On 2018-07-24 17:32:14 [+0200], Ard Biesheuvel wrote:
> Please refer to what has been queued up in tip:efi/core. Sai has
> implemented a work queue for EFI calls so they occur from a kernel
> thread, and the mixed mode locking has been fixed as well.
I see commit 83a0a2ea0b99 ("efi/x86: Prevent reentrant firmware calls in
mixed mode") which fixes the locking issue I mentioned. Will this make
its way to the current kernel?
Regarding the workqueue in commit 3eb420e70d87 ("efi: Use a work queue
to invoke EFI Runtime Services"). The efi_call_virt_pointer() function
uses local_save_flags() while invoking the EFI function. Why does commit
message say "Since UEFI runtime services are typically invoked with
interrupts enabled,"?
Anyway, I would still like to get rid of task_lock() in efi_switch_mm().
Any objections to that?
If efi_switch_mm() is only invoked from kernel-thread (the mixed-mode
caller does not) the then you could use use_mm() / unuse_mm() instead.
Then I would be fine with task_lock() (but it would have to be moved to
the preemptible section (after efi_sync_low_kernel_mappings()).
Sebastian
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