Re: [PATCH v8] efi: new 'connectefi' command

["Renaud Métrich via Grub-devel" <grub-devel@gnu.org>]

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Hello,

I hope this time this will be ok, I reworked the code based on Daniel's 
comments, but didn't integrate all of them, in particular the "nitems" 
comment and removing the export for grub_efidisk_reenumerate_disks(), 
which seems mandatory to me. Regarding the comment on "s" variable 
instead of "j", I've kept "s" because it's more self-explanatory ("s" 
means "step" in the array of steps to perform).

I've verified the functionality again on QEMU/KVM systems booted on Grub 
directly and having multiple disks: initially no disk is listed (because 
EFI didn't connect anything), then after issuing "connectefi 
<all|pciroot|disk>", disks show up.

Renaud.

Le 9/2/25 à 1:56 PM, Renaud Métrich a écrit :
> When network booting is used, trying to chainload to the local disk
> (which is used in deployment tools such as Red Hat Satellite) may fail
> when searching for the boot loader, e.g. /EFI/redhat/shimx64.efi:
> the boot loader file is listed, but not readable, because UEFI DISK I/O
> and/or SCSI DISK I/O devices are not connected.
> Sometimes devices are connected but not the partition of the disk
> matching $prefix, causing partition to not be found by"chainloader".
>
> This issue was seen already on:
> - VMWare systems with efi.quickboot enabled (which is the default)
> - QEMU/KVM when network booting and not enabling any disk
> - Physical hardware such as Cisco and HPE systems
>
> Typical chainload configuration used:
> -------- 8< ---------------- 8< ---------------- 8< --------
> unset prefix
> search --file --set=prefix /EFI/redhat/shimx64.efi
> if [ -n "$prefix" ]; then
>    chainloader ($prefix)/EFI/redhat/shimx64.efi
> ...
> -------- 8< ---------------- 8< ---------------- 8< --------
>
> This patch introduces a new "connectefi pciroot|disk|all" command which
> recursively connects all EFI devices starting from a given controller
> type:
> - if 'pciroot' is specified, recursion is performed for all PCI root
>    handles
> - if 'disk' is specified, recursion is performed for all SCSI and DISK
>    I/O handles (recommended usage to avoid connecting unwanted handles
>    which may impact Grub performances)
> - if 'all' is specified, recursion is performed on all handles (not
>    recommended since it may heavily impact Grub performances)
>
> Typical grub.cfg snippet would then be:
> -------- 8< ---------------- 8< ---------------- 8< --------
> connectefi disk
> unset prefix
> search --file --set=prefix /EFI/redhat/shimx64.efi
> if [ -n "$prefix" ]; then
>    chainloader ($prefix)/EFI/redhat/shimx64.efi
> ...
> -------- 8< ---------------- 8< ---------------- 8< --------
>
> The code is easily extensible to handle other arguments in the future if
> needed.
>
> Signed-off-by: Renaud Métrich <rmetrich@redhat.com>
> ---
>   docs/grub.texi                      |  33 ++++
>   grub-core/Makefile.core.def         |   6 +
>   grub-core/commands/efi/connectefi.c | 233 ++++++++++++++++++++++++++++
>   grub-core/disk/efi/efidisk.c        |  13 ++
>   include/grub/efi/disk.h             |   2 +
>   5 files changed, 287 insertions(+)
>   create mode 100644 grub-core/commands/efi/connectefi.c
>
> diff --git a/docs/grub.texi b/docs/grub.texi
> index 34b3484dc..3b8b05fca 100644
> --- a/docs/grub.texi
> +++ b/docs/grub.texi
> @@ -3918,6 +3918,7 @@ Modules can be loaded via the @command{insmod} (@pxref{insmod}) command.
>   * cmp_module::
>   * cmp_test_module::
>   * configfile_module::
> +* connectefi_module::
>   * cpio_module::
>   * cpio_be_module::
>   * cpuid_module::
> @@ -4413,6 +4414,14 @@ This module provides support for the commands: @command{configfile},
>   @command{extract_entries_configfile}, @command{.} (dot command).
>   @xref{configfile} / @pxref{source}.
>   
> +@node connectefi_module
> +@section connectefi
> +This module provides support for the @command{connectefi} command. This command
> +can be used on EFI platforms to connect SCSI I/O and DISK I/O EFI handles,
> +which may be required when chainloading to the disk after booting from the
> +network, or from one disk to another for example.
> +@pxref{chainloader} / @pxref{connectefi} for more information.
> +
>   @node cpio_module
>   @section cpio
>   This module provides support for the CPIO archive file format. This module is
> @@ -6147,6 +6156,11 @@ image.
>   If you specify the option @option{--force}, then load @var{file} forcibly,
>   whether it has a correct signature or not. This is required when you want to
>   load a defective boot loader, such as SCO UnixWare 7.1.
> +
> +On EFI platforms, when initially network booting, or booting from another disk,
> +it may be required to connect the EFI devices using @command{connectefi}
> +command (@pxref{connectefi}) prior to chainloading to the disk, otherwise no
> +disk may show up or the EFI partition on the disk may not be readable.
>   @end deffn
>   
>   
> @@ -6715,6 +6729,25 @@ after @command{configfile} returns.
>   @end deffn
>   
>   
> +@node connectefi
> +@subsection connectefi
> +
> +@deffn Command connectefi pciroot|disk|all
> +When used with @samp{pciroot} parameter, all PCI devices are recursively
> +connected, which may be a slow operation, depending on the hardware.
> +
> +When used with @samp{disk} parameter, only SCSI I/O and DISK I/O devices are
> +connected; this is the recommended usage when chainloading to internal disk,
> +unless some disks are not detected anyway, in such case @samp{all} may be used
> +and a bug be reported to enhance the implementation.
> +
> +When used with @samp{all} parameter, all EFI devices are recursively connected,
> +which may be an extremely slow operation, depending on the hardware.
> +
> +Note: This command is only available on EFI platforms.
> +@end deffn
> +
> +
>   @node cpuid
>   @subsection cpuid
>   
> diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
> index b3f71196a..b68ac267a 100644
> --- a/grub-core/Makefile.core.def
> +++ b/grub-core/Makefile.core.def
> @@ -840,6 +840,12 @@ module = {
>     enable = efi;
>   };
>   
> +module = {
> +  name = connectefi;
> +  efi = commands/efi/connectefi.c;
> +  enable = efi;
> +};
> +
>   module = {
>     name = blocklist;
>     common = commands/blocklist.c;
> diff --git a/grub-core/commands/efi/connectefi.c b/grub-core/commands/efi/connectefi.c
> new file mode 100644
> index 000000000..3c1d628ef
> --- /dev/null
> +++ b/grub-core/commands/efi/connectefi.c
> @@ -0,0 +1,233 @@
> +/*
> + *  GRUB  --  GRand Unified Bootloader
> + *  Copyright (C) 2025  Free Software Foundation, Inc.
> + *
> + *  GRUB is free software: you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation, either version 3 of the License, or
> + *  (at your option) any later version.
> + *
> + *  GRUB is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + *  You should have received a copy of the GNU General Public License
> + *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <grub/types.h>
> +#include <grub/mm.h>
> +#include <grub/misc.h>
> +#include <grub/efi/api.h>
> +#include <grub/efi/pci.h>
> +#include <grub/efi/efi.h>
> +#include <grub/efi/disk.h>
> +#include <grub/command.h>
> +#include <grub/err.h>
> +#include <grub/i18n.h>
> +
> +GRUB_MOD_LICENSE ("GPLv3+");
> +
> +struct grub_efi_handle_list
> +{
> +  struct grub_efi_handle_list *next;
> +  struct grub_efi_handle_list **prev;
> +  grub_efi_handle_t handle;
> +};
> +typedef struct grub_efi_handle_list grub_efi_handle_list_t;
> +
> +enum search_item_flag
> +{
> +  SEARCH_NONE = 0,
> +  SEARCH_LOOP = 1,
> +  SEARCH_RECURSIVE = 2
> +};
> +typedef enum search_item_flag search_item_flag_t;
> +
> +struct search_item
> +{
> +  grub_guid_t guid;
> +  const char *name;
> +  search_item_flag_t flags;
> +};
> +typedef struct search_item search_item_t;
> +
> +static grub_efi_status_t
> +grub_efi_connect_controller (grub_efi_handle_t controller_handle,
> +			     grub_efi_handle_t *driver_image_handle,
> +			     grub_efi_device_path_protocol_t *remaining_device_path,
> +			     grub_efi_boolean_t recursive)
> +{
> +  return grub_efi_system_table->boot_services->connect_controller (
> +		    controller_handle, driver_image_handle,
> +		    remaining_device_path, recursive);
> +}
> +
> +static bool
> +is_in_list (grub_efi_handle_t handle, grub_efi_handle_list_t *handles)
> +{
> +  grub_efi_handle_list_t *e;
> +
> +  FOR_LIST_ELEMENTS (e, handles)
> +    if (e->handle == handle)
> +      return true;
> +
> +  return false;
> +}
> +
> +static void
> +free_handle_list (grub_efi_handle_list_t **handles_p)
> +{
> +  grub_efi_handle_list_t *e, *n;
> +
> +  FOR_LIST_ELEMENTS_SAFE(e, n, *handles_p)
> +    grub_free (e);
> +
> +  *handles_p = NULL;
> +}
> +
> +static grub_err_t
> +grub_cmd_connectefi (grub_command_t cmd __attribute__ ((unused)),
> +		     int argc, char **args)
> +{
> +  int s;
> +  search_item_t pciroot_items[] =
> +    {
> +      { GRUB_EFI_PCI_ROOT_IO_GUID, "PCI root", SEARCH_RECURSIVE }
> +    };
> +  search_item_t disk_items[] =
> +    {
> +      { GRUB_EFI_PCI_ROOT_IO_GUID, "PCI root", SEARCH_NONE },
> +      { GRUB_EFI_PCI_IO_GUID, "PCI", SEARCH_LOOP },
> +      { GRUB_EFI_SCSI_IO_PROTOCOL_GUID, "SCSI I/O", SEARCH_RECURSIVE },
> +      { GRUB_EFI_DISK_IO_GUID, "DISK I/O", SEARCH_RECURSIVE }
> +    };
> +  search_item_t *items = NULL;
> +  int nitems = 0;
> +  grub_err_t grub_err = GRUB_ERR_NONE;
> +  bool connected_devices = false;
> +  grub_efi_handle_list_t *already_handled = NULL;
> +  grub_efi_handle_t *handles = NULL;
> +
> +  if (argc != 1)
> +    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument expected"));
> +
> +  if (grub_strcmp (args[0], "pciroot") == 0)
> +    {
> +      items = pciroot_items;
> +      nitems = ARRAY_SIZE (pciroot_items);
> +    }
> +  else if (grub_strcmp (args[0], "disk") == 0)
> +    {
> +      items = disk_items;
> +      nitems = ARRAY_SIZE (disk_items);
> +    }
> +  else if (grub_strcmp (args[0], "all") == 0)
> +    {
> +      items = NULL;
> +      nitems = 1;
> +    }
> +  else
> +    return grub_error (GRUB_ERR_BAD_ARGUMENT,
> +		       N_("unexpected argument: `%s'"), args[0]);
> +
> +  for (s = 0; s < nitems; s++)
> +    {
> +      grub_efi_uintn_t num_handles, i;
> +      int loop = 0;
> +      bool connected = false;
> +
> + loop:
> +      loop++;
> +      if (items != NULL)
> +	{
> +	  grub_dprintf ("efi", "step '%s' loop %d:\n", items[s].name, loop);
> +	  handles = grub_efi_locate_handle (GRUB_EFI_BY_PROTOCOL,
> +					    &items[s].guid, 0, &num_handles);
> +	}
> +      else
> +	handles = grub_efi_locate_handle (GRUB_EFI_ALL_HANDLES,
> +					  NULL, NULL, &num_handles);
> +
> +      if (handles == NULL)
> +	continue;
> +
> +      for (i = 0; i < num_handles; i++)
> +	{
> +	  grub_efi_handle_t handle = handles[i];
> +	  grub_efi_status_t status;
> +	  grub_efi_handle_list_t *item;
> +
> +	  /* Skip already handled handles */
> +	  if (is_in_list (handle, already_handled))
> +	    {
> +	      grub_dprintf ("efi", "  handle %p: already processed\n", handle);
> +	      continue;
> +	    }
> +
> +	  status = grub_efi_connect_controller (handle, NULL, NULL,
> +						!items || items[s].flags & SEARCH_RECURSIVE ? 1 : 0);
> +	  if (status == GRUB_EFI_SUCCESS)
> +	    {
> +	      connected = true;
> +	      connected_devices = true;
> +	      grub_dprintf ("efi", "  handle %p: connected\n", handle);
> +	    }
> +	  else
> +	    grub_dprintf ("efi", "  handle %p: failed to connect (%"
> +			  PRIuGRUB_EFI_UINTN_T ")\n", handle, status);
> +
> +	  item = grub_malloc (sizeof (*item));
> +	  if (item == NULL)
> +	    goto fail; /* fatal */
> +	  grub_list_push (GRUB_AS_LIST_P (&already_handled), GRUB_AS_LIST (item));
> +	  item->handle = handle;
> +	}
> +
> +      grub_free (handles);
> +      handles = NULL;
> +
> +      /*
> +       * If devices got connected, new devices may be visible now, so loop to
> +       * connect those
> +       */
> +      if (items != NULL && (items[s].flags & SEARCH_LOOP) && connected == true)
> +	{
> +	  connected = false;
> +	  goto loop;
> +	}
> +
> +      /* Otherwise we are done with this step, proceed to next step */
> +      free_handle_list (&already_handled);
> +    }
> +
> +fail:
> +  grub_free (handles);
> +  free_handle_list (&already_handled);
> +
> +  if (connected_devices)
> +    grub_efidisk_reenumerate_disks ();
> +
> +  return grub_err;
> +}
> +
> +static grub_command_t cmd;
> +
> +GRUB_MOD_INIT(connectefi)
> +{
> +  cmd = grub_register_command ("connectefi", grub_cmd_connectefi,
> +			       "pciroot|disk|all",
> +			       N_("Connect EFI handles."
> +				  " If 'pciroot' is specified, connect PCI"
> +				  " root EFI handles recursively."
> +				  " If 'disk' is specified, connect SCSI"
> +				  " and DISK I/O EFI handles recursively."
> +				  " If 'all' is specified, connect all"
> +				  " EFI handles recursively."));
> +}
> +
> +GRUB_MOD_FINI(connectefi)
> +{
> +  grub_unregister_command (cmd);
> +}
> diff --git a/grub-core/disk/efi/efidisk.c b/grub-core/disk/efi/efidisk.c
> index 3b5ed5691..4cba5b43a 100644
> --- a/grub-core/disk/efi/efidisk.c
> +++ b/grub-core/disk/efi/efidisk.c
> @@ -396,6 +396,19 @@ enumerate_disks (void)
>     free_devices (devices);
>   }
>   
> +void
> +grub_efidisk_reenumerate_disks (void)
> +{
> +  free_devices (fd_devices);
> +  free_devices (hd_devices);
> +  free_devices (cd_devices);
> +  fd_devices = NULL;
> +  hd_devices = NULL;
> +  cd_devices = NULL;
> +
> +  enumerate_disks ();
> +}
> +
>   static int
>   grub_efidisk_iterate (grub_disk_dev_iterate_hook_t hook, void *hook_data,
>   		      grub_disk_pull_t pull)
> diff --git a/include/grub/efi/disk.h b/include/grub/efi/disk.h
> index 254475c84..6845c2f1f 100644
> --- a/include/grub/efi/disk.h
> +++ b/include/grub/efi/disk.h
> @@ -27,6 +27,8 @@ grub_efi_handle_t
>   EXPORT_FUNC(grub_efidisk_get_device_handle) (grub_disk_t disk);
>   char *EXPORT_FUNC(grub_efidisk_get_device_name) (grub_efi_handle_t *handle);
>   
> +void EXPORT_FUNC(grub_efidisk_reenumerate_disks) (void);
> +
>   void grub_efidisk_init (void);
>   void grub_efidisk_fini (void);
>   

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