Re: Hang when booting guest kernels compiled with clang after SRSO mitigations

[Nathan Chancellor <nathan@kernel.org>]

On Sat, Aug 12, 2023 at 03:46:42PM +0200, Borislav Petkov wrote:
> Btw, this:
> 
> https://github.com/ClangBuiltLinux/linux/commit/150c42407f87463c27a2459e06845965291d9973
> 
> Is this fixing a current issue and so it needs to go to Linus now?
> 
> If so, I'll expedite it too.

Yes, that fixes an error at link time when building with LTO:

https://github.com/ClangBuiltLinux/linux/issues/1909

That is commit 973ab2d61f33 ("x86/retpoline,kprobes: Fix position of
thunk sections with CONFIG_LTO_CLANG") in x86/core, with the conflicts
against SRSO resolved and the fix that Andrew Cooper pointed out
squashed in, in case my comment in the commit message was not clear
enough :)

https://lore.kernel.org/lkml/20230803230323.1478869-1-andrew.cooper3@citrix.com/

With that change and the other ld.lld change you already picked up in
x86/bugs, our builds should go back to green, then we can decide what to
do about that runtime warning based on Peter's series and Nick's ability
to get back up and running (I have his patch applied locally somewhere
so I don't mind collecting tags and sending it next week).

Thanks again for helping us with this, I know it has been chaotic.

Cheers,
Nathan