From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1B2C342DFF5 for ; Mon, 13 Jul 2026 14:34:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783953244; cv=none; b=J7Ul54JE2PRZwqzQ/41qjtE0gYcV5u5MsHpSENVx0nIyKd0u0Nhc/x44qjAC52dDH04u6+ObhcChc/ALU/kYeOG32ll6Xno3/U95km3tj1kivrAMxeiWj7oI3BjaKsX3cREQDys846psVzkKA17dZ7tW0e5YRYfpwOecv7atsh4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783953244; c=relaxed/simple; bh=z/sxrbHtKq47+tn7wnaajtQLPGy1vUnWOLQH+8bLcms=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=FNQ4VphBNzxAfdSs8fDpGKOL7CQ2Nq2xAT80QGPLCrnPseLV1WXkvBvEkv4gLHQ7Klb76MJlNGPjVQWN/wS9Rb5V/5y5pKFouqWGHqrhgM5V+gzRTY3qd1c4EZhEhYlMStRLhUcZHmAEU+rDpqs0bgUluN1V8H74kL+Gr60Gj4o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=R4omjCxf; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="R4omjCxf" 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 4E07F152B; Mon, 13 Jul 2026 07:33:57 -0700 (PDT) Received: from [10.164.19.52] (unknown [10.164.19.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 36A873F7B4; Mon, 13 Jul 2026 07:33:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783953241; bh=z/sxrbHtKq47+tn7wnaajtQLPGy1vUnWOLQH+8bLcms=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=R4omjCxfVxmDHk1dI2d+pVNOx18dC4n7dIfnILoLKWOPDOmI4W9aXDvYLeieZijdg N0NBuSTI/3SD7rxvaqAvANvjSz0Ocnom2pbOuE8KLDiXFTmZLVwaoip2Fiapd6TnOP 3nfLhSMqaI9PbKdcPrIWBGU2W+lqkgr4cXc8qYMY= Message-ID: <4f8a2ed1-109b-4d64-af49-31b50493fd12@arm.com> Date: Mon, 13 Jul 2026 20:03:54 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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); > > 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; You will have to propagate the error from vmap_pages_pte_range. > } 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; And here > } 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; And here > } 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,