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Thu, 19 Dec 2024 04:55:37 -0800 (PST) X-Google-Smtp-Source: AGHT+IE9Y+Dnk96cdAXS6U3t+zS4nLJrTpLDOlkmJpVPR5zTQ6oQ9kPmfgUFcE20hOS9eBN0E+banw== X-Received: by 2002:a5d:5c0c:0:b0:385:f38e:c0d3 with SMTP id ffacd0b85a97d-38a19b56d13mr2413788f8f.58.1734612937543; Thu, 19 Dec 2024 04:55:37 -0800 (PST) Received: from [192.168.10.27] ([151.81.118.45]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-38a1c829015sm1511678f8f.13.2024.12.19.04.55.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Dec 2024 04:55:36 -0800 (PST) Message-ID: <93e571e9-5539-454f-9335-6de8339ffd8b@redhat.com> Date: Thu, 19 Dec 2024 13:55:36 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 14/20] KVM: selftests: Collect *all* dirty entries in each dirty_log_test iteration To: Sean Christopherson , Maxim Levitsky Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Xu References: <20241214010721.2356923-1-seanjc@google.com> <20241214010721.2356923-15-seanjc@google.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/19/24 03:13, Sean Christopherson wrote: > On Tue, Dec 17, 2024, Maxim Levitsky wrote: >> While this patch might improve coverage for this particular case, >> I think that this patch will make the test to be much more deterministic, > > The verification will be more deterministic, but the actual testcase itself is > just as random as it was before. Based on my recollection of designing this thing with Peter, I can "confirm" that there was no particular intention of making the verification more random. >> and thus have less chance of catching various races in the kernel that can happen. >> >> In fact in my option I prefer moving this test in other direction by >> verifying dirty ring while the *vCPU runs* as well, in other words, not >> stopping the vCPU at all unless its dirty ring is full. > > But letting the vCPU-under-test keep changing the memory while it's being validated > would add significant complexity, without any benefit insofar as I can see. As > evidenced by the bug the current approach can't detect, heavily stressing the > system is meaningless if it's impossible to separate the signal from the noise. Yes, I agree. Paolo