On Sat, 8 Jan 2022 at 17:44, Andy Lutomirski <luto@xxxxxxxxxx> wrote:
>
> This should be considerably more robust. It's also necessary for optimized
> for_each_possible_lazymm_cpu() on x86 -- without this patch, EFI calls in
> lazy context would remove the lazy mm from mm_cpumask().
>
> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
> arch/x86/platform/efi/efi_64.c | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> index 7515e78ef898..b9a571904363 100644
> --- a/arch/x86/platform/efi/efi_64.c
> +++ b/arch/x86/platform/efi/efi_64.c
> @@ -54,7 +54,7 @@
> * 0xffff_ffff_0000_0000 and limit EFI VA mapping space to 64G.
> */
> static u64 efi_va = EFI_VA_START;
> -static struct mm_struct *efi_prev_mm;
> +static temp_mm_state_t efi_temp_mm_state;
>
> /*
> * We need our own copy of the higher levels of the page tables
> @@ -461,15 +461,12 @@ void __init efi_dump_pagetable(void)
> */
> void efi_enter_mm(void)
> {
> - efi_prev_mm = current->active_mm;
> - current->active_mm = &efi_mm;
> - switch_mm(efi_prev_mm, &efi_mm, NULL);
> + efi_temp_mm_state = use_temporary_mm(&efi_mm);
> }
>
> void efi_leave_mm(void)
> {
> - current->active_mm = efi_prev_mm;
> - switch_mm(&efi_mm, efi_prev_mm, NULL);
> + unuse_temporary_mm(efi_temp_mm_state);
> }
>
> static DEFINE_SPINLOCK(efi_runtime_lock);
> --
> 2.33.1
>
