Adding the xen-devel list as requested in grub-devel [0]:
On Thu, Aug 11, 2022 at 1:51 PM Daniel Kiper <dkiper@xxxxxxxxxxxx> wrote:
In general patches LGTM. However, I would prefer to hear an opinion from Xen
folks too. So, please repost the patch set and add
xen-devel@xxxxxxxxxxxxxxxxxxxx
to the list of recipients.
[0] https://lists.gnu.org/archive/html/grub-devel/2022-08/msg00115.html
Thanks,
Mauricio
...
The linux_xen template seems to be broken for multiple initrd files.
Linux fails to boot when it needs a real initrd but early/microcode
initrd(s) are found by grub-mkconfig.
Patch 1 allows initrd(s) other than the first early/microcode initrd
to be loaded at all, fixing an implementation error for multiboot[2].
Patch 2 allows Linux to get the real initrd as initrd (vs. an early/
microcode-only initrd), thus being able to boot if it needs a initrd.
Synthetic tests:
---
# touch /boot/xen /boot/microcode.cpio
Original:
# grub-mkconfig 2>/dev/null | grep -P '^\t(multiboot|module)'
multiboot /boot/xen ...
module /boot/vmlinuz-5.4.0-122-generic ...
module --nounzip /boot/microcode.cpio
/boot/initrd.img-5.4.0-122-generic
Patch 1:
# grub-mkconfig 2>/dev/null | grep -P '^\t(multiboot|module)'
multiboot /boot/xen ...
module /boot/vmlinuz-5.4.0-122-generic ...
module --nounzip /boot/microcode.cpio
module --nounzip /boot/initrd.img-5.4.0-122-generic
Patch 2:
# grub-mkconfig 2>/dev/null | grep -P '^\t(multiboot|module)'
multiboot /boot/xen ...
module /boot/vmlinuz-5.4.0-122-generic ...
module --nounzip /boot/initrd.img-5.4.0-122-generic
module --nounzip /boot/microcode.cpio
With fake multiboot2 header:
# echo -en '\xd6\x50\x52\xe8\x00\x00\x00\x00' > /boot/xen
# echo -en '\x00\x00\x00\x00\x2a\xaf\xad\x17' >> /boot/xen
# echo -en '\x00\x00\x00\x00\x00\x00\x00\x00' >> /boot/xen
# echo -en '\x00\x00\x00\x00\x00\x00\x00\x00' >> /boot/xen
# grub-file --is-x86-multiboot2 /boot/xen; echo $?
0
# grub-mkconfig 2>/dev/null | grep -P '^\t(multiboot|module)'
multiboot2 /boot/xen ...
module2 /boot/vmlinuz-5.4.0-122-generic ...
module2 --nounzip /boot/initrd.img-5.4.0-122-generic
module2 --nounzip /boot/microcode.cpio
Regular tests:
---
Debug patch:
__start_xen() @ xen.git:xen/arch/x86/setup.c
...
+for (i = 0; i < mbi->mods_count; i++)
+ printk("MODULE %d size %d string %s\n",
+ i, mod[i].mod_end - mod[i].mod_start,
(char*)__va(mod[i].string));
+
bitmap_fill(module_map, mbi->mods_count);
__clear_bit(0, module_map); /* Dom0 kernel is always first */
For /boot/microcode.cpio:
$ sudo apt install microcode-initrd # on Ubuntu
$ du --bytes /boot/...
13660416 /boot/vmlinuz-5.4.0-122-generic
33062542 /boot/initrd.img-5.4.0-122-generic
5045248 /boot/microcode.cpio
Original:
(XEN) MODULE 0 size 13660416 string placeholder
root=UUID=74dd579c-a377-487d-b8f7-bc7c6df13ba1 ro console=ttyS0
(XEN) MODULE 1 size 5045248 string /boot/initrd.img-5.4.0-122-generic
...
[ 2.505207] Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(0,0)
Patch 1:
(XEN) MODULE 0 size 13660416 string placeholder
root=UUID=74dd579c-a377-487d-b8f7-bc7c6df13ba1 ro console=ttyS0
(XEN) MODULE 1 size 5045248 string
(XEN) MODULE 2 size 33062542 string
...
[ 1.890498] Freeing initrd memory: 4928K
...
[ 2.710948] Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(0,0)
Patch 2:
(XEN) MODULE 0 size 13660416 string placeholder
root=UUID=74dd579c-a377-487d-b8f7-bc7c6df13ba1 ro console=ttyS0
(XEN) MODULE 1 size 33062542 string
(XEN) MODULE 2 size 5045248 string
...
[ 1.968578] Freeing initrd memory: 32288K
...
[ 2.844889] Run /init as init process
[ 2.916532] systemd-udevd[148]: Starting version 245.4-4ubuntu3.17
Xen code:
---
Key code path for this patchset:
@ xen.git:xen/arch/x86/setup.c:
void __init noreturn __start_xen(unsigned long mbi_p)
{
...
unsigned int initrdidx, ...
multiboot_info_t *mbi;
module_t *mod;
unsigned long ..., module_map[1];
...
mbi = __va(mbi_p);
...
mod = __va(mbi->mods_addr);
...
bitmap_fill(module_map, mbi->mods_count);
__clear_bit(0, module_map); /* Dom0 kernel is always first */
...
microcode_grab_module(module_map, mbi);
# ucode=number can __test_and_clear_bit(number, module_map),
# ucode=scan can't.
...
initrdidx = find_first_bit(module_map, mbi->mods_count);
if ( bitmap_weight(module_map, mbi->mods_count) > 1 )
printk(XENLOG_WARNING
"Multiple initrd candidates, picking module #%u\n",
initrdidx);
...
/*
* ... The second module, if present, is an initrd ramdisk.
*/
dom0 = create_dom0(mod, modules_headroom,
initrdidx < mbi->mods_count ? mod + initrdidx :
NULL,
kextra, loader);
...
Mauricio Faria de Oliveira (2):
templates/linux_xen: Properly load multiple initrd files
templates/linux_xen: Properly order the multiple initrd files
util/grub.d/20_linux_xen.in | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
