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a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783950559; bh=hpF+B5I89ietP3twgkdOdoYxWCsb5V0kGzBiAvX1wgs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fEhipLwPpaOlZwwA7uusgOWXnDcZ6crqM6UwSs112vVuANbuv+f94pDG8HL8QZrDM WpoBaqlEh4OT/1Fge7tlsYYRY6DGGBDSouZT32UoHBd6nOSc8LQjA2nlUn7dLwmH2q TTbelgOntgP3R1jjsxOoO4tNvFKkvqY6SsVCHvVE= Message-ID: <85a3a79a-2a78-47ed-bd93-48e8f1967551@arm.com> Date: Mon, 13 Jul 2026 19:19:12 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 4/6] mm/vmalloc: Extend page table walk to support larger page_shift sizes and eliminate page table rewalk To: Wen Jiang , akpm@linux-foundation.org, catalin.marinas@arm.com, linux-mm@kvack.org, urezki@gmail.com, will@kernel.org Cc: Xueyuan.chen21@gmail.com, ajd@linux.ibm.com, anshuman.khandual@arm.com, david@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, rppt@kernel.org, ryan.roberts@arm.com, "Barry Song (Xiaomi)" , Wen Jiang , Leo Yan References: <20260709073823.6643-1-jiangwen6@xiaomi.com> <20260709073823.6643-5-jiangwen6@xiaomi.com> Content-Language: en-US From: Dev Jain In-Reply-To: <20260709073823.6643-5-jiangwen6@xiaomi.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: F131FA0009 X-Stat-Signature: mxo65c3cguoukhxnyd5jrypsi5nrjbjd X-HE-Tag: 1783950560-607334 X-HE-Meta: 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 PppVSJkC SJrimt2YvWho8jHC7cfsxnzyh6F3CBAlkOPugkHAjjV/s+g4jcUIVjMW00nD6QkGG3LVYicVldJv+uZfqoPuysCiJQlbePFBkj6gMTo3wm2ZNOZT8yXzJmjbENHGKEDUF8KnXmB+GhtPOgLzPVsyNLlv3BUXIffj1wWC8ftEK2qAZz1CLHzLpZ8pCCMiYuSj/jdyyyXl9RIZTPP14D3WAlTkaoC74/U4dmm4S2bwVE8BEcGJOYOr3tonO8Ccre8IJhPN3an3m7s9qz0JAX/zTaVYERKs/hS2/5TalKHPhRvJcoZeDWRNgeXPk32W4LGFOwPqWjJ37FIuKqlekcr9HbJgPrIHKqCyIYQabElSeawZA+Ts7gV6lvlCjGgaD52V0YkKgEt8NdCW1ccIEtz7eOZO1i470efeFVjx1lYJGVxk6KCmWIhTaMoNWryuRYKvpxnxJOCEljU0DVsY3MF25oRFJhOTa0e1fsWe8dbz92+wSjZQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09/07/26 1:08 pm, Wen Jiang wrote: > From: "Barry Song (Xiaomi)" > > vmap_pages_range_noflush_walk() (formerly vmap_small_pages_range_noflush()) > provides a clean interface by taking struct page **pages and mapping them > via direct PTE iteration. This avoids the page table rewalk seen when > using vmap_range_noflush() for page_shift values other than PAGE_SHIFT. > > Extend it to support larger page_shift values, and add PMD- and > contiguous-PTE mappings as well. Rename it to vmap_pages_range_noflush_walk() > since it now handles more than just small pages. > > For vmalloc() allocations with VM_ALLOW_HUGE_VMAP, we no longer need to > iterate over pages one by one via vmap_range_noflush(), which would > otherwise lead to page table rewalk. The code is now unified with the > PAGE_SHIFT case by simply calling vmap_pages_range_noflush_walk(). > > Signed-off-by: Barry Song (Xiaomi) > Signed-off-by: Wen Jiang > Tested-by: Xueyuan Chen > Tested-by: Leo Yan > Reviewed-by: Dev Jain > --- > mm/vmalloc.c | 81 ++++++++++++++++++++++++++++++---------------------- > 1 file changed, 47 insertions(+), 34 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index d7fef85b241c4..d2a4d649af549 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -125,7 +125,8 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > pte_t *pte; > u64 pfn; > struct page *page; > - unsigned long size = PAGE_SIZE; > + unsigned long size; > + unsigned int steps; > > if (WARN_ON_ONCE(!PAGE_ALIGNED(end - addr))) > return -EINVAL; > @@ -147,8 +148,8 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > } > > size = vmap_set_ptes(pte, addr, end, pfn, prot, max_page_shift); > - pfn += PFN_DOWN(size); > - } while (pte += PFN_DOWN(size), addr += size, addr != end); > + steps = PFN_DOWN(size); > + } while (pte += steps, pfn += steps, addr += size, addr != end); I think I had also recommended to put these vmap_pte_range() changes into the previous patch. > > lazy_mmu_mode_disable(); > *mask |= PGTBL_PTE_MODIFIED; > @@ -540,8 +541,10 @@ void vunmap_range(unsigned long addr, unsigned long end) > > static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr, > unsigned long end, pgprot_t prot, struct page **pages, int *nr, > - pgtbl_mod_mask *mask) > + pgtbl_mod_mask *mask, unsigned int shift) > { > + unsigned long pfn, size; > + unsigned int steps; > int err = 0; > pte_t *pte; > > @@ -572,9 +575,10 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr, > break; > } > > - set_pte_at(&init_mm, addr, pte, mk_pte(page, prot)); > - (*nr)++; > - } while (pte++, addr += PAGE_SIZE, addr != end); > + pfn = page_to_pfn(page); > + size = vmap_set_ptes(pte, addr, end, pfn, prot, shift); > + steps = PFN_DOWN(size); > + } while (pte += steps, *nr += steps, addr += size, addr != end); > > lazy_mmu_mode_disable(); > *mask |= PGTBL_PTE_MODIFIED; > @@ -584,7 +588,7 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr, > > static int vmap_pages_pmd_range(pud_t *pud, unsigned long addr, > unsigned long end, pgprot_t prot, struct page **pages, int *nr, > - pgtbl_mod_mask *mask) > + pgtbl_mod_mask *mask, unsigned int shift) > { > pmd_t *pmd; > unsigned long next; > @@ -594,7 +598,27 @@ static int vmap_pages_pmd_range(pud_t *pud, unsigned long addr, > return -ENOMEM; > do { > next = pmd_addr_end(addr, end); > - if (vmap_pages_pte_range(pmd, addr, next, prot, pages, nr, mask)) > + > + if (shift >= PMD_SHIFT) { > + struct page *page = pages[*nr]; > + phys_addr_t phys_addr; > + > + if (WARN_ON(!page)) > + return -ENOMEM; > + if (WARN_ON(!pfn_valid(page_to_pfn(page)))) > + return -EINVAL; > + > + phys_addr = page_to_phys(page); > + > + if (vmap_try_huge_pmd(pmd, addr, next, phys_addr, prot, > + shift)) { > + *mask |= PGTBL_PMD_MODIFIED; > + *nr += 1 << (PMD_SHIFT - PAGE_SHIFT); > + continue; > + } > + } > + > + if (vmap_pages_pte_range(pmd, addr, next, prot, pages, nr, mask, shift)) > return -ENOMEM; > } while (pmd++, addr = next, addr != end); > return 0; > @@ -602,7 +626,7 @@ static int vmap_pages_pmd_range(pud_t *pud, unsigned long addr, > > static int vmap_pages_pud_range(p4d_t *p4d, unsigned long addr, > unsigned long end, pgprot_t prot, struct page **pages, int *nr, > - pgtbl_mod_mask *mask) > + pgtbl_mod_mask *mask, unsigned int shift) > { > pud_t *pud; > unsigned long next; > @@ -612,7 +636,7 @@ static int vmap_pages_pud_range(p4d_t *p4d, unsigned long addr, > return -ENOMEM; > do { > next = pud_addr_end(addr, end); > - if (vmap_pages_pmd_range(pud, addr, next, prot, pages, nr, mask)) > + if (vmap_pages_pmd_range(pud, addr, next, prot, pages, nr, mask, shift)) > return -ENOMEM; > } while (pud++, addr = next, addr != end); > return 0; > @@ -620,7 +644,7 @@ static int vmap_pages_pud_range(p4d_t *p4d, unsigned long addr, > > static int vmap_pages_p4d_range(pgd_t *pgd, unsigned long addr, > unsigned long end, pgprot_t prot, struct page **pages, int *nr, > - pgtbl_mod_mask *mask) > + pgtbl_mod_mask *mask, unsigned int shift) > { > p4d_t *p4d; > unsigned long next; > @@ -630,14 +654,18 @@ static int vmap_pages_p4d_range(pgd_t *pgd, unsigned long addr, > return -ENOMEM; > do { > next = p4d_addr_end(addr, end); > - if (vmap_pages_pud_range(p4d, addr, next, prot, pages, nr, mask)) > + if (vmap_pages_pud_range(p4d, addr, next, prot, pages, nr, mask, shift)) > return -ENOMEM; > } while (p4d++, addr = next, addr != end); > return 0; > } > > -static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end, > - pgprot_t prot, struct page **pages) > +/* > + * It can take an array of pages which are not all contiguous, but it > + * may have contiguous chunks, as hinted by @shift. > + */ > +static int vmap_pages_range_noflush_walk(unsigned long addr, unsigned long end, > + pgprot_t prot, struct page **pages, unsigned int shift) > { > unsigned long start = addr; > pgd_t *pgd; > @@ -652,7 +680,7 @@ static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end, > next = pgd_addr_end(addr, end); > if (pgd_bad(*pgd)) > mask |= PGTBL_PGD_MODIFIED; > - err = vmap_pages_p4d_range(pgd, addr, next, prot, pages, &nr, &mask); > + err = vmap_pages_p4d_range(pgd, addr, next, prot, pages, &nr, &mask, shift); > if (err) > break; > } while (pgd++, addr = next, addr != end); > @@ -675,27 +703,12 @@ static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end, > int __vmap_pages_range_noflush(unsigned long addr, unsigned long end, > pgprot_t prot, struct page **pages, unsigned int page_shift) > { > - unsigned int i, nr = (end - addr) >> PAGE_SHIFT; > - > WARN_ON(page_shift < PAGE_SHIFT); > > - if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) || > - page_shift == PAGE_SHIFT) > - return vmap_small_pages_range_noflush(addr, end, prot, pages); > - > - for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) { > - int err; > + if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC)) > + page_shift = PAGE_SHIFT; > > - err = vmap_range_noflush(addr, addr + (1UL << page_shift), > - page_to_phys(pages[i]), prot, > - page_shift); > - if (err) > - return err; > - > - addr += 1UL << page_shift; > - } > - > - return 0; > + return vmap_pages_range_noflush_walk(addr, end, prot, pages, page_shift); > } > > int vmap_pages_range_noflush(unsigned long addr, unsigned long end,