diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2018-07-24 21:28:55 +0200 |
|---|---|---|
| committer | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2018-09-26 12:14:57 +0200 |
| commit | 4eda11175fd9241908efb523b7f6e8a7c15afdb7 (patch) | |
| tree | 7b1fbff2adbc65fe47a3a9d0b5156ba9f5a7fe07 /arch/x86/platform/efi | |
| parent | 3425d934fc0312f62024163736a7afe4de20c10f (diff) | |
efi/x86: drop task_lock() from efi_switch_mm()
efi_switch_mm() is a wrapper around switch_mm() which saves current's
->active_mm, sets the requests mm as ->active_mm and invokes
switch_mm().
I don't think that task_lock() is required during that procedure. It
protects ->mm which isn't changed here.
It needs to be mentioned that during the whole procedure (switch to
EFI's mm and back) the preemption needs to be disabled. A context switch
at this point would reset the cr3 value based on current->mm. Also, this
function may not be invoked at the same time on a different CPU because
it would overwrite the efi_scratch.prev_mm information.
Remove task_lock() and also update the comment to reflect it.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Diffstat (limited to 'arch/x86/platform/efi')
| -rw-r--r-- | arch/x86/platform/efi/efi_64.c | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index ee5d08f25ce4..e8da7f492970 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -619,18 +619,16 @@ void __init efi_dump_pagetable(void) /* * Makes the calling thread switch to/from efi_mm context. Can be used - * for SetVirtualAddressMap() i.e. current->active_mm == init_mm as well - * as during efi runtime calls i.e current->active_mm == current_mm. - * We are not mm_dropping()/mm_grabbing() any mm, because we are not - * losing/creating any references. + * in a kernel thread and user context. Preemption needs to remain disabled + * while the EFI-mm is borrowed. mmgrab()/mmdrop() is not used because the mm + * can not change under us. + * It should be ensured that there are no concurent calls to this function. */ void efi_switch_mm(struct mm_struct *mm) { - task_lock(current); efi_scratch.prev_mm = current->active_mm; current->active_mm = mm; switch_mm(efi_scratch.prev_mm, mm, NULL); - task_unlock(current); } #ifdef CONFIG_EFI_MIXED |