From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 21DDDC55179 for ; Mon, 3 Aug 2026 12:16:41 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7A98010E5E4; Mon, 3 Aug 2026 12:16:40 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="ZhilxiHV"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id CC4BB10E5E4 for ; Mon, 3 Aug 2026 12:16:39 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 5BA2360A81; Mon, 3 Aug 2026 12:16:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0933A1F000E9; Mon, 3 Aug 2026 12:16:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785759398; bh=55xmHsjPqzaGV0ly1LUi624NBcwUFcBTGLs//q+Aif4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ZhilxiHVcGglLBMt5PIQz/4XhyzmurGW7f7hDst5wFgXLkEJ7Ql4j38SUeUjDtxpo iujYsQK51eOkQ+gMwj9rS2dVQ7eOYOVNnhbZESsOAcqCXH+mx1d/0Fdd9WEzcoiI8c vDP9WGdcT7/uIbYeu3lbftJzQrqcB1xe98RAX036DKn6XJXwFInPs1bs1Ka5WOVZcj h7OmESiRPlzjasLU3dDExgLYViNgbcUhxF4UfAyoDE9r+H+KGPx+tuBH7/2OUI0/u1 /x/TJ2Xr65rD94DLz9eth0zXRCVGm6UE64DiY5TolS1I3TuHsCYsINlPMG/kPcDX+W 4IjSrT+t9CKJg== Message-ID: Date: Mon, 3 Aug 2026 14:16:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFT 1/3] mm: export variants of vmf_insert_pfn* for use with pfn_mkwrite() To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Boris Brezillon , Thomas Zimmermann , Michal Hocko , Sergio Lopez , Christian Koenig , Huang Rui , bcm-kernel-feedback-list@broadcom.com, dri-devel@lists.freedesktop.org, linux-mm@kvack.org References: <20260731164341.1109827-1-pbonzini@redhat.com> <20260731164341.1109827-2-pbonzini@redhat.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: <20260731164341.1109827-2-pbonzini@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 7/31/26 18:43, Paolo Bonzini wrote: > Right now, users of .pfn_mkwrite() have no way to create a PTE > that has gone through maybe_mkwrite(). Because vma_set_page_prot() > will have cleared the writable PTE bit, users of fixup_user_fault() > will see a read-only PTE and have no clue that the page needs > a *second* fault to reach its final status. > > Handling this in fixup_user_fault() is problematic: the information > about the presence of *_mkwrite is only recorded in vma->vm_page_prot, > which is an opaque pgprot_t, therefore only follow_pfnmap_start() > knows how to retrieve it. > > There are actually some preexisting functions that suggest how this > is supposed to be handled, namely vmf_insert_page_mkwrite() and > vmf_insert_pfn_pmd(). Adjust mm/memory.c to export two more > functions: vmf_insert_pfn_mkwrite() for the common case where > vma->vm_page_prot is okay, and __vmf_insert_pfn_prot() when > really all parameters are needed. This makes it possible > to fix drivers that use .pfn_mkwrite together with > vmf_insert_pfn() and vmf_insert_pfn_prot(). > > Signed-off-by: Paolo Bonzini > --- > include/linux/mm.h | 4 +++ > mm/huge_memory.c | 2 +- > mm/memory.c | 75 +++++++++++++++++++++++++++++++++------------- > 3 files changed, 59 insertions(+), 22 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 34c79b5fcb9b..33c7de36b214 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4551,6 +4551,10 @@ vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr, > unsigned long pfn); > vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, > unsigned long pfn, pgprot_t pgprot); > +vm_fault_t vmf_insert_pfn_mkwrite(struct vm_area_struct *vma, unsigned long addr, > + unsigned long pfn, bool write); > +vm_fault_t __vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, > + unsigned long pfn, pgprot_t pgprot, bool mkwrite); > vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr, > unsigned long pfn); > vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma, > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index b5d1e9d4463d..2f4dcaa819b7 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1615,7 +1615,7 @@ static vm_fault_t insert_pmd(struct vm_area_struct *vma, unsigned long addr, > * @pfn: pfn to insert > * @write: whether it's a write fault > * > - * Insert a pmd size pfn. See vmf_insert_pfn() for additional info. > + * Insert a pmd size pfn. See vmf_insert_pfn_mkwrite() for additional info. > * > * Return: vm_fault_t value. > */ > diff --git a/mm/memory.c b/mm/memory.c > index 40997a26846f..7b950be8f511 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2718,6 +2718,34 @@ static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr, > return VM_FAULT_NOPAGE; > } > [...] > +vm_fault_t __vmf_insert_pfn_prot(struct vm_area_struct *vma, > + unsigned long addr, unsigned long pfn, pgprot_t pgprot, > + bool mkwrite) (We indent two tabs, I assume vmf_insert_pfn_prot uses 3 for legacy reasons after renamings) Hm, having a __ function that looks like an internal helper exported to drivers and then not adding kerneldocs. Why not simply have vmf_insert_pfn_prot_mkwrite() And add proper documentation? I guess we could also turn vmf_insert_pfn(), vmf_insert_pfn_mkwrite() and vmf_insert_pfn_prot() into simple inline functions in the header. And I'd even say that a single excessive documentation of vmf_insert_pfn_prot_mkwrite() might be sufficient, and keeping it very short for the wrappers. > +{ > + /* > + * Technically, architectures with pte_special can avoid all these > + * restrictions (same for remap_pfn_range). However we would like > + * consistency in testing and feature parity among all, so we should > + * try to keep these invariants in place for everybody. > + */ > + BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))); > + BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == > + (VM_PFNMAP|VM_MIXEDMAP)); > + BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); > + BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn)); > + > + if (addr < vma->vm_start || addr >= vma->vm_end) > + return VM_FAULT_SIGBUS; > + > + if (!pfn_modify_allowed(pfn, pgprot)) > + return VM_FAULT_SIGBUS; > + > + pfnmap_setup_cachemode_pfn(pfn, &pgprot); > + > + return insert_pfn(vma, addr, pfn, pgprot, mkwrite); > +} > +EXPORT_SYMBOL(__vmf_insert_pfn_prot); If this becomes a dedicated symbol, why not GPL? -- Cheers, David