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[109.43.177.190]) by smtp.gmail.com with ESMTPSA id n8-20020a05600c4f8800b003cfd64b6be1sm6445455wmq.27.2022.11.24.02.46.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Nov 2022 02:46:40 -0800 (PST) Message-ID: Date: Thu, 24 Nov 2022 11:46:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.13.0 Subject: Re: [PATCH] KVM: s390: vsie: Fix the initialization of the epoch extension (epdx) field Content-Language: en-US To: Janosch Frank , kvm@vger.kernel.org, Claudio Imbrenda Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Christian Borntraeger , David Hildenbrand , "Collin L. Walling" , Jason J Herne References: <20221123090833.292938-1-thuth@redhat.com> <4d46020f-f33a-474c-b791-be11c2ce2aa6@linux.ibm.com> From: Thomas Huth In-Reply-To: <4d46020f-f33a-474c-b791-be11c2ce2aa6@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/11/2022 11.27, Janosch Frank wrote: > On 11/23/22 10:08, Thomas Huth wrote: >> We recently experienced some weird huge time jumps in nested guests when >> rebooting them in certain cases. After adding some debug code to the epoch >> handling in vsie.c (thanks to David Hildenbrand for the idea!), it was >> obvious that the "epdx" field (the multi-epoch extension) did not get set >> to 0xff in case the "epoch" field was negative. >> Seems like the code misses to copy the value from the epdx field from >> the guest to the shadow control block. By doing so, the weird time >> jumps are gone in our scenarios. >> >> Link: https://bugzilla.redhat.com/show_bug.cgi?id=2140899 >> Fixes: 8fa1696ea781 ("KVM: s390: Multiple Epoch Facility support") >> Signed-off-by: Thomas Huth > > Could you please add a test for this to the KVM unit tests? > I'd guess you might already have some code for it from your debugging sessions. I don't have some test code for this yet - I was only testing with the scenario that is described in the bugzilla ticket. But sure, I can have a try to come up with a k-u-t test. Thomas