From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E26371C688 for ; Wed, 3 Jan 2024 17:43:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="gFnvLmzd" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-5e763e03f4dso109994767b3.2 for ; Wed, 03 Jan 2024 09:43:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1704303827; x=1704908627; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:reply-to:from:to:cc :subject:date:message-id:reply-to; bh=5ch7NvB2LWYlTvgGgKo2EIdYp2sGxx+1NC8FOV8MBa8=; b=gFnvLmzdI/s0DG37lEgq/rJbZiLYdRe5ELXdvUTfk22YE8/RHE+xwK02kVA5qokYbn SHQGUAyLf85+LxfNLqz8vXYUR+GJN+de2HhTfAah7bR5EHbmZbnxQyuaPI52l/5sr+dw 4JK1CL7lXgdhjg36eELpI5uWwo35rjWaNLQ2JUSA2XJo1oGfE+sMytrd/3IPpgqbqnaM WPcJADzCHMO80YTwDuJg4LyElf8+agsFWl06VANnHkG1mLmQoI1lSwc/sL3Z9lJUkHEP KyQ9ay/QoSgvUepno006TOnY6H7PKyDA5ZWuzsZ/6MxS7UIPTAdOxfXI4cSMjtStdlyJ tNpg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704303827; x=1704908627; h=cc:to:from:subject:message-id:mime-version:date:reply-to :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=5ch7NvB2LWYlTvgGgKo2EIdYp2sGxx+1NC8FOV8MBa8=; b=BmtOhogfWYYKc5/99TF3CFZ9TUfsThZObLbDxlXXcuAYTrE17Iw0Pnfb99PNfuJpzO m3j47U9hwAAKxTO9wiJ6bD0C82P5NPw+gBDQoHeEh1b9yvj1CilUx05mndRi3DT1/6zi uFuTsswnOS7S6CXZ7afwBqGDPIxQBeSrwkstA0h9ggJwbuODne3U5K0JTcyxRM8wDh44 gweKva/UShHTX8rvmSJZbTads9FziUkRHm3WvTf+h1DTu8VUhULErpNcdkSq2cte5nNs 0SNu3Q5m7Z2ac3G5BKE0rOkYkihtjN4vA7fgkzuOLiTFl5FAb4FbaTYAzVI2KE7rGr/g Yw1g== X-Gm-Message-State: AOJu0YzQyjGGV7UR+q9WkkmypJY5SbT+PC4CBNHS/BsffmRnpHYJek0i O1I4RAdfe1qtKvwMoVKRd8YY/CteLvnP4QLCcw== X-Google-Smtp-Source: AGHT+IFVYbxeck6qY0stZ+gHuJMU9yrJ7fDaUy0TVY05Bz/4NTgmYhY/zjYlworFaWfsAuVE1XItsh0J6YQ= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:690c:a9d:b0:5e8:f747:1cb3 with SMTP id ci29-20020a05690c0a9d00b005e8f7471cb3mr7073043ywb.1.1704303826874; Wed, 03 Jan 2024 09:43:46 -0800 (PST) Reply-To: Sean Christopherson Date: Wed, 3 Jan 2024 09:43:43 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20240103174343.3016720-1-seanjc@google.com> Subject: [ANNOUNCE] PUCK Notes - 2024.01.03 - Post-copy for guest_memfd() From: Sean Christopherson To: Sean Christopherson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Paolo Bonzini , James Houghton , Peter Xu , Axel Rasmussen , Oliver Upton , David Matlack , Aaron Lewis , Isaku Yamahata , Yan Zhao , Marc Zyngier Content-Type: text/plain; charset="UTF-8" Recording and slides of the post-copy for guest_memfd discussion: https://drive.google.com/corp/drive/folders/1_3bLYrR7oYZ06XvOPY_xZGUApGhq-j3W?resourcekey=0-0C1BYqhodcNvHFIqVwKMTg Key takeaways: - There is no known use case for tying "data invalid" to the guest_memfd inode, i.e. letting each "view" (struct file / struct kvm / VM) control its own behavior is acceptable, and arguably desirable as it provides userspace more flexibility. - If the "data invalid" attribute is tied to a given view, then routing the ioctl() through KVM provides a superset of functionality compared to making a guest_memfd specific ioctl(), e.g. KVM can apply the attribute to any gfn regardless of backing store. - Pursuing a fully generic file-based solution is undesirable as there are a large number of questions that need answers, and there is no known use case beyond KVM to drive those discussions. Feel free to chime in with anything important that I missed.