From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794582407; b=0aqszF5ZJeqjsaVzbS78bO9DFfhOmRwXLvbDVS5ZKDJhp+AYy/GFxWMx731ikHmQwN4L XuffsYQis/YVvdqHSecV++5O5deUFVN0vOmm3xMGzKLCFCECjW7qOJPglYS8QWf6xzDMK KR5b2xXZL3+lZ/VwZETTmfPqklWrjeuF9sXIaV4SLH32XGN+aAPjp0IC9Ds/DbLrc/kzV xn1FSQ57qFbPWdaQZljOIyig4OJAQGIgtiwYGIIXmc2H+K20zr/3fJtNkSf38pYgVD1QW DnCGoxNsuuz3/3J+M7amijN9IaQ+VF9AFD94uN+QyX2kH12wyYa43l/3BW+FK4PnMWw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794582407; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=D8CAID1ghut0Mz9KCvy4wmmXQMXhDupoD4LdqfioSZU=; b=ab7f8CRkMDAmkBLifwBolKPJSXfhMm15aOy1DyikVlVjzigy0fwMVxT/55Vr7xVQgOmZ VlaMNV9Fbxn/jcCTokmQOJN2MiEDEPY4H3mItKcQf3FSpFX8F5WYASs2zz5o9D5/GJv2L +yCnsoJbVkxid2AAiEAvlzoJN7qwIwm7gbOKjn/R8EnqknSPzPrJ6q6dWuMMgK1A6tkE9 cQZSCkBHM8d6Dip1JiSperOH7EY2w5MO1ohTllOeAQdjdPTs6yIT1/mm4uro7UMfF2Uh+ P9ZoBQPVqXj7jgefFeH3EY6jM+efYHqvDychWajCqfycs7w0CWMlLbXFXqM+m+Ui1Yg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=H2qrb7Rp; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0973606EB45 for ; Fri, 13 Nov 2026 15:06:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=H2qrb7Rp Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3CDF51F000C4; Fri, 13 Nov 2026 15:06:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794582407; bh=D8CAID1ghut0Mz9KCvy4wmmXQMXhDupoD4LdqfioSZU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=H2qrb7Rpd2r+cC4CaEtlaiTSlfIPhvlmkvqkSxsrfLBKEv87ZIbv5camVEplogWCH 4C1Fkwjrzi5iHrDnQ/ipXSSy4npS9M/dyFiKIAZhVZU93LufHbQWL4qYfY/NrcMwA2 HNhexJwbr5tR2/BY34bADOnB6Fxh5jUFZRIdW5uokP1/cXyBLOshfN1EGY+iYqBxeA 8UwsUQLbH9D84lSPYVny9RBnMaoiK1WOsIpbro6uhE0cRvxBkqmt8DXAJhWzTtSGHk 150BUC6aY0tAE1xYfuGOqomLuK/mNQqsOv63n+N911YEQ/qLiF4gFpO3b1LjoGM+wP U6OPJu7ZDnpng== Message-ID: <0825ce63-da12-41c5-956a-039080f53571@kernel.org> Date: Fri, 13 Nov 2026 16:06:36 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/4] mm/huge_memory: use the large-page PAT encoding for huge pfn mappings To: Eliav Farber , Andrew Morton , Zi Yan Cc: Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , x86@kernel.org, William Kucharski , Vishal Moola , Alex Williamson , Matthew Wilcox , Peter Xu , "Jose A. Perez de Azpillaga" , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261112051440.16140-1-farbere@amazon.com> <20261112051440.16140-5-farbere@amazon.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20261112051440.16140-5-farbere@amazon.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/12/26 06:14, Eliav Farber wrote: > insert_pmd() and insert_pud() build the entry from the pgprot that > vmf_insert_pfn_pmd()/_pud() took from vma->vm_page_prot and passed > through pfnmap_setup_cachemode_pfn(). That pgprot carries the PTE-level > cache mode encoding, but x86 keeps the high PAT bit at bit 7 for a PTE > (_PAGE_BIT_PAT) and at bit 12 for a PMD or PUD (_PAGE_BIT_PAT_LARGE), > where bit 7 is _PAGE_PSE. > > A memtype that needs that bit, write-through or write-protect, loses it: > the cache mode index of the huge entry drops from 4-7 to 0-3. With the > PAT slots Linux programs, write-through (slot 7) becomes UC (slot 3), > and write-protect (slot 5) becomes write-combining (slot 1), which loses > the write protection. The other x86 paths that build a large entry from > a PTE pgprot convert it first, see populate_pmd() and populate_pud(). > > Convert in the two huge pfn paths. Add a generic pgprot_4k_2_large() > that returns its argument unchanged, so that only architectures which > encode the levels differently have to define it, and x86's existing > definition is picked up. > > The folio paths keep using vma->vm_page_prot as is. They map > struct-page-backed memory, which x86 maps write-back. > > Fixes: 5cad465d7fa6 ("mm: add vmf_insert_pfn_pmd()") > Signed-off-by: Eliav Farber > --- > v2: Corrected the second paragraph of the commit message. It said a > write-through range ends up write-back; with the PAT slots Linux > programs, write-through (slot 7) ends up UC (slot 3) and > write-protect (slot 5) ends up write-combining (slot 1). > Changed Fixes: from 6857be5fecae to 5cad465d7fa6 ("mm: add > vmf_insert_pfn_pmd()"), which is the commit that introduced the > unconverted pgprot. Both pointed out by Jose A. Perez de Azpillaga. > No code change. > > arch/x86/include/asm/pgtable_types.h | 2 ++ > include/linux/pgtable.h | 9 +++++++++ > mm/huge_memory.c | 4 ++-- > 3 files changed, 13 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h > index b1a669e775f4..b1ffd72e47ef 100644 > --- a/arch/x86/include/asm/pgtable_types.h > +++ b/arch/x86/include/asm/pgtable_types.h > @@ -497,6 +497,8 @@ static inline pgprotval_t protval_4k_2_large(pgprotval_t val) > return (val & ~(_PAGE_PAT | _PAGE_PAT_LARGE)) | > ((val & _PAGE_PAT) << (_PAGE_BIT_PAT_LARGE - _PAGE_BIT_PAT)); > } > + > +#define pgprot_4k_2_large pgprot_4k_2_large > static inline pgprot_t pgprot_4k_2_large(pgprot_t pgprot) > { > return __pgprot(protval_4k_2_large(pgprot_val(pgprot))); > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index 780fe849ff8b..112814d31f0c 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -1787,6 +1787,15 @@ void arch_sync_kernel_mappings(unsigned long start, unsigned long end); > #define pgprot_mhp(prot) (prot) > #endif > > +/* > + * Convert a pgprot built for a PTE so that it can be used in a PMD or PUD > + * entry. Only needed on architectures that encode attributes differently > + * between the levels; elsewhere the pgprot is used as is. > + */ > +#ifndef pgprot_4k_2_large > +#define pgprot_4k_2_large(prot) (prot) > +#endif > + > #ifdef CONFIG_MMU > #ifndef pgprot_modify > #define pgprot_modify pgprot_modify > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 052c50dadc48..945d480c1512 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1675,7 +1675,7 @@ static vm_fault_t insert_pmd(struct vm_area_struct *vma, unsigned long addr, > add_mm_counter(mm, mm_counter_file(fop.folio), HPAGE_PMD_NR); > } > } else { > - entry = pmd_mkhuge(pfn_pmd(fop.pfn, prot)); > + entry = pmd_mkhuge(pfn_pmd(fop.pfn, pgprot_4k_2_large(prot))); What on earth is 4k terminology doing in common code?! :) -- Cheers, David