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 7F4BE35202C; Thu, 10 Sep 2026 09:59:09 +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=1789034350; cv=none; b=se2aXF8QOaMovvWIVLv6OQLBDeSP0beHIm48QUsZM1KFcGQXxhQuOHmdh5kcEuAYyle2aMrG64gU3WV2Tc/VcVwE5VgVfL+o5GuIQkS/8C/3N6NW/iWqBULfuH0TmDV3BQpxnxS6QCwX+C/FvucYEhervK5yPRUyHd7PzHeZyl8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789034350; c=relaxed/simple; bh=fpSdg5Ex7QRSWoXO1/VxBlB62YDI7zyawiewGoJwkZ8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iYrLI48p5NQl24wOpfZxvcOi5apCTNERVQxa02kzLr+SoKSFIptrdehS8cXhFwYPedNVDQJFZ5Ybb+fBtQtPOegVTfw0cLKM2SwfzztY3Z5OQDYbDJKpSbzyThziMAv4h6gXIHi/NLaISNcGX9KfzjgJIptgUEBl5H9EiK+5Gxw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Btbp/DdQ; 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="Btbp/DdQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D81C1F000FF; Thu, 10 Sep 2026 09:58:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789034349; bh=7E7qL9hnMJksX9Fno6BkugSVMdHcPZ0KaVrs7NYY16s=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Btbp/DdQDkYguPGE72KqFMmtU62PXLGOhJ0BVA4TjekaMJ7fvAebinZO9+OCzfBGl bVNJxH1goP4pUSAi8DwHCvmb7/XxSnj55za6Aw4mxJxj0Qxf8WdK06Nvlk8ir/G2PG nv3oFP9VVn680YlbepBhluTI4FNqlR2RIac40sfu4z83Dfn7Gs5AnVNYH1AERlO8g/ O/uuq4aKITSnB3CCUCm5KnAiMgGtfX8KByqU3ga68/mWbWbRsGCbQ43yYIMZvxVY8P 6uYoKpLcmcjvXsLJkv8mBTwkXPQJo2m+p2ofMj5WVjmvyVYMna8FhMIvfDN8Tf+KW0 17DPj/qdtxCfA== Message-ID: Date: Thu, 10 Sep 2026 11:58:53 +0200 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/9] KVM: guest_memfd: take the invalidate lock when unbinding a dying file To: Shivank Garg , "Matthew Wilcox (Oracle)" , Jan Kara , Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Paolo Bonzini , Shuah Khan , Chao Peng , Nikunj A Dadhania , Michael Roth , Pankaj Gupta , Ackerley Tng , Sean Christopherson , Vishal Annapurve , Nikita Kalyazin , Patrick Roy , Pratik Sampat , Ashish Kalra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Jonathan Corbet , Shuah Khan , Peter Shier , Jim Mattson , Ricardo Koller , Ira Weiny , Fuad Tabba Cc: linux-fsdevel@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, Sashiko References: <20260805-shivank-gmem-migrate-v3-0-00d8bdec4e1d@amd.com> <20260805-shivank-gmem-migrate-v3-1-00d8bdec4e1d@amd.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: <20260805-shivank-gmem-migrate-v3-1-00d8bdec4e1d@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/5/26 08:40, Shivank Garg wrote: > kvm_gmem_unbind() skips mapping->invalidate_lock when the guest_memfd > file is already dying. All other paths that modify f->bindings hold > that lock. > > kvm_gmem_invalidate_{start,end}() checks f->bindings independently to > decide whether to begin or end KVM MMU invalidations. So, the bindings > must remain stable between the two calls. If a binding is removed in that > window, start increments mmu_invalidate_in_progress but end does not > decrement it. Example, unbind race with memory failure: > > CPU 0: memory failure CPU 1: memslot delete > ---------------------------------- --------------------------- > (guest_memfd file is dying) > kvm_gmem_error_folio() > kvm_gmem_invalidate_start() > finds binding > mmu_invalidate_in_progress++ > kvm_gmem_unbind() > get_file_active() fails > store NULL in bindings > kvm_gmem_invalidate_end() > no binding found > counter stays elevated > > mmu_invalidate_retry() then returns 1 forever, so guest page faults > retry without ever installing a mapping and the guest hangs. > > Take the invalidate lock in the dying-file path too. This prevents unbind > from removing a binding and leaking mmu_invalidate_in_progress. This is > safe because any caller that reaches this path holds slots_lock, so > kvm_gmem_release() cannot nullify the slots->gmem.file, until > kvm_gmem_unbind() finishes. > > Reported-by: Sashiko > Closes: https://lore.kernel.org/all/20260728092027.225CF1F000E9@smtp.kernel.org > Fixes: ae431059e75d ("KVM: guest_memfd: Remove bindings on memslot deletion when gmem is dying") > Signed-off-by: Shivank Garg > --- This was sent independently in the meantime, correct? (or was it included in this series, IOW what's the expected patch flow) -- Cheers, David