diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2025-04-30 11:11:54 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-05-06 12:28:57 +0300 |
| commit | 7f9958230d8a79d474829bee25ec9426397335ce (patch) | |
| tree | 93bad6046e7f47fe93c3bad0d4c1da06927bfbda /arch/x86/mm | |
| parent | 43c2df7e2b08db6d65ce9707e4090f1f0c61f2f6 (diff) | |
| download | linux-7f9958230d8a79d474829bee25ec9426397335ce.tar.xz | |
x86/mm: Fix false positive warning in switch_mm_irqs_off()
Multiple testers reported the following new warning:
WARNING: CPU: 0 PID: 0 at arch/x86/mm/tlb.c:795
Which corresponds to:
if (IS_ENABLED(CONFIG_DEBUG_VM) && WARN_ON_ONCE(prev != &init_mm &&
!cpumask_test_cpu(cpu, mm_cpumask(next))))
cpumask_set_cpu(cpu, mm_cpumask(next));
So the problem is that unuse_temporary_mm() explicitly clears
that bit; and it has to, because otherwise the flush_tlb_mm_range() in
__text_poke() will try sending IPIs, which are not at all needed.
See also:
https://lore.kernel.org/all/20241113095550.GBZzR3pg-RhJKPDazS@fat_crate.local/
Notably, the whole {,un}use_temporary_mm() thing requires preemption to
be disabled across it with the express purpose of keeping all TLB
nonsense CPU local, such that invalidations can also stay local etc.
However, as a side-effect, we violate this above WARN(), which sorta
makes sense for the normal case, but very much doesn't make sense here.
Change unuse_temporary_mm() to mark the mm_struct such that a further
exception (beyond init_mm) can be grafted, to keep the warning for all
the other cases.
Reported-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Reported-by: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rik van Riel <riel@surriel.com>
Link: https://lore.kernel.org/r/20250430081154.GH4439@noisy.programming.kicks-ass.net
Diffstat (limited to 'arch/x86/mm')
| -rw-r--r-- | arch/x86/mm/init.c | 3 | ||||
| -rw-r--r-- | arch/x86/mm/tlb.c | 3 |
2 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index f8c74d19bebb..aa56d9ac0b8f 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -28,6 +28,7 @@ #include <asm/text-patching.h> #include <asm/memtype.h> #include <asm/paravirt.h> +#include <asm/mmu_context.h> /* * We need to define the tracepoints somewhere, and tlb.c @@ -830,6 +831,8 @@ void __init poking_init(void) /* Xen PV guests need the PGD to be pinned. */ paravirt_enter_mmap(text_poke_mm); + set_notrack_mm(text_poke_mm); + /* * Randomize the poking address, but make sure that the following page * will be mapped at the same PMD. We need 2 pages, so find space for 3, diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 39761c7765bd..f5b990e46d7b 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -847,7 +847,8 @@ void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next, * mm_cpumask. The TLB shootdown code can figure out from * cpu_tlbstate_shared.is_lazy whether or not to send an IPI. */ - if (IS_ENABLED(CONFIG_DEBUG_VM) && WARN_ON_ONCE(prev != &init_mm && + if (IS_ENABLED(CONFIG_DEBUG_VM) && + WARN_ON_ONCE(prev != &init_mm && !is_notrack_mm(prev) && !cpumask_test_cpu(cpu, mm_cpumask(next)))) cpumask_set_cpu(cpu, mm_cpumask(next)); |