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d=hostedemail.com; s=arc-20220608; t=1729232553; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IS+NMHaCLJDhf0HKE2ebm54p21Ok6Av5jM3ADqBkHRQ=; b=GAN5xSp7JaMyEv7Y9wDFEcVa9FdCn6qAS1aeDTufXCYkVKeiexd1BRGVKZ0xx2wqwniUQZ 79yhuw3fB6UgRq3LkcxVEh1s8ZWcyu2fbTjncOmVj4uTzQKMFwo0M/JpWKVnuQv6MZ8bNK N9GEgASX8kZV2q8GBLcBDtgkNn71A70= Received: from loongson.cn (unknown [10.20.42.62]) by gateway (Coremail) with SMTP id _____8Axjuvs_hFnyWsjAA--.50795S3; Fri, 18 Oct 2024 14:23:40 +0800 (CST) Received: from [10.20.42.62] (unknown [10.20.42.62]) by front1 (Coremail) with SMTP id qMiowMAxSebi_hFn8IEvAA--.29158S3; Fri, 18 Oct 2024 14:23:33 +0800 (CST) Subject: Re: [PATCH v2 1/3] LoongArch: Set initial pte entry with PAGE_GLOBAL for kernel space To: Huacai Chen , wuruiyang@loongson.cn Cc: Andrey Ryabinin , Andrew Morton , David Hildenbrand , Barry Song , loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org References: <20241014035855.1119220-1-maobibo@loongson.cn> <20241014035855.1119220-2-maobibo@loongson.cn> From: maobibo Message-ID: <5f76ede6-e8be-c7a9-f957-479afa2fb828@loongson.cn> Date: Fri, 18 Oct 2024 14:23:11 +0800 User-Agent: Mozilla/5.0 (X11; Linux loongarch64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-CM-TRANSID:qMiowMAxSebi_hFn8IEvAA--.29158S3 X-CM-SenderInfo: xpdruxter6z05rqj20fqof0/ X-Coremail-Antispam: 1Uk129KBj93XoW3try8Xr4fAF45Wr1DZFWUAwc_yoWkAw1Upr yDCF1kAF4UXr1UJwsFqw1jqrnrtwn7KF4IgF17Gr15AFnFqFnrJr1UJry5uF18J3yUG3W0 vr1rKw13WF1UJ3cCm3ZEXasCq-sJn29KB7ZKAUJUUUU8529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUvIb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Jr0_JF4l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Jr0_Gr1l84ACjcxK6I8E87Iv67AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVCY1x0267AK xVW8Jr0_Cr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l57IF6xkI12xvs2x26I8E6xACxx 1l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r106r15McIj6I8E87Iv 67AKxVW8JVWxJwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lc7I2V7IY0VAS07 AlzVAYIcxG8wCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02 F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GF ylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7Cj xVAFwI0_Jr0_Gr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r 4j6F4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07jn UUUUUUUU= X-Stat-Signature: qwehbazu6w8aj7hyngphjzjx6f3rnbgw X-Rspamd-Queue-Id: 629671C0006 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1729232605-34165 X-HE-Meta: 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 Wt0W8uwu 7u7I2TpB2eHOd/kDL+l5Gd2lpO+wWpRrMh8SI8D9/Y0SvJlLuOx0WDxojbLi3Y2JeTKgssRgC4ttg+XE/yJKelqRHRPWdET0kL8pA0wjjM7Js63jH7uozQDm6K2KXBZ/7PltnrZBMD+xJaJ00T9/LNPPyF9p8SNjaosC64olKZvhxjBjJtm9Z9CMEZEM+hP+0ZosTemYGbct4pNSYhRClmKyU+Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024/10/18 下午12:23, Huacai Chen wrote: > On Fri, Oct 18, 2024 at 12:16 PM maobibo wrote: >> >> >> >> On 2024/10/18 下午12:11, Huacai Chen wrote: >>> On Fri, Oct 18, 2024 at 11:44 AM maobibo 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. Also from Ruiyang Wu, the information is that speculative accesses may insert stale TLB, however no page fault exception. So adding barrier in set_pte() does not prevent speculative accesses. And you write patch here, however do not know the actual reason? https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.12-rc3&id=f93f67d06b1023313ef1662eac490e29c025c030 Bibo Mao > > 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 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 >>>>>> --- >>>>>> 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 >>>>>> >>>>>> +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 >>>>>> >>>> >>>> >> >>