Hi All,
> > >> The main problem is that we have just merged Sai's code to use a
> > >> work queue for invoking EFI services, and killing kworker threads
> > >> is obviously not going to make EFI any new friends.
> > >>
> > >> So I guess we should probably rework that code to use a dedicated
> > >> kthread, and just freeze it when it performs an illegal memory
> > >> access, and signal the completion in a way that makes the calling
> > >> thread understand that a) the call failed and b) runtime services
> > >> are no longer
> > available.
> > >
> > > Yes, this makes sense to me.
> > > Initially I did use a dedicated kthread for efi but moved to work
> > > queues later so
> > that the synchronization is well handled. I am ok to rework on the
> > patches, could we ask Ingo to hold onto efi_workqueue patches?
> > >
> >
> > I am fine with keeping them. We will have a different approach in
> > v4.19 than in subsequent kernels, but the workqueue approach is still
> > better than nothing at all.
As discussed in previous mails, I have implemented the below:
If kernel detects an illegal access by firmware to any efi region other than
efi boot time code/data,
a. It freezes "efi_rts_wq" (efi runtime services work queue).
b. Signals the requested process that an error occurred.
c. Disables EFI Runtime Services forever.
d. Explicitly calls the scheduler to schedule another process.
But, I have couple of questions:
1. Since we don't use "efi_rts_wq" for efi_reset_system(), the above solution
doesn't work if efi_reset_system() is buggy. We cannot neglect it either because
that's the issue faced by Al Stone and hence I started the patch set. So, I am thinking
to use long jump technique *only* for efi_reset_system(). Would you be OK with that?
Or please propose a new solution.
2. Also, as suggested, I haven’t used a dedicated "efi_kthread", I got this working with
the existing "efi_rts_wq" setup. Please note that, the existing "efi_rts_wq", has only one
worker thread. Could you please brief me on why we should have a dedicated kthread
and not leverage "efi_rts_wq" (I am unclear on this).
Regards,
Sai
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