From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85C82C433DF for ; Fri, 15 May 2020 14:55:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5CB3D2076A for ; Fri, 15 May 2020 14:55:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UNNMf+6M" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726188AbgEOOzP (ORCPT ); Fri, 15 May 2020 10:55:15 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:33931 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726140AbgEOOzP (ORCPT ); Fri, 15 May 2020 10:55:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589554512; 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=x2C1LTXgRodL7MD8BAdmR4DJ7nYvn5rUoJyzNq68mBw=; b=UNNMf+6MHHFK+5m/ZEgq2U67BQBA01AmJkABMhinZ19MhNXyvfIiJX5JddivvvqaZaP8Fa VgEY9Gl2gew+ec1QAlFjtXU3b0t475AgR660gwnVqUZLD3ZUIoeodCa/ebIwhorzdReQNG nVmeiMT28A3yvei25lb31O/y6C70NJQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-101-kt-1HhUqOHyBMCgfx-YdpQ-1; Fri, 15 May 2020 10:55:10 -0400 X-MC-Unique: kt-1HhUqOHyBMCgfx-YdpQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 571BAC7441; Fri, 15 May 2020 14:55:09 +0000 (UTC) Received: from [10.36.114.77] (ovpn-114-77.ams2.redhat.com [10.36.114.77]) by smtp.corp.redhat.com (Postfix) with ESMTP id A37EE6E9F0; Fri, 15 May 2020 14:54:47 +0000 (UTC) Subject: Re: [PATCH v1 01/17] exec: Introduce ram_block_discard_set_(unreliable|required)() To: qemu-devel@nongnu.org Cc: kvm@vger.kernel.org, qemu-s390x@nongnu.org, Richard Henderson , Paolo Bonzini , "Dr . David Alan Gilbert" , Eduardo Habkost , "Michael S . Tsirkin" References: <20200506094948.76388-1-david@redhat.com> <20200506094948.76388-2-david@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <8dc6cefb-63ee-9310-ce18-abf558a08b39@redhat.com> Date: Fri, 15 May 2020 16:54:46 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200506094948.76388-2-david@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 06.05.20 11:49, David Hildenbrand wrote: > We want to replace qemu_balloon_inhibit() by something more generic. > Especially, we want to make sure that technologies that really rely on > RAM block discards to work reliably to run mutual exclusive with > technologies that break it. > > E.g., vfio will usually pin all guest memory, turning the virtio-balloon > basically useless and make the VM consume more memory than reported via > the balloon. While the balloon is special already (=> no guarantees, same > behavior possible afer reboots and with huge pages), this will be > different, especially, with virtio-mem. > > Let's implement a way such that we can make both types of technology run > mutually exclusive. We'll convert existing balloon inhibitors in successive > patches and add some new ones. Add the check to > qemu_balloon_is_inhibited() for now. We might want to make > virtio-balloon an acutal inhibitor in the future - however, that > requires more thought to not break existing setups. > > Cc: "Michael S. Tsirkin" > Cc: Richard Henderson > Cc: Paolo Bonzini > Signed-off-by: David Hildenbrand > --- > balloon.c | 3 ++- > exec.c | 48 +++++++++++++++++++++++++++++++++++++++++++ > include/exec/memory.h | 41 ++++++++++++++++++++++++++++++++++++ > 3 files changed, 91 insertions(+), 1 deletion(-) > > diff --git a/balloon.c b/balloon.c > index f104b42961..c49f57c27b 100644 > --- a/balloon.c > +++ b/balloon.c > @@ -40,7 +40,8 @@ static int balloon_inhibit_count; > > bool qemu_balloon_is_inhibited(void) > { > - return atomic_read(&balloon_inhibit_count) > 0; > + return atomic_read(&balloon_inhibit_count) > 0 || > + ram_block_discard_is_broken(); > } > > void qemu_balloon_inhibit(bool state) > diff --git a/exec.c b/exec.c > index 2874bb5088..52a6e40e99 100644 > --- a/exec.c > +++ b/exec.c > @@ -4049,4 +4049,52 @@ void mtree_print_dispatch(AddressSpaceDispatch *d, MemoryRegion *root) > } > } > > +static int ram_block_discard_broken; > + > +int ram_block_discard_set_broken(bool state) > +{ > + int old; > + > + if (!state) { > + atomic_dec(&ram_block_discard_broken); > + return 0; > + } > + > + do { > + old = atomic_read(&ram_block_discard_broken); > + if (old < 0) { > + return -EBUSY; > + } > + } while (atomic_cmpxchg(&ram_block_discard_broken, old, old + 1) != old); > + return 0; > +} > + > +int ram_block_discard_set_required(bool state) > +{ > + int old; > + > + if (!state) { > + atomic_inc(&ram_block_discard_broken); > + return 0; > + } > + > + do { > + old = atomic_read(&ram_block_discard_broken); > + if (old > 0) { > + return -EBUSY; > + } > + } while (atomic_cmpxchg(&ram_block_discard_broken, old, old - 1) != old); > + return 0; > +} > + > +bool ram_block_discard_is_broken(void) > +{ > + return atomic_read(&ram_block_discard_broken) > 0; > +} > + > +bool ram_block_discard_is_required(void) > +{ > + return atomic_read(&ram_block_discard_broken) < 0; > +} > + > #endif > diff --git a/include/exec/memory.h b/include/exec/memory.h > index e000bd2f97..9bb5ced38d 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -2463,6 +2463,47 @@ static inline MemOp devend_memop(enum device_endian end) > } > #endif > > +/* > + * Inhibit technologies that rely on discarding of parts of RAM blocks to work > + * reliably, e.g., to manage the actual amount of memory consumed by the VM > + * (then, the memory provided by RAM blocks might be bigger than the desired > + * memory consumption). This *must* be set if: > + * - Discarding parts of a RAM blocks does not result in the change being > + * reflected in the VM and the pages getting freed. > + * - All memory in RAM blocks is pinned or duplicated, invaldiating any previous > + * discards blindly. > + * - Discarding parts of a RAM blocks will result in integrity issues (e.g., > + * encrypted VMs). > + * Technologies that only temporarily pin the current working set of a > + * driver are fine, because we don't expect such pages to be discarded > + * (esp. based on guest action like balloon inflation). > + * > + * This is *not* to be used to protect from concurrent discards (esp., > + * postcopy). > + * > + * Returns 0 if successful. Returns -EBUSY if a technology that relies on > + * discards to work reliably is active. > + */ > +int ram_block_discard_set_broken(bool state); > + > +/* > + * Inhibit technologies that will break discarding of pages in RAM blocks. > + * > + * Returns 0 if successful. Returns -EBUSY if discards are already set to > + * broken. > + */ > +int ram_block_discard_set_required(bool state); > + > +/* > + * Test if discarding of memory in ram blocks is broken. > + */ > +bool ram_block_discard_is_broken(void); > + > +/* > + * Test if discarding of memory in ram blocks is required to work reliably. > + */ > +bool ram_block_discard_is_required(void); > + > #endif > > #endif > I'm wondering if I'll just call these functions ram_block_discard_disable() and ram_block_discard_require() -- Thanks, David / dhildenb From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 111F0C433E0 for ; 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Fri, 15 May 2020 10:55:10 -0400 X-MC-Unique: kt-1HhUqOHyBMCgfx-YdpQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 571BAC7441; Fri, 15 May 2020 14:55:09 +0000 (UTC) Received: from [10.36.114.77] (ovpn-114-77.ams2.redhat.com [10.36.114.77]) by smtp.corp.redhat.com (Postfix) with ESMTP id A37EE6E9F0; Fri, 15 May 2020 14:54:47 +0000 (UTC) Subject: Re: [PATCH v1 01/17] exec: Introduce ram_block_discard_set_(unreliable|required)() To: qemu-devel@nongnu.org References: <20200506094948.76388-1-david@redhat.com> <20200506094948.76388-2-david@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <8dc6cefb-63ee-9310-ce18-abf558a08b39@redhat.com> Date: Fri, 15 May 2020 16:54:46 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200506094948.76388-2-david@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Received-SPF: pass client-ip=207.211.31.120; envelope-from=david@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/14 22:56:02 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Habkost , kvm@vger.kernel.org, "Michael S . Tsirkin" , "Dr . David Alan Gilbert" , qemu-s390x@nongnu.org, Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 06.05.20 11:49, David Hildenbrand wrote: > We want to replace qemu_balloon_inhibit() by something more generic. > Especially, we want to make sure that technologies that really rely on > RAM block discards to work reliably to run mutual exclusive with > technologies that break it. > > E.g., vfio will usually pin all guest memory, turning the virtio-balloon > basically useless and make the VM consume more memory than reported via > the balloon. While the balloon is special already (=> no guarantees, same > behavior possible afer reboots and with huge pages), this will be > different, especially, with virtio-mem. > > Let's implement a way such that we can make both types of technology run > mutually exclusive. We'll convert existing balloon inhibitors in successive > patches and add some new ones. Add the check to > qemu_balloon_is_inhibited() for now. We might want to make > virtio-balloon an acutal inhibitor in the future - however, that > requires more thought to not break existing setups. > > Cc: "Michael S. Tsirkin" > Cc: Richard Henderson > Cc: Paolo Bonzini > Signed-off-by: David Hildenbrand > --- > balloon.c | 3 ++- > exec.c | 48 +++++++++++++++++++++++++++++++++++++++++++ > include/exec/memory.h | 41 ++++++++++++++++++++++++++++++++++++ > 3 files changed, 91 insertions(+), 1 deletion(-) > > diff --git a/balloon.c b/balloon.c > index f104b42961..c49f57c27b 100644 > --- a/balloon.c > +++ b/balloon.c > @@ -40,7 +40,8 @@ static int balloon_inhibit_count; > > bool qemu_balloon_is_inhibited(void) > { > - return atomic_read(&balloon_inhibit_count) > 0; > + return atomic_read(&balloon_inhibit_count) > 0 || > + ram_block_discard_is_broken(); > } > > void qemu_balloon_inhibit(bool state) > diff --git a/exec.c b/exec.c > index 2874bb5088..52a6e40e99 100644 > --- a/exec.c > +++ b/exec.c > @@ -4049,4 +4049,52 @@ void mtree_print_dispatch(AddressSpaceDispatch *d, MemoryRegion *root) > } > } > > +static int ram_block_discard_broken; > + > +int ram_block_discard_set_broken(bool state) > +{ > + int old; > + > + if (!state) { > + atomic_dec(&ram_block_discard_broken); > + return 0; > + } > + > + do { > + old = atomic_read(&ram_block_discard_broken); > + if (old < 0) { > + return -EBUSY; > + } > + } while (atomic_cmpxchg(&ram_block_discard_broken, old, old + 1) != old); > + return 0; > +} > + > +int ram_block_discard_set_required(bool state) > +{ > + int old; > + > + if (!state) { > + atomic_inc(&ram_block_discard_broken); > + return 0; > + } > + > + do { > + old = atomic_read(&ram_block_discard_broken); > + if (old > 0) { > + return -EBUSY; > + } > + } while (atomic_cmpxchg(&ram_block_discard_broken, old, old - 1) != old); > + return 0; > +} > + > +bool ram_block_discard_is_broken(void) > +{ > + return atomic_read(&ram_block_discard_broken) > 0; > +} > + > +bool ram_block_discard_is_required(void) > +{ > + return atomic_read(&ram_block_discard_broken) < 0; > +} > + > #endif > diff --git a/include/exec/memory.h b/include/exec/memory.h > index e000bd2f97..9bb5ced38d 100644 > --- a/include/exec/memory.h > +++ b/include/exec/memory.h > @@ -2463,6 +2463,47 @@ static inline MemOp devend_memop(enum device_endian end) > } > #endif > > +/* > + * Inhibit technologies that rely on discarding of parts of RAM blocks to work > + * reliably, e.g., to manage the actual amount of memory consumed by the VM > + * (then, the memory provided by RAM blocks might be bigger than the desired > + * memory consumption). This *must* be set if: > + * - Discarding parts of a RAM blocks does not result in the change being > + * reflected in the VM and the pages getting freed. > + * - All memory in RAM blocks is pinned or duplicated, invaldiating any previous > + * discards blindly. > + * - Discarding parts of a RAM blocks will result in integrity issues (e.g., > + * encrypted VMs). > + * Technologies that only temporarily pin the current working set of a > + * driver are fine, because we don't expect such pages to be discarded > + * (esp. based on guest action like balloon inflation). > + * > + * This is *not* to be used to protect from concurrent discards (esp., > + * postcopy). > + * > + * Returns 0 if successful. Returns -EBUSY if a technology that relies on > + * discards to work reliably is active. > + */ > +int ram_block_discard_set_broken(bool state); > + > +/* > + * Inhibit technologies that will break discarding of pages in RAM blocks. > + * > + * Returns 0 if successful. Returns -EBUSY if discards are already set to > + * broken. > + */ > +int ram_block_discard_set_required(bool state); > + > +/* > + * Test if discarding of memory in ram blocks is broken. > + */ > +bool ram_block_discard_is_broken(void); > + > +/* > + * Test if discarding of memory in ram blocks is required to work reliably. > + */ > +bool ram_block_discard_is_required(void); > + > #endif > > #endif > I'm wondering if I'll just call these functions ram_block_discard_disable() and ram_block_discard_require() -- Thanks, David / dhildenb