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Thu, 19 Dec 2024 07:01:34 -0800 (PST) X-Google-Smtp-Source: AGHT+IH2N9TF1k63Od4kikgXEkYiTMrQAPSa5Hk4ZXuksk3JLSjxWMWr1eWQIHuzkEKx2sEfTJNzWg== X-Received: by 2002:a05:6e02:1c81:b0:3a7:c3aa:a82b with SMTP id e9e14a558f8ab-3bdc003e775mr61833965ab.1.1734620494562; Thu, 19 Dec 2024 07:01:34 -0800 (PST) Received: from starship ([2607:fea8:fc01:8d8d:6adb:55ff:feaa:b156]) by smtp.gmail.com with ESMTPSA id e9e14a558f8ab-3c0deccf373sm3542685ab.28.2024.12.19.07.01.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Dec 2024 07:01:33 -0800 (PST) Message-ID: <680a0b7b95b9300d2972246fbfd93f000ce0c0be.camel@redhat.com> Subject: Re: [PATCH 14/20] KVM: selftests: Collect *all* dirty entries in each dirty_log_test iteration From: Maxim Levitsky To: Paolo Bonzini , Sean Christopherson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Xu Date: Thu, 19 Dec 2024 10:01:32 -0500 In-Reply-To: <93e571e9-5539-454f-9335-6de8339ffd8b@redhat.com> References: <20241214010721.2356923-1-seanjc@google.com> <20241214010721.2356923-15-seanjc@google.com> <93e571e9-5539-454f-9335-6de8339ffd8b@redhat.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit On Thu, 2024-12-19 at 13:55 +0100, Paolo Bonzini wrote: > 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 > In this case I don't have any objections. Best regards, Maxim Levitsky