linux-kernel - Re: [PATCH] efi/efivars: create efivars mount point when get variable services are available

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Date:   Mon, 24 Aug 2020 21:03:20 +0800
From:   joeyli <jlee@...e.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     "Lee, Chun-Yi" <joeyli.kernel@...il.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>
Subject: Re: [PATCH] efi/efivars: create efivars mount point when get
 variable services are available

Hi Ard,

On Thu, Aug 20, 2020 at 11:30:27AM +0200, Ard Biesheuvel wrote:
> On Wed, 19 Aug 2020 at 11:28, Lee, Chun-Yi <joeyli.kernel@...il.com> wrote:
> >
> > The efivars filesystem depends on GetVariable or GetNextVariable EFI
> > runtime services. So the /sys/firmware/efi/efivars does not need to be
> > created when GetVariable and GetNextVariable are not available.
> >
> > It is useful for userland to determine the availability of efivars
> > filesystem.
> >
> > Cc: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> > Cc: Ard Biesheuvel <ardb@...nel.org>
> > Signed-off-by: "Lee, Chun-Yi" <jlee@...e.com>
> 
> Hello Joey,
> 
> This is not the right check to perform here: the efivarfs code could
> be instantiated using a different efivars abstraction, so whether the
> RT services are implemented is not entirely relevant.
> 
> Please look at commit f88814cc2578c121e6edef686365036db72af0ed
> ("efi/efivars: Expose RT service availability via efivars
> abstraction") for an explanation of the underlying issue, and update
> your patch accordingly.
>

Thanks for youre review! I will look at f88814cc257 and change my
patch for v2.

Joey Lee
 
> 
> > ---
> >  drivers/firmware/efi/efi.c | 13 ++++++++-----
> >  1 file changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> > index fdd1db025dbf..929fbf4dfd5d 100644
> > --- a/drivers/firmware/efi/efi.c
> > +++ b/drivers/firmware/efi/efi.c
> > @@ -404,11 +404,14 @@ static int __init efisubsys_init(void)
> >         if (error)
> >                 goto err_remove_group;
> >
> > -       /* and the standard mountpoint for efivarfs */
> > -       error = sysfs_create_mount_point(efi_kobj, "efivars");
> > -       if (error) {
> > -               pr_err("efivars: Subsystem registration failed.\n");
> > -               goto err_remove_group;
> > +       if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE |
> > +                                     EFI_RT_SUPPORTED_GET_NEXT_VARIABLE_NAME)) {
> > +               /* and the standard mountpoint for efivarfs */
> > +               error = sysfs_create_mount_point(efi_kobj, "efivars");
> > +               if (error) {
> > +                       pr_err("efivars: Subsystem registration failed.\n");
> > +                       goto err_remove_group;
> > +               }
> >         }
> >
> >         if (efi_enabled(EFI_DBG) && efi_enabled(EFI_PRESERVE_BS_REGIONS))
> > --
> > 2.16.4
> >