On Fri, Oct 18, 2024 at 12:16 PM maobibo <maobibo@xxxxxxxxxxx> wrote: > > > > On 2024/10/18 下午12:11, Huacai Chen wrote: > > On Fri, Oct 18, 2024 at 11:44 AM maobibo <maobibo@xxxxxxxxxxx> wrote: > >> > >> > >> > >> On 2024/10/18 上午11:14, Huacai Chen wrote: > >>> Hi, Bibo, > >>> > >>> I applied this patch but drop the part of arch/loongarch/mm/kasan_init.c: > >>> https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson.git/commit/?h=loongarch-next&id=15832255e84494853f543b4c70ced50afc403067 > >>> > >>> Because kernel_pte_init() should operate on page-table pages, not on > >>> data pages. You have already handle page-table page in > >>> mm/kasan/init.c, and if we don't drop the modification on data pages > >>> in arch/loongarch/mm/kasan_init.c, the kernel fail to boot if KASAN is > >>> enabled. > >>> > >> static inline void set_pte(pte_t *ptep, pte_t pteval) > >> { > >> WRITE_ONCE(*ptep, pteval); > >> - > >> - if (pte_val(pteval) & _PAGE_GLOBAL) { > >> - pte_t *buddy = ptep_buddy(ptep); > >> - /* > >> - * Make sure the buddy is global too (if it's !none, > >> - * it better already be global) > >> - */ > >> - if (pte_none(ptep_get(buddy))) { > >> -#ifdef CONFIG_SMP > >> - /* > >> - * For SMP, multiple CPUs can race, so we need > >> - * to do this atomically. > >> - */ > >> - __asm__ __volatile__( > >> - __AMOR "$zero, %[global], %[buddy] \n" > >> - : [buddy] "+ZB" (buddy->pte) > >> - : [global] "r" (_PAGE_GLOBAL) > >> - : "memory"); > >> - > >> - DBAR(0b11000); /* o_wrw = 0b11000 */ > >> -#else /* !CONFIG_SMP */ > >> - WRITE_ONCE(*buddy, __pte(pte_val(ptep_get(buddy)) | _PAGE_GLOBAL)); > >> -#endif /* CONFIG_SMP */ > >> - } > >> - } > >> + DBAR(0b11000); /* o_wrw = 0b11000 */ > >> } > >> > >> No, please hold on. This issue exists about twenty years, Do we need be > >> in such a hurry now? > >> > >> why is DBAR(0b11000) added in set_pte()? > > It exists before, not added by this patch. The reason is explained in > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.12-rc3&id=f93f67d06b1023313ef1662eac490e29c025c030 > why speculative accesses may cause spurious page fault in kernel space > with PTE enabled? speculative accesses exists anywhere, it does not > cause spurious page fault. Confirmed by Ruiyang Wu, and even if DBAR(0b11000) is wrong, that means another patch's mistake, not this one. This one just keeps the old behavior. +CC Ruiyang Wu here. Huacai > > Obvious you do not it and you write wrong patch. > > > > > Huacai > > > >> > >> Regards > >> Bibo Mao > >>> Huacai > >>> > >>> On Mon, Oct 14, 2024 at 11:59 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote: > >>>> > >>>> Unlike general architectures, there are two pages in one TLB entry > >>>> on LoongArch system. For kernel space, it requires both two pte > >>>> entries with PAGE_GLOBAL bit set, else HW treats it as non-global > >>>> tlb, there will be potential problems if tlb entry for kernel space > >>>> is not global. Such as fail to flush kernel tlb with function > >>>> local_flush_tlb_kernel_range() which only flush tlb with global bit. > >>>> > >>>> With function kernel_pte_init() added, it can be used to init pte > >>>> table when it is created for kernel address space, and the default > >>>> initial pte value is PAGE_GLOBAL rather than zero at beginning. > >>>> > >>>> Kernel address space areas includes fixmap, percpu, vmalloc, kasan > >>>> and vmemmap areas set default pte entry with PAGE_GLOBAL set. > >>>> > >>>> Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx> > >>>> --- > >>>> arch/loongarch/include/asm/pgalloc.h | 13 +++++++++++++ > >>>> arch/loongarch/include/asm/pgtable.h | 1 + > >>>> arch/loongarch/mm/init.c | 4 +++- > >>>> arch/loongarch/mm/kasan_init.c | 4 +++- > >>>> arch/loongarch/mm/pgtable.c | 22 ++++++++++++++++++++++ > >>>> include/linux/mm.h | 1 + > >>>> mm/kasan/init.c | 8 +++++++- > >>>> mm/sparse-vmemmap.c | 5 +++++ > >>>> 8 files changed, 55 insertions(+), 3 deletions(-) > >>>> > >>>> diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h > >>>> index 4e2d6b7ca2ee..b2698c03dc2c 100644 > >>>> --- a/arch/loongarch/include/asm/pgalloc.h > >>>> +++ b/arch/loongarch/include/asm/pgalloc.h > >>>> @@ -10,8 +10,21 @@ > >>>> > >>>> #define __HAVE_ARCH_PMD_ALLOC_ONE > >>>> #define __HAVE_ARCH_PUD_ALLOC_ONE > >>>> +#define __HAVE_ARCH_PTE_ALLOC_ONE_KERNEL > >>>> #include <asm-generic/pgalloc.h> > >>>> > >>>> +static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm) > >>>> +{ > >>>> + pte_t *pte; > >>>> + > >>>> + pte = (pte_t *) __get_free_page(GFP_KERNEL); > >>>> + if (!pte) > >>>> + return NULL; > >>>> + > >>>> + kernel_pte_init(pte); > >>>> + return pte; > >>>> +} > >>>> + > >>>> static inline void pmd_populate_kernel(struct mm_struct *mm, > >>>> pmd_t *pmd, pte_t *pte) > >>>> { > >>>> diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h > >>>> index 9965f52ef65b..22e3a8f96213 100644 > >>>> --- a/arch/loongarch/include/asm/pgtable.h > >>>> +++ b/arch/loongarch/include/asm/pgtable.h > >>>> @@ -269,6 +269,7 @@ extern void set_pmd_at(struct mm_struct *mm, unsigned long addr, pmd_t *pmdp, pm > >>>> extern void pgd_init(void *addr); > >>>> extern void pud_init(void *addr); > >>>> extern void pmd_init(void *addr); > >>>> +extern void kernel_pte_init(void *addr); > >>>> > >>>> /* > >>>> * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that > >>>> diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c > >>>> index 8a87a482c8f4..9f26e933a8a3 100644 > >>>> --- a/arch/loongarch/mm/init.c > >>>> +++ b/arch/loongarch/mm/init.c > >>>> @@ -198,9 +198,11 @@ pte_t * __init populate_kernel_pte(unsigned long addr) > >>>> if (!pmd_present(pmdp_get(pmd))) { > >>>> pte_t *pte; > >>>> > >>>> - pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE); > >>>> + pte = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE); > >>>> if (!pte) > >>>> panic("%s: Failed to allocate memory\n", __func__); > >>>> + > >>>> + kernel_pte_init(pte); > >>>> pmd_populate_kernel(&init_mm, pmd, pte); > >>>> } > >>>> > >>>> diff --git a/arch/loongarch/mm/kasan_init.c b/arch/loongarch/mm/kasan_init.c > >>>> index 427d6b1aec09..34988573b0d5 100644 > >>>> --- a/arch/loongarch/mm/kasan_init.c > >>>> +++ b/arch/loongarch/mm/kasan_init.c > >>>> @@ -152,6 +152,8 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr, > >>>> phys_addr_t page_phys = early ? > >>>> __pa_symbol(kasan_early_shadow_page) > >>>> : kasan_alloc_zeroed_page(node); > >>>> + if (!early) > >>>> + kernel_pte_init(__va(page_phys)); > >>>> next = addr + PAGE_SIZE; > >>>> set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL)); > >>>> } while (ptep++, addr = next, addr != end && __pte_none(early, ptep_get(ptep))); > >>>> @@ -287,7 +289,7 @@ void __init kasan_init(void) > >>>> set_pte(&kasan_early_shadow_pte[i], > >>>> pfn_pte(__phys_to_pfn(__pa_symbol(kasan_early_shadow_page)), PAGE_KERNEL_RO)); > >>>> > >>>> - memset(kasan_early_shadow_page, 0, PAGE_SIZE); > >>>> + kernel_pte_init(kasan_early_shadow_page); > >>>> csr_write64(__pa_symbol(swapper_pg_dir), LOONGARCH_CSR_PGDH); > >>>> local_flush_tlb_all(); > >>>> > >>>> diff --git a/arch/loongarch/mm/pgtable.c b/arch/loongarch/mm/pgtable.c > >>>> index eb6a29b491a7..228ffc1db0a3 100644 > >>>> --- a/arch/loongarch/mm/pgtable.c > >>>> +++ b/arch/loongarch/mm/pgtable.c > >>>> @@ -38,6 +38,28 @@ pgd_t *pgd_alloc(struct mm_struct *mm) > >>>> } > >>>> EXPORT_SYMBOL_GPL(pgd_alloc); > >>>> > >>>> +void kernel_pte_init(void *addr) > >>>> +{ > >>>> + unsigned long *p, *end; > >>>> + unsigned long entry; > >>>> + > >>>> + entry = (unsigned long)_PAGE_GLOBAL; > >>>> + p = (unsigned long *)addr; > >>>> + end = p + PTRS_PER_PTE; > >>>> + > >>>> + do { > >>>> + p[0] = entry; > >>>> + p[1] = entry; > >>>> + p[2] = entry; > >>>> + p[3] = entry; > >>>> + p[4] = entry; > >>>> + p += 8; > >>>> + p[-3] = entry; > >>>> + p[-2] = entry; > >>>> + p[-1] = entry; > >>>> + } while (p != end); > >>>> +} > >>>> + > >>>> void pgd_init(void *addr) > >>>> { > >>>> unsigned long *p, *end; > >>>> diff --git a/include/linux/mm.h b/include/linux/mm.h > >>>> index ecf63d2b0582..6909fe059a2c 100644 > >>>> --- a/include/linux/mm.h > >>>> +++ b/include/linux/mm.h > >>>> @@ -3818,6 +3818,7 @@ void *sparse_buffer_alloc(unsigned long size); > >>>> struct page * __populate_section_memmap(unsigned long pfn, > >>>> unsigned long nr_pages, int nid, struct vmem_altmap *altmap, > >>>> struct dev_pagemap *pgmap); > >>>> +void kernel_pte_init(void *addr); > >>>> void pmd_init(void *addr); > >>>> void pud_init(void *addr); > >>>> pgd_t *vmemmap_pgd_populate(unsigned long addr, int node); > >>>> diff --git a/mm/kasan/init.c b/mm/kasan/init.c > >>>> index 89895f38f722..ac607c306292 100644 > >>>> --- a/mm/kasan/init.c > >>>> +++ b/mm/kasan/init.c > >>>> @@ -106,6 +106,10 @@ static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr, > >>>> } > >>>> } > >>>> > >>>> +void __weak __meminit kernel_pte_init(void *addr) > >>>> +{ > >>>> +} > >>>> + > >>>> static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr, > >>>> unsigned long end) > >>>> { > >>>> @@ -126,8 +130,10 @@ static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr, > >>>> > >>>> if (slab_is_available()) > >>>> p = pte_alloc_one_kernel(&init_mm); > >>>> - else > >>>> + else { > >>>> p = early_alloc(PAGE_SIZE, NUMA_NO_NODE); > >>>> + kernel_pte_init(p); > >>>> + } > >>>> if (!p) > >>>> return -ENOMEM; > >>>> > >>>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c > >>>> index edcc7a6b0f6f..c0388b2e959d 100644 > >>>> --- a/mm/sparse-vmemmap.c > >>>> +++ b/mm/sparse-vmemmap.c > >>>> @@ -184,6 +184,10 @@ static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node) > >>>> return p; > >>>> } > >>>> > >>>> +void __weak __meminit kernel_pte_init(void *addr) > >>>> +{ > >>>> +} > >>>> + > >>>> pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node) > >>>> { > >>>> pmd_t *pmd = pmd_offset(pud, addr); > >>>> @@ -191,6 +195,7 @@ pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node) > >>>> void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); > >>>> if (!p) > >>>> return NULL; > >>>> + kernel_pte_init(p); > >>>> pmd_populate_kernel(&init_mm, pmd, p); > >>>> } > >>>> return pmd; > >>>> -- > >>>> 2.39.3 > >>>> > >> > >> > >
