[tip: x86/alternatives] x86/mm: Fix {,un}use_temporary_mm() IRQ state

[tip-bot2 for Peter Zijlstra]

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

Commit-ID:     aef1d0209ddf127a8069aca5fa3a062be4136b76
Gitweb:        https://git.kernel.org/tip/aef1d0209ddf127a8069aca5fa3a062be4136b76
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Fri, 18 Apr 2025 11:50:34 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Fri, 18 Apr 2025 14:36:18 +02:00

x86/mm: Fix {,un}use_temporary_mm() IRQ state

As the function switch_mm_irqs_off() implies, it ought to be called with
IRQs *off*. Commit 58f8ffa91766 ("x86/mm: Allow temporary MMs when IRQs
are on") caused this to not be the case for EFI.

Ensure IRQs are off where it matters.

Fixes: 58f8ffa91766 ("x86/mm: Allow temporary MMs when IRQs are on")
Reported-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Tested-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250418095034.GR38216@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
---
 arch/x86/mm/tlb.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 79c124f..39761c7 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -986,6 +986,7 @@ struct mm_struct *use_temporary_mm(struct mm_struct *temp_mm)
 	struct mm_struct *prev_mm;
 
 	lockdep_assert_preemption_disabled();
+	guard(irqsave)();
 
 	/*
 	 * Make sure not to be in TLB lazy mode, as otherwise we'll end up
@@ -1018,6 +1019,7 @@ struct mm_struct *use_temporary_mm(struct mm_struct *temp_mm)
 void unuse_temporary_mm(struct mm_struct *prev_mm)
 {
 	lockdep_assert_preemption_disabled();
+	guard(irqsave)();
 
 	/* Clear the cpumask, to indicate no TLB flushing is needed anywhere */
 	cpumask_clear_cpu(smp_processor_id(), mm_cpumask(this_cpu_read(cpu_tlbstate.loaded_mm)));