On Tue, 01 Jun 2021 17:36:15 +1000
Michael Ellerman [off-list ref] wrote:
Roman Bolshakov [off-list ref] writes:
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On Sat, May 29, 2021 at 09:39:49AM +1000, Michael Ellerman wrote:
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Roman Bolshakov [off-list ref] writes:
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This reverts commit b0b3b2c78ec075cec4721986a95abbbac8c3da4f.
Otherwise, direct kernel boot with initramfs no longer works in QEMU.
It's broken in some bizarre way because a valid initramfs is not
recognized anymore:
Found initrd at 0xc000000001f70000:0xc000000003d61d64
rootfs image is not initramfs (XZ-compressed data is corrupt); looks like an initrd
The issue is observed on v5.13-rc3 if the kernel is built with
defconfig, GCC 7.5.0 and GNU ld 2.32.0.
Are you able to try a different compiler?
Hi Michael,
I've just tried GCC 9.3.1 and the result is the same.
The offending patch has assembly inlines, they typically go through
binutils/GAS and it might also be a case when older binutils doesn't
implement something properly (i've seen this on x86 and arm).
Jump labels use asm goto, which is a compiler feature, but you're right
that the binutils version could also be important.
What ld versions have you tried?
And are those the toolchains from kernel.org or somewhere else?
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I test booting qemu constantly, but I don't use GCC 7.5.
And what qemu version are you using?
QEMU 3.1.1, but I've also tried 6.0.50 (QEMU master, 62c0ac5041e913) and
it fails the same way.
OK.
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I assume your initramfs is compressed with XZ? How large is it
compressed?
Yes, XZ. initramfs size is 30 MB (around 100 MB cpio size).
It's interesting that the issue doesn't happen if I pass initramfs from
host (11MB), then the initramfs can be recognized. It might be related
to initramfs size then and bigger initramfs that used to work no longer
work with v5.13-rc3.
Are you using qemu's -initrd option to pass the initramfs, or are you
building the initramfs into the kernel?
Hi Michael,
I'm hitting the same issue while trying to boot a RHEL9 guest with
the distro's default kernel/initramfs and grub.
Interestingly this doesn't happen with older QEMU, e.g. 4.2.0 that
is shipped with RHEL8. I've bissected to this commit from the
QEMU 5.0 era :
commit 8897ea5a9fc0aafa5ed7eee1e0c49893b91a2d87
Author: David Gibson [off-list ref]
Date: Thu Nov 28 16:37:04 2019 +1100
spapr: Don't attempt to clamp RMA to VRMA constraint
This mostly changes how memory is presented in the FDT.
Before 8897ea5a9fc, for a VM with 1 gig of RAM, we had several nodes,
first one being the VRMA (limited to 256 megs).
memory@20000000 {
ibm,associativity = <0x04 0x00 0x00 0x00 0x00>;
reg = <0x00 0x20000000 0x00 0x20000000>;
device_type = "memory";
};
memory@10000000 {
ibm,associativity = <0x04 0x00 0x00 0x00 0x00>;
reg = <0x00 0x10000000 0x00 0x10000000>;
device_type = "memory";
};
memory@0 {
ibm,associativity = <0x04 0x00 0x00 0x00 0x00>;
reg = <0x00 0x00 0x00 0x10000000>;
device_type = "memory";
};
Now we have a single node for all RAM:
memory@0 {
ibm,associativity = <0x04 0x00 0x00 0x00 0x00>;
reg = <0x00 0x00 0x00 0x40000000>;
device_type = "memory";
};
If I set an arbitrary constraint again on the VRMA, I get the
multiple memory nodes back and, depending on the value, the
boot succeeds. In my 1 gig RHEL9 guest case, I need to set
a VRMA size <= 0x32000000.
Not sure how this can relate to the initramfs though. I just see
that grub doens't map it at the same place:
0x0000000003100000 when boot fails
0x000000000f000000 when boot succeeds
In case this rings a bell...
quoted hunk ↗ jump to hunk
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So, I've created a small initramfs using only static busybox (2.7M
uncompressed, 960K compressed with xz). No error is produced and it
boots fine.
If I add a dummy file (11M off /dev/urandom) to the small busybox
initramfs, it boots and the init is started but I'm seeing the error:
rootfs image is not initramfs (XZ-compressed data is corrupt); looks like an initrd
sha1sum of the file inside initramfs doesn't match sha1sum on the host.
guest # sha1sum dummy
407c347e671ddd00f69df12b3368048bad0ebf0c dummy
# QEMU: Terminated
host $ sha1sum dummy
ed8494b3eecab804960ceba2c497270eed0b0cd1 dummy
sha1sum is the same in the guest and on the host for 10M dummy file:
guest # sha1sum dummy
43855f7a772a28cce91da9eb8f86f53bc807631f dummy
# QEMU: Terminated
host $ sha1sum dummy
43855f7a772a28cce91da9eb8f86f53bc807631f dummy
That might explain why bigger initramfs (or initramfs with bigger files)
doesn't boot - because some files might appear corrupted inside the guest.
Here're the sources of the initrd along with 11M dummy file:
https://drive.yadro.com/s/W8HdbPnaKmPPwK4
I've compressed it with:
$ find . 2>/dev/null | cpio -ocR 0:0 | xz --check=crc32 > ../initrd-dummy.xz
Hope this helps,
I haven't been able to reproduce any corruption, with various initramfs
sizes.
Can you send us your kernel .config & qemu command line.
And can you try the patch below?
cheers
diff --git a/arch/powerpc/kernel/jump_label.c b/arch/powerpc/kernel/jump_label.c
index ce87dc5ea23c..3d9878124cde 100644
--- a/arch/powerpc/kernel/jump_label.c
+++ b/arch/powerpc/kernel/jump_label.c
@@ -13,6 +13,9 @@ void arch_jump_label_transform(struct jump_entry *entry,
{
struct ppc_inst *addr = (struct ppc_inst *)jump_entry_code(entry);
+ if (!is_kernel_text((unsigned long)addr) && !is_kernel_inittext((unsigned long)addr))
+ printk("%s: addr %px %pS is not kernel text?\n", __func__, addr, addr);
+
I've applied this too. It doesn't produce any output in the crashing case.
On the contrary I get tons of them when I run with the hacked VRMA size,
but they show up much later, after we've already freed the initrd memory.
Cheers,
--
Greg
if (type == JUMP_LABEL_JMP)
patch_branch(addr, jump_entry_target(entry), 0);
else