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SubjectRe: 4.14.9 with CONFIG_MCORE2 fails to boot
On 12/29/2017 10:46 AM, Alexander Tsoy wrote:
> В Пт, 29/12/2017 в 09:32 -0800, Dave Hansen пишет:
>> Does anyone have the results of build that they can share?  (vmlinux,
>> vmlinuz/bzImage,, .config).  That, plus a corresponding
>> serial log with an oops would be helpful.
> Here you are:

Alexander, thanks a bunch for the quick turnaround on this. It is much

With your binary, I can reproduce this in a KVM guest. Seems we manage
to get to paranoid_entry with a kernel GS value, but the user page
tables in place. We don't smash the #DF stack because we reset the
stack at each new #DF. I think the loop that we get stuck in goes
something like this:

1. Hardware does #DF, calls double_fault
2. call paranoid_entry
3. check MSR for GSBASE, see it has kernel value, skip SWAPGS and
switch to kernel page tables
4. touch stack, try to #PF, but can't touch stack, so #DF and goto 1

The real question is where we double-faulted from in the first place
with a kernel GSBASE and user CR3. I think I just need to disable KASLR
and do a little work in gdb to look at the stack on the first
double-fault, but we'll see.

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