From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B5778C0219D for ; Mon, 10 Feb 2025 11:27:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=aeLvAmxrg/5Ejj7NTrLJNOs2CmzgO1iyfD5lJ+GaPas=; b=VfTHq8u5wSprD4QDL3wmsaahxI 9jM5HXI+GsPKEO6eu90zYnG4mlGlojOXhCPnWM3xXS5K8ZAa6zEWPd9wkMRqFTdGEh+dkiFfOHuKJ E7qZxMQ0SZTauuCSp+OYw3s8HOuC3A+xvesPgCDnZyFxnBR/byIourFkzTvTD0eyqmhYHL4e4gZYk GKGBGUgxkAT3edtYCk6VU9gZmwDB0BKDn0U76TAFiHWxe7q++mff5YYoqnO7ghzot2XS/IWyYpItP 82+fjh05JwHWORNgD57dja2gkR2+TOZSkFM2LOetetVnX+5MdUmAMjvC9P/Kf+ZMRD0D1gwC5B+nQ 2k5aBpug==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1thRwb-0000000HDDO-3wOJ; Mon, 10 Feb 2025 11:27:17 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1thRb5-0000000H8jn-0VH1 for linux-arm-kernel@lists.infradead.org; Mon, 10 Feb 2025 11:05:04 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DC26F1BC0; Mon, 10 Feb 2025 03:05:21 -0800 (PST) Received: from [10.57.81.206] (unknown [10.57.81.206]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7A7193F5A1; Mon, 10 Feb 2025 03:04:57 -0800 (PST) Message-ID: Date: Mon, 10 Feb 2025 11:04:55 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 15/16] mm: Generalize arch_sync_kernel_mappings() To: Anshuman Khandual , Catalin Marinas , Will Deacon , Muchun Song , Pasha Tatashin , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Mark Rutland , Ard Biesheuvel , Dev Jain , Alexandre Ghiti , Steve Capper , Kevin Brodsky Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250205151003.88959-1-ryan.roberts@arm.com> <20250205151003.88959-16-ryan.roberts@arm.com> <43c256b6-7e44-41bb-b0c5-866fd4faab5c@arm.com> Content-Language: en-GB From: Ryan Roberts In-Reply-To: <43c256b6-7e44-41bb-b0c5-866fd4faab5c@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250210_030503_248626_6C3E004A X-CRM114-Status: GOOD ( 37.63 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 10/02/2025 07:45, Anshuman Khandual wrote: > > > On 2/5/25 20:39, Ryan Roberts wrote: >> arch_sync_kernel_mappings() is an optional hook for arches to allow them >> to synchonize certain levels of the kernel pgtables after modification. >> But arm64 could benefit from a hook similar to this, paired with a call >> prior to starting the batch of modifications. >> >> So let's introduce arch_update_kernel_mappings_begin() and >> arch_update_kernel_mappings_end(). Both have a default implementation >> which can be overridden by the arch code. The default for the former is >> a nop, and the default for the latter is to call >> arch_sync_kernel_mappings(), so the latter replaces previous >> arch_sync_kernel_mappings() callsites. So by default, the resulting >> behaviour is unchanged. >> >> To avoid include hell, the pgtbl_mod_mask type and it's associated >> macros are moved to their own header. >> >> In a future patch, arm64 will opt-in to overriding both functions. >> >> Signed-off-by: Ryan Roberts >> --- >> include/linux/pgtable.h | 24 +---------------- >> include/linux/pgtable_modmask.h | 32 ++++++++++++++++++++++ >> include/linux/vmalloc.h | 47 +++++++++++++++++++++++++++++++++ >> mm/memory.c | 5 ++-- >> mm/vmalloc.c | 15 ++++++----- >> 5 files changed, 92 insertions(+), 31 deletions(-) >> create mode 100644 include/linux/pgtable_modmask.h >> >> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >> index 94d267d02372..7f70786a73b3 100644 >> --- a/include/linux/pgtable.h >> +++ b/include/linux/pgtable.h >> @@ -4,6 +4,7 @@ >> >> #include >> #include >> +#include >> >> #define PMD_ORDER (PMD_SHIFT - PAGE_SHIFT) >> #define PUD_ORDER (PUD_SHIFT - PAGE_SHIFT) >> @@ -1786,29 +1787,6 @@ static inline bool arch_has_pfn_modify_check(void) >> # define PAGE_KERNEL_EXEC PAGE_KERNEL >> #endif >> >> -/* >> - * Page Table Modification bits for pgtbl_mod_mask. >> - * >> - * These are used by the p?d_alloc_track*() set of functions an in the generic >> - * vmalloc/ioremap code to track at which page-table levels entries have been >> - * modified. Based on that the code can better decide when vmalloc and ioremap >> - * mapping changes need to be synchronized to other page-tables in the system. >> - */ >> -#define __PGTBL_PGD_MODIFIED 0 >> -#define __PGTBL_P4D_MODIFIED 1 >> -#define __PGTBL_PUD_MODIFIED 2 >> -#define __PGTBL_PMD_MODIFIED 3 >> -#define __PGTBL_PTE_MODIFIED 4 >> - >> -#define PGTBL_PGD_MODIFIED BIT(__PGTBL_PGD_MODIFIED) >> -#define PGTBL_P4D_MODIFIED BIT(__PGTBL_P4D_MODIFIED) >> -#define PGTBL_PUD_MODIFIED BIT(__PGTBL_PUD_MODIFIED) >> -#define PGTBL_PMD_MODIFIED BIT(__PGTBL_PMD_MODIFIED) >> -#define PGTBL_PTE_MODIFIED BIT(__PGTBL_PTE_MODIFIED) >> - >> -/* Page-Table Modification Mask */ >> -typedef unsigned int pgtbl_mod_mask; >> - >> #endif /* !__ASSEMBLY__ */ >> >> #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT) >> diff --git a/include/linux/pgtable_modmask.h b/include/linux/pgtable_modmask.h >> new file mode 100644 >> index 000000000000..5a21b1bb8df3 >> --- /dev/null >> +++ b/include/linux/pgtable_modmask.h >> @@ -0,0 +1,32 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#ifndef _LINUX_PGTABLE_MODMASK_H >> +#define _LINUX_PGTABLE_MODMASK_H >> + >> +#ifndef __ASSEMBLY__ >> + >> +/* >> + * Page Table Modification bits for pgtbl_mod_mask. >> + * >> + * These are used by the p?d_alloc_track*() set of functions an in the generic >> + * vmalloc/ioremap code to track at which page-table levels entries have been >> + * modified. Based on that the code can better decide when vmalloc and ioremap >> + * mapping changes need to be synchronized to other page-tables in the system. >> + */ >> +#define __PGTBL_PGD_MODIFIED 0 >> +#define __PGTBL_P4D_MODIFIED 1 >> +#define __PGTBL_PUD_MODIFIED 2 >> +#define __PGTBL_PMD_MODIFIED 3 >> +#define __PGTBL_PTE_MODIFIED 4 >> + >> +#define PGTBL_PGD_MODIFIED BIT(__PGTBL_PGD_MODIFIED) >> +#define PGTBL_P4D_MODIFIED BIT(__PGTBL_P4D_MODIFIED) >> +#define PGTBL_PUD_MODIFIED BIT(__PGTBL_PUD_MODIFIED) >> +#define PGTBL_PMD_MODIFIED BIT(__PGTBL_PMD_MODIFIED) >> +#define PGTBL_PTE_MODIFIED BIT(__PGTBL_PTE_MODIFIED) >> + >> +/* Page-Table Modification Mask */ >> +typedef unsigned int pgtbl_mod_mask; >> + >> +#endif /* !__ASSEMBLY__ */ >> + >> +#endif /* _LINUX_PGTABLE_MODMASK_H */ >> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h >> index 16dd4cba64f2..cb5d8f1965a1 100644 >> --- a/include/linux/vmalloc.h >> +++ b/include/linux/vmalloc.h >> @@ -11,6 +11,7 @@ >> #include /* pgprot_t */ >> #include >> #include >> +#include >> >> #include >> >> @@ -213,6 +214,26 @@ extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr, >> int vmap_pages_range(unsigned long addr, unsigned long end, pgprot_t prot, >> struct page **pages, unsigned int page_shift); >> >> +#ifndef arch_update_kernel_mappings_begin >> +/** >> + * arch_update_kernel_mappings_begin - A batch of kernel pgtable mappings are >> + * about to be updated. >> + * @start: Virtual address of start of range to be updated. >> + * @end: Virtual address of end of range to be updated. >> + * >> + * An optional hook to allow architecture code to prepare for a batch of kernel >> + * pgtable mapping updates. An architecture may use this to enter a lazy mode >> + * where some operations can be deferred until the end of the batch. >> + * >> + * Context: Called in task context and may be preemptible. >> + */ >> +static inline void arch_update_kernel_mappings_begin(unsigned long start, >> + unsigned long end) >> +{ >> +} >> +#endif >> + >> +#ifndef arch_update_kernel_mappings_end >> /* >> * Architectures can set this mask to a combination of PGTBL_P?D_MODIFIED values >> * and let generic vmalloc and ioremap code know when arch_sync_kernel_mappings() >> @@ -229,6 +250,32 @@ int vmap_pages_range(unsigned long addr, unsigned long end, pgprot_t prot, >> */ >> void arch_sync_kernel_mappings(unsigned long start, unsigned long end); >> >> +/** >> + * arch_update_kernel_mappings_end - A batch of kernel pgtable mappings have >> + * been updated. >> + * @start: Virtual address of start of range that was updated. >> + * @end: Virtual address of end of range that was updated. >> + * >> + * An optional hook to inform architecture code that a batch update is complete. >> + * This balances a previous call to arch_update_kernel_mappings_begin(). >> + * >> + * An architecture may override this for any purpose, such as exiting a lazy >> + * mode previously entered with arch_update_kernel_mappings_begin() or syncing >> + * kernel mappings to a secondary pgtable. The default implementation calls an >> + * arch-provided arch_sync_kernel_mappings() if any arch-defined pgtable level >> + * was updated. >> + * >> + * Context: Called in task context and may be preemptible. >> + */ >> +static inline void arch_update_kernel_mappings_end(unsigned long start, >> + unsigned long end, >> + pgtbl_mod_mask mask) >> +{ >> + if (mask & ARCH_PAGE_TABLE_SYNC_MASK) >> + arch_sync_kernel_mappings(start, end); >> +} > > One arch call back calling yet another arch call back sounds bit odd. It's no different from the default implementation of arch_make_huge_pte() calling pte_mkhuge() is it? > Also > should not ARCH_PAGE_TABLE_SYNC_MASK be checked both for __begin and __end > callbacks in case a platform subscribes into this framework. I'm not sure how that would work? The mask is accumulated during the pgtable walk. So we don't have a mask until we get to the end. > Instead the > following changes sound more reasonable, but will also require some more > updates for the current platforms using arch_sync_kernel_mappings(). > > if (mask & ARCH_PAGE_TABLE_SYNC_MASK) > arch_update_kernel_mappings_begin() This makes no sense. mask is always 0 before doing the walk. > > if (mask & ARCH_PAGE_TABLE_SYNC_MASK) > arch_update_kernel_mappings_end() > > Basically when any platform defines ARCH_PAGE_TABLE_SYNC_MASK and subscribes > this framework, it will also provide arch_update_kernel_mappings_begin/end() > callbacks as required. Personally I think it's cleaner to just pass mask to arch_update_kernel_mappings_end() and it the function decide what it wants to do. But it's a good question as to whether we should refactor x86 and arm to directly implement arch_update_kernel_mappings_end() instead of arch_sync_kernel_mappings(). Personally I thought it was better to avoid the churn. But interested in others opinions. Thanks, Ryan > >> +#endif >> + >> /* >> * Lowlevel-APIs (not for driver use!) >> */ >> diff --git a/mm/memory.c b/mm/memory.c >> index a15f7dd500ea..f80930bc19f6 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -3035,6 +3035,8 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr, >> if (WARN_ON(addr >= end)) >> return -EINVAL; >> >> + arch_update_kernel_mappings_begin(start, end); >> + >> pgd = pgd_offset(mm, addr); >> do { >> next = pgd_addr_end(addr, end); >> @@ -3055,8 +3057,7 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr, >> break; >> } while (pgd++, addr = next, addr != end); >> >> - if (mask & ARCH_PAGE_TABLE_SYNC_MASK) >> - arch_sync_kernel_mappings(start, start + size); >> + arch_update_kernel_mappings_end(start, end, mask); >> >> return err; >> } >> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >> index 50fd44439875..c5c51d86ef78 100644 >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -312,10 +312,10 @@ int vmap_page_range(unsigned long addr, unsigned long end, >> pgtbl_mod_mask mask = 0; >> int err; >> >> + arch_update_kernel_mappings_begin(addr, end); >> err = vmap_range_noflush(addr, end, phys_addr, pgprot_nx(prot), >> ioremap_max_page_shift, &mask); >> - if (mask & ARCH_PAGE_TABLE_SYNC_MASK) >> - arch_sync_kernel_mappings(addr, end); >> + arch_update_kernel_mappings_end(addr, end, mask); >> >> flush_cache_vmap(addr, end); >> if (!err) >> @@ -463,6 +463,9 @@ void __vunmap_range_noflush(unsigned long start, unsigned long end) >> pgtbl_mod_mask mask = 0; >> >> BUG_ON(addr >= end); >> + >> + arch_update_kernel_mappings_begin(start, end); >> + >> pgd = pgd_offset_k(addr); >> do { >> next = pgd_addr_end(addr, end); >> @@ -473,8 +476,7 @@ void __vunmap_range_noflush(unsigned long start, unsigned long end) >> vunmap_p4d_range(pgd, addr, next, &mask); >> } while (pgd++, addr = next, addr != end); >> >> - if (mask & ARCH_PAGE_TABLE_SYNC_MASK) >> - arch_sync_kernel_mappings(start, end); >> + arch_update_kernel_mappings_end(start, end, mask); >> } >> >> void vunmap_range_noflush(unsigned long start, unsigned long end) >> @@ -625,6 +627,8 @@ int __vmap_pages_range_noflush(unsigned long addr, unsigned long end, >> >> WARN_ON(page_shift < PAGE_SHIFT); >> >> + arch_update_kernel_mappings_begin(start, end); >> + >> if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) || >> page_shift == PAGE_SHIFT) { >> err = vmap_small_pages_range_noflush(addr, end, prot, pages, >> @@ -642,8 +646,7 @@ int __vmap_pages_range_noflush(unsigned long addr, unsigned long end, >> } >> } >> >> - if (mask & ARCH_PAGE_TABLE_SYNC_MASK) >> - arch_sync_kernel_mappings(start, end); >> + arch_update_kernel_mappings_end(start, end, mask); >> >> return err; >> }