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Tue, 14 May 2019 09:27:33 +0000 (UTC) To: Christian Borntraeger , Cornelia Huck References: <1556749903-19221-1-git-send-email-walling@linux.ibm.com> <09293a1c-d000-83a8-46b8-b97ad4fa9774@de.ibm.com> <56e3ace1-6e48-0e20-47d5-b07ac6dfcf31@redhat.com> <20190513134637.3d8bb275.cohuck@redhat.com> <898144e3-615e-5074-fb68-bf9995c64609@de.ibm.com> <155d2ca3-6a48-c99a-fe42-dca8e3fd4344@redhat.com> <066c7470-94a3-a922-9a12-1ca42e474c51@de.ibm.com> <20190514104934.6bba9232.cohuck@redhat.com> <47f7134b-338f-0207-88ae-4c1969be3786@redhat.com> <13b0f0b2-f7c7-01fb-0e17-92bd47d9c346@de.ibm.com> <00b5d031-227b-38f7-9512-e36c3b655c62@de.ibm.com> <27bd36e1-a102-e793-6a61-3e7acb6f1255@de.ibm.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: <078b7bcd-de03-743d-a150-456be0b09362@redhat.com> Date: Tue, 14 May 2019 11:27:32 +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: <27bd36e1-a102-e793-6a61-3e7acb6f1255@de.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Tue, 14 May 2019 09:27:37 +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] [qemu-s390x] [PATCH v4] s390: diagnose 318 info reset and migration support 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: Collin Walling , mst@redhat.com, qemu-devel@nongnu.org, pasic@linux.ibm.com, qemu-s390x@nongnu.org, pbonzini@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 14.05.19 11:25, Christian Borntraeger wrote: > > > On 14.05.19 11:23, Christian Borntraeger wrote: >> >> >> On 14.05.19 11:20, David Hildenbrand wrote: >>> On 14.05.19 11:10, Christian Borntraeger wrote: >>>> >>>> >>>> On 14.05.19 10:59, David Hildenbrand wrote: >>>>> On 14.05.19 10:49, Cornelia Huck wrote: >>>>>> On Tue, 14 May 2019 10:37:32 +0200 >>>>>> Christian Borntraeger wrote: >>>>>> >>>>>>> On 14.05.19 09:28, David Hildenbrand wrote: >>>>>>>>>>> But that can be tested using the runability information if I am not wrong. >>>>>>>>>> >>>>>>>>>> You mean the cpu level information, right? >>>>>>>> >>>>>>>> Yes, query-cpu-definition includes for each model runability information >>>>>>>> via "unavailable-features" (valid under the started QEMU machine). >>>>>>>> >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>> and others that we have today. >>>>>>>>>>>> >>>>>>>>>>>> So yes, I think this would be acceptable. >>>>>>>>>>> >>>>>>>>>>> I guess it is acceptable yes. I doubt anybody uses that many CPUs in >>>>>>>>>>> production either way. But you never know. >>>>>>>>>> >>>>>>>>>> I think that using that many cpus is a more uncommon setup, but I still >>>>>>>>>> think that having to wait for actual failure >>>>>>>>> >>>>>>>>> That can happen all the time today. You can easily say z14 in the xml when >>>>>>>>> on a zEC12. Only at startup you get the error. The question is really: >>>>>>>> >>>>>>>> "-smp 248 -cpu host" will no longer work, while e.g. "-smp 248 -cpu z12" >>>>>>>> will work. Actually, even "-smp 248" will no longer work on affected >>>>>>>> machines. >>>>>>>> >>>>>>>> That is why wonder if it is better to disable the feature and print a >>>>>>>> warning. Similar to CMMA, where want want to tolerate when CMMA is not >>>>>>>> possible in the current environment (huge pages). >>>>>>>> >>>>>>>> "Diag318 will not be enabled because it is not compatible with more than >>>>>>>> 240 CPUs". >>>>>>>> >>>>>>>> However, I still think that implementing support for more than one SCLP >>>>>>>> response page is the best solution. Guests will need adaptions for > 240 >>>>>>>> CPUs with Diag318, but who cares? Existing setups will continue to work. >>>>>>>> >>>>>>>> Implementing that SCLP thingy will avoid any warnings and any errors. It >>>>>>>> just works from the QEMU perspective. >>>>>>>> >>>>>>>> Is implementing this realistic? >>>>>>> >>>>>>> Yes it is but it will take time. I will try to get this rolling. To make >>>>>>> progress on the diag318 thing, can we error on startup now and simply >>>>>>> remove that check when when have implemented a larger sccb? If we would >>>>>>> now do all kinds of "change the max number games" would be harder to "fix". >>>>>> >>>>>> So, the idea right now is: >>>>>> >>>>>> - fail to start if you try to specify a diag318 device and more than >>>>>> 240 cpus (do we need a knob to turn off the device?) >>>>>> - in the future, support more than one SCLP response page >>>>>> >>>>>> I'm getting a bit lost in the discussion; but the above sounds >>>>>> reasonable to me. >>>>>> >>>>> >>>>> We can >>>>> >>>>> 1. Fail to start with #cpus > 240 when diag318=on >>>>> 2. Remove the error once we support more than one SCLP response page >>>>> >>>>> Or >>>>> >>>>> 1. Allow to start with #cpus > 240 when diag318=on, but indicate only >>>>> 240 CPUs via SCLP >>>>> 2. Print a warning >>>>> 3. Remove the restriction and the warning once we support more than one >>>>> SCLP response page >>>>> >>>>> While I prefer the second approach (similar to defining zPCI devices >>>>> without zpci=on), I could also live with the first approach. >>>> >>>> I prefer approach 1. >>>> >>> >>> Isn't approach #2 what we discussed (limiting sclp, but of course to 247 >>> CPUs), but with an additional warning? I'm confused. >> >> Different numbering interpretion. I was talking about 1 = "Allow to start with #cpus > 240 when diag318=on, but indicate only >> 240 CPUs via SCLP" > > So yes, variant 2 when I use your numbering. The only question is: do we need > a warning? It probably does not hurt. After all, we are talking about 1 VCPU that the guest can only use by indirect probing ... I leave that up to Collin :) -- Thanks, David / dhildenb