Andrey Drobyshev
2022-Dec-21 16:38 UTC
[Libguestfs] [V2V PATCH v2 0/2] inspect: prioritize BIOS boot partition in firmware detection
The first patch is merely a functional style refactoring. The 2nd patch
introduces actual change in the logic.
v1 + upstream discussion:
https://listman.redhat.com/archives/libguestfs/2022-December/030401.html
Andrey Drobyshev (2):
inspect: use List.fold_left to iterate over partitions
inspect: check presence of BIOS boot partition to handle BIOS+GPT
setup
convert/inspect_source.ml | 38 ++++++++++++++++++++++++++------------
1 file changed, 26 insertions(+), 12 deletions(-)
--
2.31.1
Andrey Drobyshev
2022-Dec-21 16:38 UTC
[Libguestfs] [V2V PATCH v2 1/2] inspect: use List.fold_left to iterate over partitions
This patch is merely a refactoring and does not introduce any changes in
behaviour. It's used as a prelude for the next patch which prioritizes
BIOS boot partition when searching for the right firmware.
Co-authored-by: Laszlo Ersek <lersek at redhat.com>
Signed-off-by: Andrey Drobyshev <andrey.drobyshev at virtuozzo.com>
---
convert/inspect_source.ml | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/convert/inspect_source.ml b/convert/inspect_source.ml
index 056d0bca..42a26f68 100644
--- a/convert/inspect_source.ml
+++ b/convert/inspect_source.ml
@@ -225,26 +225,30 @@ and list_applications g root = function
* Otherwise, [BIOS] is returned.
*)
and get_firmware_bootable_device g - let rec uefi_ESP_guid =
"C12A7328-F81F-11D2-BA4B-00A0C93EC93B"
- and is_uefi_ESP dev part - let partnum = g#part_to_partnum part in
- g#part_get_gpt_type dev partnum = uefi_ESP_guid
- and parttype_is_gpt dev + let parttype_is_gpt dev try
g#part_get_parttype dev = "gpt"
with G.Error msg as exn ->
(* If it's _not_ "unrecognised disk label" then re-raise
it. *)
if g#last_errno () <> G.Errno.errno_EINVAL then raise exn;
debug "%s (ignored)" msg;
false
- and is_uefi_bootable_part part + in
+ let accumulate_partition esp_parts part let dev = g#part_to_dev part in
- parttype_is_gpt dev && is_uefi_ESP dev part
+ if parttype_is_gpt dev then
+ let partnum = g#part_to_partnum part in
+ let part_type_guid = g#part_get_gpt_type dev partnum in
+ match part_type_guid with
+ (* EFI system partition *)
+ | "C12A7328-F81F-11D2-BA4B-00A0C93EC93B" -> part ::
esp_parts
+ | _ -> esp_parts
+ else esp_parts
in
- let partitions = Array.to_list (g#list_partitions ()) in
- let partitions = List.filter is_uefi_bootable_part partitions in
+ let esp_partitions + Array.fold_left accumulate_partition []
(g#list_partitions ()) in
- match partitions with
+ match esp_partitions with
| [] -> I_BIOS
| partitions -> I_UEFI partitions
--
2.31.1
Andrey Drobyshev
2022-Dec-21 16:38 UTC
[Libguestfs] [V2V PATCH v2 2/2] inspect: check presence of BIOS boot partition to handle BIOS+GPT setup
If the guest uses BIOS firmware but GPT partitioned disk, v2v inspection
might fail to correctly detect the firmware being used by the source mathine.
Namely, consider the following GPT partition table:
Number Start (sector) End (sector) Size Code Name
1 2048 4095 1024.0 KiB EF02
2 4096 528383 256.0 MiB EF00
3 528384 125827071 59.7 GiB 8300
4 125827072 134215679 4.0 GiB 8200
where partition 1 is a BIOS boot partition (code 0xEF02, GPT partition
entry with GUID 21686148-6449-6E6F-744E-656564454649), and partition 2
is a EFI System partition (code 0xEF00, GPT partition entry with GUID
C12A7328-F81F-11D2-BA4B-00A0C93EC93B). The former is commonly used to
store the bootloader in BIOS+GPT machines. The latter is used by UEFI
powered machines.
Normally an OS installer wouldn't put those two together: if the disk is
being partitioned in GPT, there's either BIOS boot partition (if BIOS
firmware is used) or EFI System partition (if UEFI firmware is used).
However, GRUB2 will deal with such "busted" layout just fine, so this
configuration may exist. If it is the case, v2v inspection will detect the
presence of an EFI system partition and mistakenly mark the system as UEFI.
So let's prioritize Bios boot partition over ESP. As discussed in [1],
this solution is not entirely bulletproof. It will work in case a GPT
disk was first used in an UEFI machine, and then put into a BIOS machine
with an ESP partition remaining on it. It won't work in the opposite case,
i.e. when a GPT disk is moved from BIOS machine to UEFI machine with
BIOS boot partition remaining on it. However, it's better to prioritize
something, and the latter case is less probable than the former.
[1] https://listman.redhat.com/archives/libguestfs/2022-December/030401.html
Co-authored-by: Laszlo Ersek <lersek at redhat.com>
Signed-off-by: Andrey Drobyshev <andrey.drobyshev at virtuozzo.com>
---
convert/inspect_source.ml | 28 +++++++++++++++++++---------
1 file changed, 19 insertions(+), 9 deletions(-)
diff --git a/convert/inspect_source.ml b/convert/inspect_source.ml
index 42a26f68..a0d9f148 100644
--- a/convert/inspect_source.ml
+++ b/convert/inspect_source.ml
@@ -219,6 +219,9 @@ and list_applications g root = function
(* See if this guest could use UEFI to boot. It should use GPT and
* it should have an EFI System Partition (ESP).
*
+ * If the guest has BIOS boot partition present, this is likely a BIOS+GPT
+ * setup, so [BIOS] is returned.
+ *
* If it has ESP(s), then [UEFI devs] is returned where [devs] is the
* list of at least one ESP.
*
@@ -233,24 +236,31 @@ and get_firmware_bootable_device g debug
"%s (ignored)" msg;
false
in
- let accumulate_partition esp_parts part + let accumulate_partition
(esp_parts, bboot) part let dev = g#part_to_dev part in
if parttype_is_gpt dev then
let partnum = g#part_to_partnum part in
let part_type_guid = g#part_get_gpt_type dev partnum in
match part_type_guid with
(* EFI system partition *)
- | "C12A7328-F81F-11D2-BA4B-00A0C93EC93B" -> part ::
esp_parts
- | _ -> esp_parts
- else esp_parts
+ | "C12A7328-F81F-11D2-BA4B-00A0C93EC93B" -> part ::
esp_parts, bboot
+ (* BIOS boot partition *)
+ | "21686148-6449-6E6F-744E-656564454649" -> esp_parts, true
+ | _ -> esp_parts, bboot
+ else esp_parts, bboot
in
- let esp_partitions - Array.fold_left accumulate_partition []
(g#list_partitions ()) in
+ let esp_partitions, bios_boot + Array.fold_left accumulate_partition ([],
false) (g#list_partitions ()) in
- match esp_partitions with
- | [] -> I_BIOS
- | partitions -> I_UEFI partitions
+ (* If there's a BIOS boot partition present (0xef02 type for gdisk,
+ * "bios_grub" flag for parted), then this is likely a BIOS+GPT
setup.
+ * In this case we prioritize BIOS boot partition and detect BIOS firmware,
+ * no matter how many ESPs we've found.
+ *)
+ match esp_partitions, bios_boot with
+ | _ :: _, false -> I_UEFI esp_partitions
+ | _ -> I_BIOS
(* If some inspection fields are "unknown", then that indicates a
* failure in inspection, and we shouldn't continue. For an example
--
2.31.1