From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 C9F8519DF60 for ; Thu, 19 Dec 2024 17:42:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734630136; cv=none; b=UjE0Axsyk0xXkTkcmzGnNx2AvFzj0BkkDfnM/UtmlKdqZV1CFN59K8+1SvdZ/uEkfs2iaTpjXry27WlQL6DVRyJnbYhD6q/54h6nUsJRBhIOrGcqWQiuNBfwlxZl0wC20QH0d1fI/+LkgOA4zMYnWvYIoiJFcaX1GfVwQBp+Tdw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734630136; c=relaxed/simple; bh=pqUh8/DuhjjQHnnHFyQvxUse6CQcrYTaCynWmbWhJ+M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=dJ36IQms/xClxg+gwiX9FpJKgqBRYIbGHptCNtc1PXmUZciP/F8kPnMi0NbDpltJGPffUyb9++evPN0WBE/Q1nirkwapQLNa27yXi70PzFII1g1Gj86BDcyCfkijIJU2i4UK+SGRvb+ec+fXICE9ccM4bPuIqu3i80phRppBI8w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=RqB8omv0; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RqB8omv0" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1734630133; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=eIgj5uVTAx2mGU/V5Kcpjy6tXVDbCWzbkzXU5W6plgQ=; b=RqB8omv0SlfKV0cIhxFNh7vYdTz8eF00HVaWWczITySrJS0MiMnc3qGSzbsBi04SI/PvtK k5S/DNrYrucrdwhooaYWQMCQl5pJ4RZeL6APkQiqW/yyw8JN8nujnrcWtZjbX82+QXft6B +lU5MzKN6Kaww15Srqu+l/aSYUJcqWs= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-639-H0-ePuBjNxO3xEMFM6C17Q-1; Thu, 19 Dec 2024 12:42:12 -0500 X-MC-Unique: H0-ePuBjNxO3xEMFM6C17Q-1 X-Mimecast-MFC-AGG-ID: H0-ePuBjNxO3xEMFM6C17Q Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-43610eba55bso8642295e9.3 for ; Thu, 19 Dec 2024 09:42:12 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1734630131; x=1735234931; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=eIgj5uVTAx2mGU/V5Kcpjy6tXVDbCWzbkzXU5W6plgQ=; b=Ldn9+hBCNfXRCwldS37Mj6M/YM8dIxYorUoWmNcY4XzfX7BFPygVxW8PsyU5WTenV4 tT7Hto4mt/9sV3u8HK8nByA4maq/7xUatpN87vgaqgLM+jTxTiWXAYEuz6RRASqUXvFL +qd0bdVMdWI2m4g0owiCzmcTqlwsfEZBZSRw8f4TTCwAqkiNAunC9mUJa3XyIxD7tZ6u O2h7T/GKznfckcqU7Qyj92lB2sFQErekt3nQrXwXousSvZtsb4eEB2H4yym1WnG1E4ri kdg0YsCY3cpAJkAUxLjnIKxdK+uiZiVQhfT2fJ7J+/W1D+6l9C5rKDsrbK/b+2QCKha9 Er3Q== X-Forwarded-Encrypted: i=1; AJvYcCW/wDbQlgh9K21qFvNZQIHYYTvzaGJz0u9VlwvXqxFvZKIo8X1jLM4Oqq+QYhVy8O7T4ps=@vger.kernel.org X-Gm-Message-State: AOJu0YxQxYrhSmnoq4TeX/5ZZza7vBCAhtdmJyGzcFFDO3B7q/6EHlL7 pWD+FbnCZ9EsgZuCaUWYT7wEaZZI69RvoIDbvIy1CXbf18jt0R9mbX3cz77wrRLFPOTJ63nA5us 19tF9Aa2mkiUy9VIv2N9z/7UzRKFSk1OGTVNVHBUi+GX+ZEJizQ== X-Gm-Gg: ASbGncszDyE3qRxg5x/NjAKVPmiAGtZ7O1oLt7C1o54MJJXdEJvd/vviexsCywmSQvm UNBCjTv9bQ/63HrqxMokDL8LEhUyMehgdzv/OS1mHdQar5yPQjqA7nvqIE41FTjke2IAsb8EtBu 3RSY7nG4Kju2uF/mN76tSRoLDBk9eYEonCwGSahV/ysaDcZlY60L1zDDTYmS9wXRRy5Akm5zWRY gedVRrkcQzrMXvcOFGSAkAXMg3jLw7E3SmlVK65CeJ/rB+tcMpgmA4Zo7I= X-Received: by 2002:a05:6000:704:b0:385:df2c:91b5 with SMTP id ffacd0b85a97d-38a2213d33emr10410f8f.0.1734630131105; Thu, 19 Dec 2024 09:42:11 -0800 (PST) X-Google-Smtp-Source: AGHT+IECn10GqpKtIxet4YjMA6L2x8RINhhH/WdNZXLUpqKw3Jb0XGZaNyEgRAbmfBetmHKVrfCUeA== X-Received: by 2002:a05:6000:704:b0:385:df2c:91b5 with SMTP id ffacd0b85a97d-38a2213d33emr10377f8f.0.1734630130716; Thu, 19 Dec 2024 09:42:10 -0800 (PST) Received: from [192.168.1.84] ([93.56.163.127]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-38a1c8acb85sm2008871f8f.103.2024.12.19.09.42.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Dec 2024 09:42:10 -0800 (PST) Message-ID: Date: Thu, 19 Dec 2024 18:42:09 +0100 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] KVM: x86: switch hugepage recovery thread to vhost_task To: Keith Busch Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, michael.christie@oracle.com, Tejun Heo , Luca Boccassi References: <20241108130737.126567-1-pbonzini@redhat.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/19/24 18:32, Keith Busch wrote: > This appears to be causing a user space regression. The library > "minijail" is used by virtual machine manager "crossvm". crossvm uses > minijail to fork processes, but the library requires the process be > single threaded. Prior to this patch, the process was single threaded, > but this change creates a relationship from the kvm thread to the user > process that fails minijail's test. Thanks for the report. The minijail code has a flag that's documented like this: /// Disables the check that prevents forking in a multithreaded environment. /// This is only safe if the child process calls exec immediately after /// forking. The state of locks, and whether or not they will unlock /// is undefined. Additionally, objects allocated on other threads that /// expect to be dropped when those threads cease execution will not be /// dropped. /// Thus, nothing should be called that relies on shared synchronization /// primitives referenced outside of the current thread. The safest /// way to use this is to immediately exec in the child. Is crosvm trying to do anything but exec? If not, it should probably use the flag. > Fwiw, I think the single threaded check may be misguided, but just doing > my due diligence to report the user space interaction. I don't think the check itself is misguided, but if it can be improved to only look at usermode threads somehow, that would be better. In general Linux is moving towards properly tracking the parent-child relationship of kernel processes (for vhost and io_uring, and now for KVM). Paolo