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=1794595919; b=wwT44mCmJAXujwHOBTwoySBWXm59QPo2XSLnuUta0aPTR6cAciX8kGIAvQPKZXaYG5hb 23vocNa3ZwghGlmoZ3XeM4B9A93Bcr03ZeQbV+JJRUkxh7LGhc+hMusz6kUm3S2/C+IP3 vDmvPFv2xJMr8E72/vdxjFYyC2tRtLl1wdSa5lkdWuJdlqDPm7u1CxmCzvdYMK7AHFJ9C BC71Jvh8hfxEexktnZoxx3nZKy4ngkO9tmDpD9kS0FsFWtPpZGwA5U1CvkJdPpgQTQS5R Qg5yCNZi+XG9WyWr8EzWphVGgCy6FCyMecaNQ7fx8o/GFuB/Qd8qFVn295VZmmdp64A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794595919; 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=5muRXWS1rFjtRwmxUHcdPdK+9QBRwjjtk/I3ke8eqss=; b=v+atrSPL295N4ACiyTOZlPvhatfk6lRidnFbe2yD7c8jGM+TPnFe0KCu4tvKy2Rn1nAF rLp79Ttkpgjj1RTMidHxlPsuFfmomifgBL/mA0nStASLdURjfSS7lCgBfcmiXfL3DCok6 lFbP90DmJpQj9O257/NQoHx6UzdJi+8kquSFUGK1unAn58Nv4mFSeFfP18Y75DQB46TnV MWGMA9lL65KHBkI+S6yjmbIaofwnekU29uqMros0MCopX8JVGfOFeBst/RG/D4hIW+omc RV5YSyShiKp72Vd6tr2vjEuSBiDMvC0ANtuHGuA1/sDP8qfmH+G1bhOa7L1fMT4ygOQ== 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=XzAFPkN7; 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 26038606A323; Fri, 13 Nov 2026 18:51:58 +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=XzAFPkN7 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 91B0F1F000C4; Fri, 13 Nov 2026 18:51:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794595918; bh=5muRXWS1rFjtRwmxUHcdPdK+9QBRwjjtk/I3ke8eqss=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=XzAFPkN7MUXlKgAkmPOQRLSCSAt2PwqC0Kcv+HnyUqadeayf26mt5dOB87zAhmnsL rCM/LOn1v4X8mo04YABi6kewxSg+rOZSdDxrb5UOebeOVDzcvlJzot+uNTf8h7Ixtr dhn82CAc62qemGvmxq0ChSKEdR1156L63Gfde8CamKm69f2i7gWALhNCtLos241caU SMUSWuXj2DhPLnm+iDL0xVjmBG9PQVccC5ep41dBb7XuYBjXOcqMPAR+VbhxURTeMW Ivqjv+vG9iPHvq9/l7fzKDH3I7PS44kkVRvz88GIIpeGHqch7+hqspqTFss6NGgs+4 90lFUZKzvLglA== Message-ID: <3314e44d-dbfe-45da-a1b0-8337784a5e86@kernel.org> Date: Fri, 13 Nov 2026 19:51:49 +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 v3 5/9] mm/mprotect: add MM_CP_PERM_UPGRADE To: =?UTF-8?Q?Carlos_L=C3=B3pez?= , kvm@vger.kernel.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux-riscv@lists.infradead.org, seanjc@google.com, pbonzini@redhat.com, akpm@linux-foundation.org, peterx@redhat.com, ljs@kernel.org, imbrenda@linux.ibm.com, borntraeger@linux.ibm.com, frankja@linux.ibm.com, "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato References: <20261112142039.907090-2-clopez@suse.de> <20261112142039.907090-7-clopez@suse.de> 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: <20261112142039.907090-7-clopez@suse.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 11/12/26 15:20, Carlos López wrote: > Add a change_protection() flag for changes that only add permissions, > so that MMU notifier users can keep their mappings and fault in the new > permissions later. mprotect() sets it when the new VMA flags only add > read, write or execute permissions, or VM_ACCOUNT, which does not affect > the page tables. Any other change, such as a different protection key, > is not an upgrade. > > Signed-off-by: Carlos López > --- > include/linux/mm.h | 2 ++ > mm/mprotect.c | 13 +++++++++++++ > 2 files changed, 15 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 6af3b7008f1a..001829a61405 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3585,6 +3585,8 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen); > #define MM_CP_UFFD_RWP_RESOLVE (1UL << 5) /* resolve rwp */ > #define MM_CP_UFFD_RWP_ALL (MM_CP_UFFD_RWP | \ > MM_CP_UFFD_RWP_RESOLVE) > +/* Whether this change only upgrades/adds permissions */ > +#define MM_CP_PERM_UPGRADE (1UL << 6) > > bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, > pte_t pte); > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 84bcfe0281d3..8c0fcd10f5a3 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -767,6 +767,17 @@ static const struct mm_walk_ops prot_none_walk_ops = { > .walk_lock = PGWALK_WRLOCK, > }; > > +static bool vma_flags_is_perm_upgrade(vma_flags_t old_vma_flags, > + vma_flags_t new_vma_flags) Two tab indent. > +{ > + vm_flags_t old = vma_flags_to_legacy(old_vma_flags); > + vm_flags_t new = vma_flags_to_legacy(new_vma_flags); > + /* VM_ACCOUNT does not affect page tables */ > + vm_flags_t mask = VM_READ | VM_WRITE | VM_EXEC | VM_ACCOUNT; Why is VM_ACCOUNT a permission upgrade? At best it's "no change". What am I missing? Also, what you really care about is "no permission downgrade", and "no permission upgrade" is not the inverse of that ;) -- Cheers, David