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 7763F282F27 for ; Wed, 27 May 2026 05:59:04 +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=1779861546; cv=none; b=mo76CeUbr7x13k95mGEuLmOwCMLhTYrgiavffqsMmTE+sZEemeA64Z8tNCfhhKi5niHQYR+oEX4+QRahDVD1i3sAoWWXAIkRskQb/rHiYKUXECypX23rcezarIn+eodgVutpt1CUuhKEqKgWaKIMooByB4uJ6i3EAInGeQzuYlI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779861546; c=relaxed/simple; bh=ouSFEB5JSyxfV8CdG4ob7/ZqkwxxEzp2bArEI1XtNEw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Z2/+K+z5QQIUsc8uNjnGPWRWxWeOiNDtol8894YfsZF9f3b3aBjnIDjXehbw1zJDfzAfXq/LdUVd1zRHsndEAjTKAzDuMDjyVDni98Y6hpkegcyGD99F4GL0PEYI+hyTxr0syLYJLGWf40dz/qjWRmmzr+rTZS5SK+yqTfE+S7k= 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=d2/4xwkH; 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="d2/4xwkH" 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 84A3616F2; Tue, 26 May 2026 22:58:58 -0700 (PDT) Received: from [10.164.19.7] (unknown [10.164.19.7]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 95A003F632; Tue, 26 May 2026 22:58:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1779861543; bh=ouSFEB5JSyxfV8CdG4ob7/ZqkwxxEzp2bArEI1XtNEw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=d2/4xwkHi/rrZvxRu4hDCdxSAU5SxTUdtgVX+1V0pDhGBkT0h9kG+l+RXSh1cpfKG Xlat8gq3hwPNWvd/iFhHO5U68tFwryMc4yBD/JeTsBIi1FsakSeaVDr68BT8Pe4+q/ Fqj2xTuMqZchX/LHfzZMCywT632O3Bjh7rSk2oNo= Message-ID: <46b0f2a7-3c0d-4372-a45d-946d8259d410@arm.com> Date: Wed, 27 May 2026 11:28:55 +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 v3 4/6] mm/vmalloc: Extend page table walk to support larger page_shift sizes and eliminate page table rewalk To: Wen Jiang , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, urezki@gmail.com Cc: baohua@kernel.org, Xueyuan.chen21@gmail.com, rppt@kernel.org, david@kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, ajd@linux.ibm.com, linux-kernel@vger.kernel.org, jiangwen6@xiaomi.com References: <20260522053146.83209-1-jiangwenxiaomi@gmail.com> <20260522053146.83209-5-jiangwenxiaomi@gmail.com> Content-Language: en-US From: Dev Jain In-Reply-To: <20260522053146.83209-5-jiangwenxiaomi@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 22/05/26 11:01 am, 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 > --- > mm/vmalloc.c | 71 +++++++++++++++++++++++++++++----------------------- > 1 file changed, 40 insertions(+), 31 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 53fd4ee460ea4..deb764abc0571 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -543,8 +543,10 @@ 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; > > @@ -575,9 +577,10 @@ 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; > @@ -587,7 +590,7 @@ 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; > @@ -597,7 +600,27 @@ 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; So I know these !page and !pfn_valid checks have been copied from vmap_pages_pte_range, but do they mean anything? I think pfn_valid() makes sense in that someone may take a random VA/PA, convert it into a struct page and pass to vmap layer. But I don't see how anyone would pass page == NULL? At the very least, returning ENOMEM does not make sense because the pages are not being allocated by vmap() but have already been allocated. > + > + phys_addr = page_to_phys(page); > + > + if (vmap_try_huge_pmd(pmd, addr, next, phys_addr, prot, > + shift)) { > + *mask |= PGTBL_PMD_MODIFIED; > + *nr += 1 << (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; > @@ -605,7 +628,7 @@ 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; > @@ -615,7 +638,7 @@ 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; > @@ -623,7 +646,7 @@ 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; > @@ -633,14 +656,14 @@ 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) > +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; > @@ -655,7 +678,7 @@ 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); > @@ -678,27 +701,13 @@ 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); > + if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC)) > + page_shift = PAGE_SHIFT; > > - for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) { > - int err; > - > - 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, > + min(page_shift, PMD_SHIFT)); We can easily extend to PUD huge mappings right? Not sure whether we should keep everything symmetric to how vmap_range_noflush() operates right now, since P4D mappings don't exist, but PUD looks worthwhile. > } > > int vmap_pages_range_noflush(unsigned long addr, unsigned long end,