| Message ID | 2ee707512b8b212b079b877f4ceb525a1606a3fb.1656655567.git.christophe.leroy@csgroup.eu (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 7 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 23 jobs. |
On Fri, 1 Jul 2022 08:06:15 +0200, Christophe Leroy wrote: > Since commit 4291d085b0b0 ("powerpc/32s: Make pte_update() non > atomic on 603 core"), pte_update() has been using > mmu_has_feature(MMU_FTR_HPTE_TABLE) to avoid a useless atomic > operation on 603 cores. > > When kasan_early_init() sets up the early zero shadow, it uses > __set_pte_at(). On book3s/32, __set_pte_at() calls pte_update() > when CONFIG_SMP is selected in order to ensure the preservation of > _PAGE_HASHPTE in case of concurrent update of the PTE. But that's > too early for mmu_has_feature(), so when > CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG is selected, mmu_has_feature() > calls printk(). That's too early to call printk() because KASAN > early zero shadow page is not set up yet. It leads to a deadlock. > > [...] Applied to powerpc/next. [1/1] powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG https://git.kernel.org/powerpc/c/6042a1652d643d1d34fa89bb314cb102960c0800 cheers
diff --git a/arch/powerpc/mm/kasan/init_32.c b/arch/powerpc/mm/kasan/init_32.c index f3e4d069e0ba..a70828a6d935 100644 --- a/arch/powerpc/mm/kasan/init_32.c +++ b/arch/powerpc/mm/kasan/init_32.c @@ -25,7 +25,7 @@ static void __init kasan_populate_pte(pte_t *ptep, pgprot_t prot) int i; for (i = 0; i < PTRS_PER_PTE; i++, ptep++) - __set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 0); + __set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 1); } int __init kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end)
Since commit 4291d085b0b0 ("powerpc/32s: Make pte_update() non atomic on 603 core"), pte_update() has been using mmu_has_feature(MMU_FTR_HPTE_TABLE) to avoid a useless atomic operation on 603 cores. When kasan_early_init() sets up the early zero shadow, it uses __set_pte_at(). On book3s/32, __set_pte_at() calls pte_update() when CONFIG_SMP is selected in order to ensure the preservation of _PAGE_HASHPTE in case of concurrent update of the PTE. But that's too early for mmu_has_feature(), so when CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG is selected, mmu_has_feature() calls printk(). That's too early to call printk() because KASAN early zero shadow page is not set up yet. It leads to a deadlock. However, when kasan_early_init() is called, there is only one CPU running and no risk of concurrent PTE update. So __set_pte_at() can be called with the 'percpu' flag. With that flag set, the PTE is written directly instead of being written via pte_update(). Reported-by: Erhard Furtner <erhard_f@mailbox.org> Fixes: 4291d085b0b0 ("powerpc/32s: Make pte_update() non atomic on 603 core") Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- arch/powerpc/mm/kasan/init_32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)