efi object roots:
> efi_obj_list as well as the udevice based one. Every piece of code that
> iterates through devices then just iterates over both. That way we
> should be able to slowly move devices from the old object model to the
> new one.
>
> >> Then provide a DM path and have a non-DM fallback
> >> still in its own source file that also provides EFI BLK devices.
> >> Eventually we just remove the latter.
> >>
> >> That way we can then work on getting hotplug working in the DM path,
> >> which is the one we want anyway. For non-DM, you simply miss out on that
> >> amazing new feature, but we don't regress users.
> >>
> >>> So, first, let me reply to each of your comments.
> >>> Through this process, I hope we will have better understandings
> >>> of long-term solution as well as a tentative fix.
> >>>
> >>> On Thu, Jan 10, 2019 at 10:22:04AM +0100, Alexander Graf wrote:
> >>>>
> >>>>
> >>>>> Am 10.01.2019 um 10:16 schrieb AKASHI Takahiro <takahiro.akashi@linaro.org>:
> >>>>>
> >>>>>> On Thu, Jan 10, 2019 at 09:15:36AM +0100, Alexander Graf wrote:
> >>>>>>
> >>>>>>
> >>>>>>>> Am 10.01.2019 um 09:02 schrieb AKASHI Takahiro <takahiro.akashi@linaro.org>:
> >>>>>>>>
> >>>>>>>> On Thu, Jan 10, 2019 at 08:30:13AM +0100, Alexander Graf wrote:
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>> On 10.01.19 08:26, AKASHI Takahiro wrote:
> >>>>>>>>> Alex,
> >>>>>>>>>
> >>>>>>>>>> On Thu, Jan 10, 2019 at 07:21:12AM +0100, Alexander Graf wrote:
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>> On 10.01.19 03:13, AKASHI Takahiro wrote:
> >>>>>>>>>>> Alex,
> >>>>>>>>>>>
> >>>>>>>>>>>> On Wed, Jan 09, 2019 at 10:06:16AM +0100, Alexander Graf wrote:
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>> On 13.12.18 08:58, AKASHI Takahiro wrote:
> >>>>>>>>>>>>> Heinrich,
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>>> On Tue, Dec 11, 2018 at 08:55:41PM +0100, Heinrich Schuchardt wrote:
> >>>>>>>>>>>>>>> On 11/15/18 5:58 AM, AKASHI Takahiro wrote:
> >>>>>>>>>>>>>>> Currently, efi_init_obj_list() scan disk devices only once, and never
> >>>>>>>>>>>>>>> change a list of efi disk devices. This will possibly result in failing
> >>>>>>>>>>>>>>> to find a removable storage which may be added later on. See [1].
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> In this patch, called is efi_disk_update() which is responsible for
> >>>>>>>>>>>>>>> re-scanning UCLASS_BLK devices and removing/adding efi disks if necessary.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> For example,
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> => efishell devices
> >>>>>>>>>>>>>>> Scanning disk pci_mmc.blk...
> >>>>>>>>>>>>>>> Found 3 disks
> >>>>>>>>>>>>>>> Device Name
> >>>>>>>>>>>>>>> ============================================
> >>>>>>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)
> >>>>>>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)
> >>>>>>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)/HD(2,MBR,0x086246ba,0x40800,0x3f800)
> >>>>>>>>>>>>>>> => usb start
> >>>>>>>>>>>>>>> starting USB...
> >>>>>>>>>>>>>>> USB0: USB EHCI 1.00
> >>>>>>>>>>>>>>> scanning bus 0 for devices... 3 USB Device(s) found
> >>>>>>>>>>>>>>> scanning usb for storage devices... 1 Storage Device(s) found
> >>>>>>>>>>>>>>> => efishell devices
> >>>>>>>>>>>>>>> Scanning disk usb_mass_storage.lun0...
> >>>>>>>>>>>>>>> Device Name
> >>>>>>>>>>>>>>> ============================================
> >>>>>>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)
> >>>>>>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)
> >>>>>>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/SD(0)/SD(0)/HD(2,MBR,0x086246ba,0x40800,0x3f800)
> >>>>>>>>>>>>>>> /VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b)/USBClass(0,0,9,0,1)/USBClass(46f4,1,0,0,0)/HD(1,0x01,0,0x40,0x14fe4c)
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Without this patch, the last device, USB mass storage, won't show up.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> [1] https://lists.denx.de/pipermail/u-boot/2018-October/345307.html
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> Why should we try to fix something in the EFI subsystems that goes wrong
> >>>>>>>>>>>>>> in the handling of device enumeration.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> No.
> >>>>>>>>>>>>> This is a natural result from how efi disks are currently implemented on u-boot.
> >>>>>>>>>>>>> Do you want to totally re-write/re-implement efi disks?
> >>>>>>>>>>>>
> >>>>>>>>>>>> Could we just make this event based for now? Call a hook from the
> >>>>>>>>>>>> storage dm subsystem when a new u-boot block device gets created to
> >>>>>>>>>>>> issue a sync of that in the efi subsystem?
> >>>>>>>>>>>
> >>>>>>>>>>> If I correctly understand you, your suggestion here corresponds
> >>>>>>>>>>> with my proposal#3 in [1] while my current approach is #2.
> >>>>>>>>>>>
> >>>>>>>>>>> [1] https://lists.denx.de/pipermail/u-boot/2018-October/345307.html
> >>>>>>>>>>
> >>>>>>>>>> Yes, I think so.
> >>>>>>>>>>
> >>>>>>>>>>> So we will call, say, efi_disk_create(struct udevice *) in
> >>>>>>>>>>> blk_create_device() and efi_dsik_delete() in blk_unbind_all().
> >>>>>>>>>>
> >>>>>>>>>> I would prefer if we didn't call them directly, but through an event
> >>>>>>>>>> mechanism. So the efi_disk subsystem registers an event with the dm
> >>>>>>>>>> block subsystem and that will just call all events when block devices
> >>>>>>>>>> get created which will automatically also include the efi disk creation
> >>>>>>>>>> callback. Same for reverse.
> >>>>>>>>>
> >>>>>>>>> Do you mean efi event by "event?"
> >>>>>>>>> (I don't think there is any generic event interface on DM side.)
> >>>>>>>>>
> >>>>>>>>> Whatever an "event" is or whether we call efi_disk_create() directly
> >>>>>>>>> or indirectly via an event, there is one (big?) issue in this approach
> >>>>>>>>> (while I've almost finished prototyping):
> >>>>>>>>>
> >>>>>>>>> We cannot call efi_disk_create() within blk_create_device() because
> >>>>>>>>> some data fields of struct blk_desc, which are to be used by efi disk,
> >>>>>>>>> are initialized *after* blk_create_device() in driver side.
> >>>>>>>>>
> >>>>>>>>> So we need to add a hook at/after every occurrence of blk_create_device()
> >>>>>>>>> on driver side. For example,
> >>>>>>>>>
> >>>>>>>>> === drivers/scsi/scsi.c ===
> >>>>>>>>> int do_scsi_scan_one(struct udevice *dev, int id, int lun, bool verbose)
> >>>>>>>>> {
> >>>>>>>>> ...
> >>>>>>>>> ret = blk_create_devicef(dev, "scsi_blk", str, IF_TYPE_SCSI, -1,
> >>>>>>>>> bd.blksz, bd.lba, &bdev);
> >>>>>>>>> ...
> >>>>>>>>> bdesc = dev_get_uclass_platdata(bdev);
> >>>>>>>>> bdesc->target = id;
> >>>>>>>>> bdesc->lun = lun;
> >>>>>>>>> ...
> >>>>>>>>>
> >>>>>>>>> /*
> >>>>>>>>> * We need have efi_disk_create() called here because bdesc->target
> >>>>>>>>> * and lun will be used by dp helpers in efi_disk_add_dev().
> >>>>>>>>> */
> >>>>>>>>> efi_disk_create(bdev);
> >>>>>>>>> }
> >>>>>>>>>
> >>>>>>>>> int scsi_scan_dev(struct udevice *dev, bool verbose)
> >>>>>>>>> {
> >>>>>>>>> for (i = 0; i < uc_plat->max_id; i++)
> >>>>>>>>> for (lun = 0; lun < uc_plat->max_lun; lun++)
> >>>>>>>>> do_scsi_scan_one(dev, i, lun, verbose);
> >>>>>>>>> ...
> >>>>>>>>> }
> >>>>>>>>>
> >>>>>>>>> int scsi_scan(bool verbose)
> >>>>>>>>> {
> >>>>>>>>> ret = uclass_get(UCLASS_SCSI, &uc);
> >>>>>>>>> ...
> >>>>>>>>> uclass_foreach_dev(dev, uc)
> >>>>>>>>> ret = scsi_scan_dev(dev, verbose);
> >>>>>>>>> ...
> >>>>>>>>> }
> >>>>>>>>> === ===
> >>>>>>>>>
> >>>>>>>>> Since scsn_scan() can be directly called by "scsi rescan" command,
> >>>>>>>>> There seems to be no generic hook, or event, available in order to
> >>>>>>>>> call efi_disk_create().
> >>>>>>>>>
> >>>>>>>>> Do I miss anything?
> >>>>>>>>
> >>>>>>>> Could the event handler that gets called from somewhere around
> >>>>>>>> blk_create_device() just put it into an efi internal "todo list" which
> >>>>>>>> we then process using an efi event?
> >>>>>>>>
> >>>>>>>> EFI events will only get triggered on the next entry to efi land, so by
> >>>>>>>> then we should be safe.
> >>>>>>>
> >>>>>>> I think I now understand your suggestion; we are going to invent
> >>>>>>> a specialized event-queuing mechanism so that we can take any actions
> >>>>>>> later at appropriate time (probably in efi_init_obj_list()?).
> >>>>>>
> >>>>>> Uh, not sure I follow. There would be 2 events. One from the u-boot block layer to the efi_loader disk layer.
> >>>>>
> >>>>> This is a to-be-invented "specialized event-queuing mechanism"
> >>>>> in my language :) as we cannot use efi_create/signal_event() before
> >>>>> initializing EFI environment.
> >>>>>
> >>>>> This event will be expected to be 'signal'ed at every creation/deletion
> >>>>> of UCLASS_BLK device. Right?
> >>>>
> >>>> Correct.
> >>>>
> >>>>>
> >>>>>> That event handler creates a new efi event (like a timer w/ timeout=0).
> >>>>>
> >>>>> But when is this event handler fired?
> >>>>> I think the only possible timing is at efi_init_obj_list().
> >>>>
> >>>> We already walk through the event list on any u-boot/efi world switch.
> >>>
> >>> ? Where is the code?
> >>
> >> Ah, I must have misremembered, sorry. I think that was one proposed
> >> patch a while ago, but we didn't put it in.
> >>
> >> But worst case we can just put additional efi_timer_check() calls at
> >> strategic places if needed.
> >
> > Do you expect this kind of mechanism be implemented in my short-term fix?
>
> To be completely honest, I don't think your fix is very critical right
> now, since it touches a case that's known broken today already.

So while the issue can be easily reproduced and my fix is quite
simple and straightforward (but with a bit inefficiency :),
you won't accept it in the current form.

Right? It's totally up to you.

Thanks,
-Takahiro Akashi

> I would prefer if we could concentrate on the real path forward, where
> everything becomes implicit and we no longer need to sync the two object
> trees.
>
>
> Alex