Re: [PATCH v8 3/4] Boot var automatic management for removable medias

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

On Wed, Jun 07, 2023 at 10:00:37AM +0300, Ilias Apalodimas wrote:
> On Wed, 7 Jun 2023 at 09:52, AKASHI Takahiro <takahiro.akashi@linaro.org> wrote:
> >
> > On Wed, Jun 07, 2023 at 09:38:30AM +0300, Ilias Apalodimas wrote:
> > > On Wed, 7 Jun 2023 at 03:41, AKASHI Takahiro <takahiro.akashi@linaro.org> wrote:
> > > >
> > > > On Tue, Jun 06, 2023 at 09:37:20AM -0700, Raymond Mao wrote:
> > > > > Changes for complying to EFI spec §3.5.1.1
> > > > > 'Removable Media Boot Behavior'.
> > > > > Boot variables can be automatically generated during a removable
> > > > > media is probed. At the same time, unused boot variables will be
> > > > > detected and removed.
> > > > > Please note that currently the function 'efi_disk_remove' is being
> > > > > invoked during exiting U-Boot and booting an OS - that is why we
> > > > > don't add the boot variables management inside 'efi_disk_remove'.
> > > >
> > > > It's not accurate.
> > > > For instance, a user may run "scsi scan" or "usb reset" to re-enumerate
> > > > devices added (or removed). They will invoke "remove" against pre-existing
> > > > devices before invoking a "probe" routine.
> > > >
> > > > So the text above doesn't justify not implementing "remove" hook.
> > >
> > > I am not sure I am following you here.  Yes resetting the device will
> > > call the remove callback and it's a current problem of the existing
> > > implementation,
> >
> > I think it is a design decision.
> 
> It's not.  Ideally, we should call the _remove() callbacks and
> reconfigure the boot options correctly if a device gets unplugged or
> the subsystem is restarted. However, at least in my opinion, the
> problem isn't that big at the moment to prevent the patches from
> getting merged.
> If you restart the subsystem the same boot options will be rescanned
> and the device will be able to boot.  The corner case here is scanning
> a few boot options and then *removing* the device.  But in that case,
> the device wasn't going to boot anyway from the removed media.

First of all, we should distinguish two cases when you mention
the *existing* issues in Raymond's current implementation:
1. Some device is added or removed when we are still on U-Boot
2. When we are existing U-Boot

In the above text, you mention case(1) which is not covered by
his original commit message. It is one reason why I think that the commit
message is not accurate.

> >
> > > but why is the commit message inaccurate?  Won't
> > > exiting u-boot to jump to the OS call all the _remove() functions?
> >
> > Exiting U-Boot is irrelevant to maintaining boot options.
> 
> In theory yes,  but the reality is that you can't remove the boot
> options and rewrite flashes of embedded boards, with a limited
> lifetime, every time you boot your OS.  So adding it on the _remove

Here you have much more explanation than the original message
has for case(2). It is another reason why the commit message is
not accurate (or I should say 'not enough'). Without those texts,
most people won't understand what the commit message tries to say.

-Takahiro Akashi

> We could in the future add an extra flag to the
> callback *now* is a bad idea and that's what the commit message is
> trying to hint.
> remove callback which only gets set to false when we are exiting
> u-boot

> Thanks
> /Ilias
> >
> > -Takahiro Akashi
> >
> > > Thanks
> > > /Ilias
> > > >
> > > > -Takahiro Akashi
> > > >
> > > > > Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
> > > > > Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
> > > > > Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> > > > > ---
> > > > > Changes in v3
> > > > > - Split the patch into moving and renaming functions and
> > > > >   individual patches for each changed functionality
> > > > > Changes in v5
> > > > > - Move function call of efi_bootmgr_update_media_device_boot_option()
> > > > >   from efi_init_variables() to efi_init_obj_list()
> > > > > Changes in v6
> > > > > - Revert unrelated changes
> > > > > Changes in v7
> > > > > - adapt the return code of function
> > > > >   efi_bootmgr_update_media_device_boot_option()
> > > > > Changes in v8
> > > > > - add a note in the commit message for future reference
> > > > >
> > > > >  lib/efi_loader/efi_disk.c  | 7 +++++++
> > > > >  lib/efi_loader/efi_setup.c | 5 +++++
> > > > >  2 files changed, 12 insertions(+)
> > > > >
> > > > > diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c
> > > > > index d2256713a8..d9b48ecf64 100644
> > > > > --- a/lib/efi_loader/efi_disk.c
> > > > > +++ b/lib/efi_loader/efi_disk.c
> > > > > @@ -687,6 +687,13 @@ int efi_disk_probe(void *ctx, struct event *event)
> > > > >                       return -1;
> > > > >       }
> > > > >
> > > > > +     /* only do the boot option management when UEFI sub-system is initialized */
> > > > > +     if (efi_obj_list_initialized == EFI_SUCCESS) {
> > > > > +             ret = efi_bootmgr_update_media_device_boot_option();
> > > > > +             if (ret != EFI_SUCCESS)
> > > > > +                     return -1;
> > > > > +     }
> > > > > +
> > > > >       return 0;
> > > > >  }
> > > > >
> > > > > diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
> > > > > index 58d4e13402..877f3878d6 100644
> > > > > --- a/lib/efi_loader/efi_setup.c
> > > > > +++ b/lib/efi_loader/efi_setup.c
> > > > > @@ -245,6 +245,11 @@ efi_status_t efi_init_obj_list(void)
> > > > >       if (ret != EFI_SUCCESS)
> > > > >               goto out;
> > > > >
> > > > > +     /* update boot option after variable service initialized */
> > > > > +     ret = efi_bootmgr_update_media_device_boot_option();
> > > > > +     if (ret != EFI_SUCCESS)
> > > > > +             goto out;
> > > > > +
> > > > >       /* Define supported languages */
> > > > >       ret = efi_init_platform_lang();
> > > > >       if (ret != EFI_SUCCESS)
> > > > > --
> > > > > 2.25.1
> > > > >