FAILED: Patch "LoongArch: Disable instrumentation for setup_ptwalker()" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 7cb37af61f09c9cfd90c43c9275307c16320cbf2 Mon Sep 17 00:00:00 2001
From: Tiezhu Yang <[email protected]>
Date: Tue, 10 Feb 2026 19:31:17 +0800
Subject: [PATCH] LoongArch: Disable instrumentation for setup_ptwalker()

According to Documentation/dev-tools/kasan.rst, software KASAN modes use compiler instrumentation to insert validity checks. Such instrumentation might be incompatible with some parts of the kernel, and therefore needs to be disabled, just use the attribute __no_sanitize_address to disable instrumentation for the low level function setup_ptwalker().

Otherwise bringing up the secondary CPUs failed when CONFIG_KASAN is set (especially when PTW is enabled), here are the call chains:

    smpboot_entry()
      start_secondary()
        cpu_probe()
          per_cpu_trap_init()
            tlb_init()
              setup_tlb_handler()
                setup_ptwalker()

The reason is the PGD registers are configured in setup_ptwalker(), but KASAN instrumentation may cause TLB exceptions before that.

Cc [email protected]

Signed-off-by Tiezhu Yang <[email protected]>

Signed-off-by Huacai Chen <[email protected]>

---
 arch/loongarch/mm/tlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

arch/loongarch/mm/tlb.c +1 -2

index 4014c44695878..aaf7d685cc2aa 100644
@@ -202,7 +202,7 @@ void __update_tlb(struct vm_area_struct *vma, unsigned long address, pte_t *ptep
        local_irq_restore(flags);
 }
 
-static void setup_ptwalker(void)
+static void __no_sanitize_address setup_ptwalker(void)
 {
        unsigned long pwctl0, pwctl1;
        unsigned long pgd_i = 0, pgd_w = 0;
--

2.51.0