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 939D016C684 for ; Fri, 7 Feb 2025 09:19:59 +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=1738920001; cv=none; b=Rjqu8LCOUWmQdA5W8Q8FvK1SuuvyQIhVZNEH8fVvHruNvlFcaqOo9Jtm+fqeTOE6irrF/qZf0MKv6sd3Bm3hbtrJAH7hBFj12oPztHXERrxEM+Vs0MJhRXqBpZx85/AggGN2vPeokEhSHHFe9sCkrTsS/OgRHmxhloGIAUQqVvI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738920001; c=relaxed/simple; bh=BOSvGSnUaWn3jxNlcqKSZUu5q+UExUoJyYOA4DDgnso=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=QcoZpB8Q0m1ZokmjAymi1zQekM27WFZ7Z3lrV9rEkytZrZ9qGMl9KCEfjCxDqOyyUIcdJ/ls99xjaaFmmI82y7XFLAI/jeFNV55Ig/azddxQtLTiVDMwjzkJfnx1OhspofGVstLPykKRuSOKO8ojos7MobyNtCjusdjvP3bn8zk= 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; 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 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 ACBCB106F; Fri, 7 Feb 2025 01:20:21 -0800 (PST) Received: from [10.162.16.89] (a077893.blr.arm.com [10.162.16.89]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5AF5C3F5A1; Fri, 7 Feb 2025 01:19:53 -0800 (PST) Message-ID: Date: Fri, 7 Feb 2025 14:49:50 +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 v1 11/16] mm/vmalloc: Gracefully unmap huge ptes To: Ryan Roberts , 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> <20250205151003.88959-12-ryan.roberts@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <20250205151003.88959-12-ryan.roberts@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/5/25 20:39, Ryan Roberts wrote: > Commit f7ee1f13d606 ("mm/vmalloc: enable mapping of huge pages at pte > level in vmap") added its support by reusing the set_huge_pte_at() API, > which is otherwise only used for user mappings. But when unmapping those > huge ptes, it continued to call ptep_get_and_clear(), which is a > layering violation. To date, the only arch to implement this support is > powerpc and it all happens to work ok for it. > > But arm64's implementation of ptep_get_and_clear() can not be safely > used to clear a previous set_huge_pte_at(). So let's introduce a new > arch opt-in function, arch_vmap_pte_range_unmap_size(), which can > provide the size of a (present) pte. Then we can call > huge_ptep_get_and_clear() to tear it down properly. > > Note that if vunmap_range() is called with a range that starts in the > middle of a huge pte-mapped page, we must unmap the entire huge page so > the behaviour is consistent with pmd and pud block mappings. In this > case emit a warning just like we do for pmd/pud mappings. > > Signed-off-by: Ryan Roberts > --- > include/linux/vmalloc.h | 8 ++++++++ > mm/vmalloc.c | 18 ++++++++++++++++-- > 2 files changed, 24 insertions(+), 2 deletions(-) > > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > index 31e9ffd936e3..16dd4cba64f2 100644 > --- a/include/linux/vmalloc.h > +++ b/include/linux/vmalloc.h > @@ -113,6 +113,14 @@ static inline unsigned long arch_vmap_pte_range_map_size(unsigned long addr, uns > } > #endif > > +#ifndef arch_vmap_pte_range_unmap_size > +static inline unsigned long arch_vmap_pte_range_unmap_size(unsigned long addr, > + pte_t *ptep) > +{ > + return PAGE_SIZE; > +} > +#endif > + > #ifndef arch_vmap_pte_supported_shift > static inline int arch_vmap_pte_supported_shift(unsigned long size) > { > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index fcdf67d5177a..6111ce900ec4 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -350,12 +350,26 @@ static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > pgtbl_mod_mask *mask) > { > pte_t *pte; > + pte_t ptent; > + unsigned long size = PAGE_SIZE; Default fallback size being PAGE_SIZE like before. > > pte = pte_offset_kernel(pmd, addr); > do { > - pte_t ptent = ptep_get_and_clear(&init_mm, addr, pte); > +#ifdef CONFIG_HUGETLB_PAGE > + size = arch_vmap_pte_range_unmap_size(addr, pte); > + if (size != PAGE_SIZE) { > + if (WARN_ON(!IS_ALIGNED(addr, size))) { > + addr = ALIGN_DOWN(addr, size); > + pte = PTR_ALIGN_DOWN(pte, sizeof(*pte) * (size >> PAGE_SHIFT)); > + } > + ptent = huge_ptep_get_and_clear(&init_mm, addr, pte, size); > + if (WARN_ON(end - addr < size)) > + size = end - addr; > + } else > +#endif > + ptent = ptep_get_and_clear(&init_mm, addr, pte); ptep_get_and_clear() gets used both, when !HUGETLB_PAGE or HUGETLB_PAGE with arch_vmap_pte_range_unmap_size() returned value being PAGE_SIZE, which makes sense. > WARN_ON(!pte_none(ptent) && !pte_present(ptent)); > - } while (pte++, addr += PAGE_SIZE, addr != end); > + } while (pte += (size >> PAGE_SHIFT), addr += size, addr != end); > *mask |= PGTBL_PTE_MODIFIED; > } > LGTM Reviewed-by: Anshuman Khandual