[tip: x86/alternatives] x86/efi: Make efi_enter/leave_mm() use the use_/unuse_temporary_mm() machinery

[tip-bot2 for Andy Lutomirski]

The following commit has been merged into the x86/alternatives branch of tip:

Commit-ID:     e7021e2fe0b4335523d3f6e2221000bdfc633b62
Gitweb:        https://git.kernel.org/tip/e7021e2fe0b4335523d3f6e2221000bdfc633b62
Author:        Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate:    Wed, 02 Apr 2025 11:45:39 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Sat, 12 Apr 2025 10:06:04 +02:00

x86/efi: Make efi_enter/leave_mm() use the use_/unuse_temporary_mm() machinery

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().

[ mingo: Merged it on top of x86/alternatives ]

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250402094540.3586683-7-mingo@xxxxxxxxxx
---
 arch/x86/platform/efi/efi_64.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index ac57259..a5d3496 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -434,15 +434,12 @@ void __init efi_dump_pagetable(void)
  */
 static 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_prev_mm = use_temporary_mm(&efi_mm);
 }
 
 static void efi_leave_mm(void)
 {
-	current->active_mm = efi_prev_mm;
-	switch_mm(&efi_mm, efi_prev_mm, NULL);
+	unuse_temporary_mm(efi_prev_mm);
 }
 
 void arch_efi_call_virt_setup(void)