From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:36637) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hH8Y6-0005bH-Dr for qemu-devel@nongnu.org; Thu, 18 Apr 2019 11:02:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hH8Y5-0005sF-99 for qemu-devel@nongnu.org; Thu, 18 Apr 2019 11:02:02 -0400 References: <1555334842-195718-1-git-send-email-imammedo@redhat.com> <1555334842-195718-6-git-send-email-imammedo@redhat.com> <89ca3a70-066b-e40e-faaf-39a39ec976bf@de.ibm.com> <20190418113859.00248d07@redhat.com> <93d242cb-dcc4-a65d-a7c7-7232dd16a2f2@redhat.com> <20190418140116.19596c6d@redhat.com> <55880acf-9a61-9ed7-2ddd-9778b78540ee@redhat.com> <20190418165630.5a3cc493@redhat.com> From: David Hildenbrand Message-ID: <2675f1b1-fa05-ade3-9e0d-58e65e422251@redhat.com> Date: Thu, 18 Apr 2019 17:01:55 +0200 MIME-Version: 1.0 In-Reply-To: <20190418165630.5a3cc493@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v1 5/5] s390: do not call memory_region_allocate_system_memory() multiple times List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: Paolo Bonzini , qemu-devel@nongnu.org, Cornelia Huck , Halil Pasic , qemu-s390x@nongnu.org On 18.04.19 16:56, Igor Mammedov wrote: > On Thu, 18 Apr 2019 14:06:25 +0200 > David Hildenbrand wrote: > >> On 18.04.19 14:01, Igor Mammedov wrote: >>> On Thu, 18 Apr 2019 13:24:43 +0200 >>> David Hildenbrand wrote: >>> >>>> On 18.04.19 11:38, Igor Mammedov wrote: >>>>> On Tue, 16 Apr 2019 13:09:08 +0200 >>>>> Christian Borntraeger wrote: >>>>> >>>>>> This fails with more than 8TB, e.g. "-m 9T " >>>>>> >>>>>> [pid 231065] ioctl(10, KVM_SET_USER_MEMORY_REGION, {slot=0, flags=0, guest_phys_addr=0, memory_size=0, userspace_addr=0x3ffc8500000}) = 0 >>>>>> [pid 231065] ioctl(10, KVM_SET_USER_MEMORY_REGION, {slot=0, flags=0, guest_phys_addr=0, memory_size=9895604649984, userspace_addr=0x3ffc8500000}) = -1 EINVAL (Invalid argument) >>>>>> >>>>>> seems that the 2nd memslot gets the full size (and not 9TB-size of first slot). >>>>> >>>>> it turns out MemoryRegions is rendered correctly in to 2 parts (one per alias), >>>>> but follow up flatview_simplify() collapses adjacent ranges back >>>>> into big one. >>>> >>>> That sounds dangerous. Imagine doing that at runtime (e.g. hotplugging a >>>> DIMM), the kvm memory slot would temporarily be deleted to insert the >>>> new, bigger one. Guest would crash. This could happen if backing memory >>>> of two DIMMs would by pure luck be allocated side by side in user space. >>>> >>> >>> not sure I fully get your concerns, but if you look at can_merge() >>> it ensures that ranges belong to the same MemoryRegion. >>> >>> It's hard for me to say if flatview_simplify() works as designed, >>> MemoryRegion code is quite complicated so I'd deffer to Paolo's >>> opinion. >>> >> >> What I had in mind: >> >> We have the Memory Region for memory devices (m->device_memory). >> >> Assume The first DIMM is created, allocating memory in the user space >> process: >> >> [0x100000000 .. 0x20000000]. It is placed at offset 0 in m->device_memory. >> >> Guests starts to run, a second DIMM is hotplugged. Memory in user space >> process is allocated (by pure luck) at: >> >> [0x200000000 .. 0x30000000]. It is placed at offset 0x100000000 in >> m->device_memory. >> >> Without looking at the code, I could imagine that both might be merged >> into a single memory slot. That is my concern. Maybe it is not valid. > it's not. As far as I see ranges are merged only if they belong to > the same 'mr'. So to dimms will result in 2 memory sections -> 2 KVMSlots. Okay, so a shared "parent memory region" is not enough to result in a merge, only aliases. -- 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=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 03657C10F14 for ; Thu, 18 Apr 2019 15:12:24 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BF22420674 for ; Thu, 18 Apr 2019 15:12:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF22420674 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:42816 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hH8i6-0004iH-Ve for qemu-devel@archiver.kernel.org; Thu, 18 Apr 2019 11:12:22 -0400 Received: from eggs.gnu.org ([209.51.188.92]:36637) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hH8Y6-0005bH-Dr for qemu-devel@nongnu.org; Thu, 18 Apr 2019 11:02:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hH8Y5-0005sF-99 for qemu-devel@nongnu.org; Thu, 18 Apr 2019 11:02:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57080) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hH8Y4-0005r1-IH; Thu, 18 Apr 2019 11:02:00 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A5AE370D6C; Thu, 18 Apr 2019 15:01:59 +0000 (UTC) Received: from [10.36.117.52] (ovpn-117-52.ams2.redhat.com [10.36.117.52]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7482A5D960; Thu, 18 Apr 2019 15:01:56 +0000 (UTC) To: Igor Mammedov References: <1555334842-195718-1-git-send-email-imammedo@redhat.com> <1555334842-195718-6-git-send-email-imammedo@redhat.com> <89ca3a70-066b-e40e-faaf-39a39ec976bf@de.ibm.com> <20190418113859.00248d07@redhat.com> <93d242cb-dcc4-a65d-a7c7-7232dd16a2f2@redhat.com> <20190418140116.19596c6d@redhat.com> <55880acf-9a61-9ed7-2ddd-9778b78540ee@redhat.com> <20190418165630.5a3cc493@redhat.com> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwX4EEwECACgFAljj9eoCGwMFCQlmAYAGCwkI BwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEE3eEPcA/4Na5IIP/3T/FIQMxIfNzZshIq687qgG 8UbspuE/YSUDdv7r5szYTK6KPTlqN8NAcSfheywbuYD9A4ZeSBWD3/NAVUdrCaRP2IvFyELj xoMvfJccbq45BxzgEspg/bVahNbyuBpLBVjVWwRtFCUEXkyazksSv8pdTMAs9IucChvFmmq3 jJ2vlaz9lYt/lxN246fIVceckPMiUveimngvXZw21VOAhfQ+/sofXF8JCFv2mFcBDoa7eYob s0FLpmqFaeNRHAlzMWgSsP80qx5nWWEvRLdKWi533N2vC/EyunN3HcBwVrXH4hxRBMco3jvM m8VKLKao9wKj82qSivUnkPIwsAGNPdFoPbgghCQiBjBe6A75Z2xHFrzo7t1jg7nQfIyNC7ez MZBJ59sqA9EDMEJPlLNIeJmqslXPjmMFnE7Mby/+335WJYDulsRybN+W5rLT5aMvhC6x6POK z55fMNKrMASCzBJum2Fwjf/VnuGRYkhKCqqZ8gJ3OvmR50tInDV2jZ1DQgc3i550T5JDpToh dPBxZocIhzg+MBSRDXcJmHOx/7nQm3iQ6iLuwmXsRC6f5FbFefk9EjuTKcLMvBsEx+2DEx0E UnmJ4hVg7u1PQ+2Oy+Lh/opK/BDiqlQ8Pz2jiXv5xkECvr/3Sv59hlOCZMOaiLTTjtOIU7Tq 7ut6OL64oAq+zsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCghCj/CA/lc/LMthqQ773ga uB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseBfDXHA6m4B3mUTWo13nid 0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts6TZ+IrPOwT1hfB4WNC+X 2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiuQmt3yqrmN63V9wzaPhC+ xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKBTccu2AXJXWAE1Xjh6GOC 8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvFFFyAS0Nk1q/7EChPcbRb hJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh2YmnmLRTro6eZ/qYwWkC u8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRkF3TwgucpyPtcpmQtTkWS gDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0LLH63+BrrHasfJzxKXzqg rW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4vq7oFCPsOgwARAQABwsFl BBgBAgAPBQJVy5+RAhsMBQkJZgGAAAoJEE3eEPcA/4NagOsP/jPoIBb/iXVbM+fmSHOjEshl KMwEl/m5iLj3iHnHPVLBUWrXPdS7iQijJA/VLxjnFknhaS60hkUNWexDMxVVP/6lbOrs4bDZ NEWDMktAeqJaFtxackPszlcpRVkAs6Msn9tu8hlvB517pyUgvuD7ZS9gGOMmYwFQDyytpepo YApVV00P0u3AaE0Cj/o71STqGJKZxcVhPaZ+LR+UCBZOyKfEyq+ZN311VpOJZ1IvTExf+S/5 lqnciDtbO3I4Wq0ArLX1gs1q1XlXLaVaA3yVqeC8E7kOchDNinD3hJS4OX0e1gdsx/e6COvy qNg5aL5n0Kl4fcVqM0LdIhsubVs4eiNCa5XMSYpXmVi3HAuFyg9dN+x8thSwI836FoMASwOl C7tHsTjnSGufB+D7F7ZBT61BffNBBIm1KdMxcxqLUVXpBQHHlGkbwI+3Ye+nE6HmZH7IwLwV W+Ajl7oYF+jeKaH4DZFtgLYGLtZ1LDwKPjX7VAsa4Yx7S5+EBAaZGxK510MjIx6SGrZWBrrV TEvdV00F2MnQoeXKzD7O4WFbL55hhyGgfWTHwZ457iN9SgYi1JLPqWkZB0JRXIEtjd4JEQcx +8Umfre0Xt4713VxMygW0PnQt5aSQdMD58jHFxTk092mU+yIHj5LeYgvwSgZN4airXk5yRXl SE+xAvmumFBY Organization: Red Hat GmbH Message-ID: <2675f1b1-fa05-ade3-9e0d-58e65e422251@redhat.com> Date: Thu, 18 Apr 2019 17:01:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190418165630.5a3cc493@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Thu, 18 Apr 2019 15:01:59 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v1 5/5] s390: do not call memory_region_allocate_system_memory() multiple times X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Halil Pasic , Paolo Bonzini , qemu-s390x@nongnu.org, Cornelia Huck , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190418150155.lcIWmJ20YKrEfsb32s5YBEYZCMkX7Wo3SDq4yWYl1Fs@z> On 18.04.19 16:56, Igor Mammedov wrote: > On Thu, 18 Apr 2019 14:06:25 +0200 > David Hildenbrand wrote: > >> On 18.04.19 14:01, Igor Mammedov wrote: >>> On Thu, 18 Apr 2019 13:24:43 +0200 >>> David Hildenbrand wrote: >>> >>>> On 18.04.19 11:38, Igor Mammedov wrote: >>>>> On Tue, 16 Apr 2019 13:09:08 +0200 >>>>> Christian Borntraeger wrote: >>>>> >>>>>> This fails with more than 8TB, e.g. "-m 9T " >>>>>> >>>>>> [pid 231065] ioctl(10, KVM_SET_USER_MEMORY_REGION, {slot=0, flags=0, guest_phys_addr=0, memory_size=0, userspace_addr=0x3ffc8500000}) = 0 >>>>>> [pid 231065] ioctl(10, KVM_SET_USER_MEMORY_REGION, {slot=0, flags=0, guest_phys_addr=0, memory_size=9895604649984, userspace_addr=0x3ffc8500000}) = -1 EINVAL (Invalid argument) >>>>>> >>>>>> seems that the 2nd memslot gets the full size (and not 9TB-size of first slot). >>>>> >>>>> it turns out MemoryRegions is rendered correctly in to 2 parts (one per alias), >>>>> but follow up flatview_simplify() collapses adjacent ranges back >>>>> into big one. >>>> >>>> That sounds dangerous. Imagine doing that at runtime (e.g. hotplugging a >>>> DIMM), the kvm memory slot would temporarily be deleted to insert the >>>> new, bigger one. Guest would crash. This could happen if backing memory >>>> of two DIMMs would by pure luck be allocated side by side in user space. >>>> >>> >>> not sure I fully get your concerns, but if you look at can_merge() >>> it ensures that ranges belong to the same MemoryRegion. >>> >>> It's hard for me to say if flatview_simplify() works as designed, >>> MemoryRegion code is quite complicated so I'd deffer to Paolo's >>> opinion. >>> >> >> What I had in mind: >> >> We have the Memory Region for memory devices (m->device_memory). >> >> Assume The first DIMM is created, allocating memory in the user space >> process: >> >> [0x100000000 .. 0x20000000]. It is placed at offset 0 in m->device_memory. >> >> Guests starts to run, a second DIMM is hotplugged. Memory in user space >> process is allocated (by pure luck) at: >> >> [0x200000000 .. 0x30000000]. It is placed at offset 0x100000000 in >> m->device_memory. >> >> Without looking at the code, I could imagine that both might be merged >> into a single memory slot. That is my concern. Maybe it is not valid. > it's not. As far as I see ranges are merged only if they belong to > the same 'mr'. So to dimms will result in 2 memory sections -> 2 KVMSlots. Okay, so a shared "parent memory region" is not enough to result in a merge, only aliases. -- Thanks, David / dhildenb