linux-kernel - Re: [PATCH V2 1/3] x86/efi: Call efi_delete_dummy_variable() during efi subsystem initialization

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Message-ID: <CAKv+Gu_ZYGwgORet4ruL8=GUy75LMAuLeYD987FA3UVYuw8GMg@mail.gmail.com>
Date:   Thu, 8 Mar 2018 07:43:23 +0000
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
Cc:     linux-efi@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Chun-Yi <jlee@...e.com>, Borislav Petkov <bp@...en8.de>,
        Tony Luck <tony.luck@...el.com>,
        Will Deacon <will.deacon@....com>,
        Dave Hansen <dave.hansen@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        Ravi Shankar <ravi.v.shankar@...el.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Peter Zijlstra <peter.zijlstra@...el.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH V2 1/3] x86/efi: Call efi_delete_dummy_variable() during
 efi subsystem initialization

Hello Sai,

On 5 March 2018 at 23:23, Sai Praneeth Prakhya
<sai.praneeth.prakhya@...el.com> wrote:
> From: Sai Praneeth <sai.praneeth.prakhya@...el.com>
>
> Invoking efi_runtime_services() through efi_workqueue means all accesses
> to efi_runtime_services() should be done after efi_rts_wq has been
> created. efi_delete_dummy_variable() calls set_variable(), hence
> efi_delete_dummy_variable() should be called after efi_rts_wq has been
> created.
>
> efi_delete_dummy_variable() is called from efi_enter_virtual_mode()
> which is early in the boot phase (efi_rts_wq isn't created yet), so call
> efi_delete_dummy_variable() later in the boot phase i.e. while
> initializing efi subsystem. In the next patch, this is the place where
> we create efi_rts_wq and all the efi_runtime_services() will be called
> using efi_rts_wq.
>
> Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
> Suggested-by: Andy Lutomirski <luto@...nel.org>
> Cc: Lee, Chun-Yi <jlee@...e.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Bhupesh Sharma <bhsharma@...hat.com>
> Cc: Ricardo Neri <ricardo.neri@...el.com>
> Cc: Ravi Shankar <ravi.v.shankar@...el.com>
> Cc: Matt Fleming <matt@...eblueprint.co.uk>
> Cc: Peter Zijlstra <peter.zijlstra@...el.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> Cc: Dan Williams <dan.j.williams@...el.com>
> ---
>  arch/x86/include/asm/efi.h  | 1 -
>  arch/x86/platform/efi/efi.c | 6 ------
>  drivers/firmware/efi/efi.c  | 6 ++++++
>  include/linux/efi.h         | 3 +++
>  4 files changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
> index a399c1ebf6f0..43009e3f821b 100644
> --- a/arch/x86/include/asm/efi.h
> +++ b/arch/x86/include/asm/efi.h
> @@ -143,7 +143,6 @@ extern void __init efi_runtime_update_mappings(void);
>  extern void __init efi_dump_pagetable(void);
>  extern void __init efi_apply_memmap_quirks(void);
>  extern int __init efi_reuse_config(u64 tables, int nr_tables);
> -extern void efi_delete_dummy_variable(void);
>
>  struct efi_setup_data {
>         u64 fw_vendor;
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 9061babfbc83..a3169d14583f 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -893,9 +893,6 @@ static void __init kexec_enter_virtual_mode(void)
>
>         if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
>                 runtime_code_page_mkexec();
> -
> -       /* clean DUMMY object */
> -       efi_delete_dummy_variable();
>  #endif
>  }
>
> @@ -1015,9 +1012,6 @@ static void __init __efi_enter_virtual_mode(void)
>          * necessary relocation fixups for the new virtual addresses.
>          */
>         efi_runtime_update_mappings();
> -
> -       /* clean DUMMY object */
> -       efi_delete_dummy_variable();
>  }
>
>  void __init efi_enter_virtual_mode(void)
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index cd42f66a7c85..838b8efe639c 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -328,6 +328,12 @@ static int __init efisubsys_init(void)
>         if (!efi_enabled(EFI_BOOT))
>                 return 0;
>
> +       /*
> +        * Clean DUMMY object calls EFI Runtime Service, set_variable(), so
> +        * it should be invoked only after efi_rts_workqueue is ready.
> +        */
> +       efi_delete_dummy_variable();
> +

Is there any way to keep this local to arch/x86?

>         /* We register the efi directory at /sys/firmware/efi */
>         efi_kobj = kobject_create_and_add("efi", firmware_kobj);
>         if (!efi_kobj) {
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index f5083aa72eae..c4efb3ef0dfa 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -992,6 +992,7 @@ extern efi_status_t efi_query_variable_store(u32 attributes,
>                                              unsigned long size,
>                                              bool nonblocking);
>  extern void efi_find_mirror(void);
> +extern void efi_delete_dummy_variable(void);
>  #else
>  static inline void efi_late_init(void) {}
>  static inline void efi_free_boot_services(void) {}
> @@ -1002,6 +1003,8 @@ static inline efi_status_t efi_query_variable_store(u32 attributes,
>  {
>         return EFI_SUCCESS;
>  }
> +
> +static inline void efi_delete_dummy_variable(void) {}
>  #endif
>  extern void __iomem *efi_lookup_mapped_addr(u64 phys_addr);
>
> --
> 2.7.4
>