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Thu, 19 Dec 2024 10:02:09 -0800 (PST) X-Google-Smtp-Source: AGHT+IHUU1KHjceG82PmHIi7w1ZKI46aTucVDJ9DAkST3r+nn79jP/qXPNTfiY2pNtpDN8zX3weYAA== X-Received: by 2002:a5d:6d0e:0:b0:385:ec6e:e872 with SMTP id ffacd0b85a97d-38a223f714cmr11451f8f.38.1734631329354; Thu, 19 Dec 2024 10:02:09 -0800 (PST) Received: from [192.168.1.84] ([93.56.163.127]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-38a1c8a6cb1sm2124424f8f.89.2024.12.19.10.02.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Dec 2024 10:02:08 -0800 (PST) Message-ID: Date: Thu, 19 Dec 2024 19:02:05 +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 v5 3/3] KVM: x86: add new nested vmexit tracepoints To: Maxim Levitsky , kvm@vger.kernel.org Cc: x86@kernel.org, Dave Hansen , Thomas Gleixner , Borislav Petkov , Ingo Molnar , Sean Christopherson , "H. Peter Anvin" , linux-kernel@vger.kernel.org References: <20240910200350.264245-1-mlevitsk@redhat.com> <20240910200350.264245-4-mlevitsk@redhat.com> <9ff2be87-117a-4f96-af3b-dacb55467449@redhat.com> <4c1c999c29809c683cc79bc8c77cbe5d7eca37b7.camel@redhat.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: <4c1c999c29809c683cc79bc8c77cbe5d7eca37b7.camel@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/19/24 18:49, Maxim Levitsky wrote: >> Here I probably would have preferred an unconditional tracepoint giving >> RAX/RBX/RCX/RDX after a nested vmexit. This is not exactly what Sean >> wanted but perhaps it strikes a middle ground? I know you wrote this >> for a debugging tool, do you really need to have everything in a single >> tracepoint, or can you correlate the existing exit tracepoint with this >> hypothetical trace_kvm_nested_exit_regs, to pick RDMSR vs. WRMSR? > > Hi! > > If the new trace_kvm_nested_exit_regs tracepoint has a VM exit number argument, then > I can enable this new tracepoint twice with a different filter (vm_exit_num number == msr and vm_exit_num == vmcall), > and each instance will count the events that I need. > > So this can work. Ok, thanks. On one hand it may make sense to have trace_kvm_exit_regs and trace_kvm_nested_exit_regs (you can even extend the TRACE_EVENT_KVM_EXIT macro to generate both the exit and the exit_regs tracepoint). On the other hand it seems to me that this new tracepoint is kinda reinventing the wheel; your patch adding nested equivalents of trace_kvm_hypercall and trace_kvm_msr seems more obvious to me. I see Sean's point in not wanting one-off tracepoints, on the other hand there is value in having similar tracepoints for the L1->L0 and L2->L0 cases. I'll let him choose between the two possibilities (a new *_exit_regs pair, or just apply this patch) but I think there should be one of these two. Paolo