From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B05D41930F; Fri, 5 Jun 2026 09:26:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780651600; cv=none; b=KFgLEJh9BBP9biMJrbpCYL33/LLha6LsGhFCJ8IgFy/H28tRY026PXEnwAdoTsao1V7OyhXhFkQdYW+Rk85dVO0b0Q1HCfS1tMxjUrneAOAxfNEKD5WSYidA0TFUo+U6aId36SIZgH5dLFxUNjYRXa1546Q6k3UiANBeyPjKTlw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780651600; c=relaxed/simple; bh=A502AzTmn/iFXu3GVDvOi7CYeENRSIEE2s1TZuWcVAc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=PBlT7YvwV7LWC0QIajwTYLDp5jBXootP/6uXlGe7L4OUqeogjqrf9wWPxfVE1kjSumMdo6gbNQdRxXrqhlatnza/RhauzG2i7CutK7/ljMbIgdgOCCQNK3NNpcrOJG/9Sp/dgPG7h+ANEKD4cn+1vT0g9HymY4J1euH20wz6HqU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VVZyHJO7; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VVZyHJO7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09AB71F00898; Fri, 5 Jun 2026 09:26:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780651598; bh=lsJcem04HaYvQExEBPnbV/gq8H97CMpyJrxVtD251Lg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=VVZyHJO7WkDvN4JpTQ34yrHTxsvjHVMVVEJE8F21Kb/t5T0f4e+8xhEwjX61Vp/8r eO83siNZFWz+a0MrQN1WI6TTecZ5xWLHq9E4ZQguQML73oNyESBvUHF+DrEmR70Ncg DTPQqI1+1pIS8O/j577Y2oeLWooLFduao2joDvXguGXRMw8yYUN4z5zJV1FeSR1Gql ou+tU/Rug0qjETny/E4ssGOwDXEuCK2C24zr0OjVl/M3r62wYU8MYwcEVAylrFqn3D evakRkuvwZhQ4R6qKsPnCHzwURDU/HWKY632IDJXkED4A/ElPPunV6875hMAcRTS/c 8s0kJfNLaU4QQ== Message-ID: <36d09e58-e499-4b65-b08e-6c3d9d0aa070@kernel.org> Date: Fri, 5 Jun 2026 11:26:34 +0200 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] KVM: guest_memfd: fix NUMA interleave index double-counting To: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org Cc: Sean Christopherson , Paolo Bonzini , Vlastimil Babka , Shivank Garg , kvm@vger.kernel.org References: <0eff0a90667b900bee837d06b5db5025e1f304b5.1780501924.git.mst@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: <0eff0a90667b900bee837d06b5db5025e1f304b5.1780501924.git.mst@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/3/26 17:57, Michael S. Tsirkin wrote: > kvm_gmem_get_policy() sets *ilx to the full page offset > (vm_pgoff + vma offset). But get_vma_policy() adds the page > offset on top of *ilx, so the offset is counted twice. This > causes NUMA interleaving to skip nodes: for order-0 pages the > effective index jumps by 2 for each consecutive page. > > The get_policy vm_op should return only a per-file bias in *ilx > (like shmem_get_policy does with inode->i_ino), letting > get_vma_policy() add the page-offset component. > > Fix by setting *ilx to inode->i_ino instead of the full page > offset. The page offset is computed by get_vma_policy() in > mm/mempolicy.c. The full offset is still computed > in kvm_gmem_get_policy() for mpol_shared_policy_lookup(). > shmem_get_policy() follows the same pattern. > > Found by Sashiko (sashiko.dev) AI code review. > > Fixes: ed1ffa810bd6 ("KVM: guest_memfd: Enforce NUMA mempolicy using shared policy") > Cc: Sean Christopherson > Cc: Paolo Bonzini > Assisted-by: Claude:claude-opus-4-6 > Signed-off-by: Michael S. Tsirkin > --- > virt/kvm/guest_memfd.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 69c9d6d546b2..0bcf6fc08e2d 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -438,11 +438,12 @@ static int kvm_gmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpo > } > > static struct mempolicy *kvm_gmem_get_policy(struct vm_area_struct *vma, > - unsigned long addr, pgoff_t *pgoff) > + unsigned long addr, pgoff_t *ilx) That now matches the definition in struct vm_operations_struct. > { > struct inode *inode = file_inode(vma->vm_file); > + pgoff_t pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT); > > - *pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT); > + *ilx = inode->i_ino; > > /* > * Return the memory policy for this index, or NULL if none is set. > @@ -453,7 +454,7 @@ static struct mempolicy *kvm_gmem_get_policy(struct vm_area_struct *vma, > * can then replace NULL with the default memory policy instead of the > * current task's memory policy. > */ > - return mpol_shared_policy_lookup(&GMEM_I(inode)->policy, *pgoff); > + return mpol_shared_policy_lookup(&GMEM_I(inode)->policy, pgoff); > } > #endif /* CONFIG_NUMA */ > That now matches what shmem_get_policy() does logically. Acked-by: David Hildenbrand (Arm) -- Cheers, David