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([2a01:e0a:59e:9d80:527b:9dff:feef:3874]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43cfad9b823sm27522235e9.5.2025.03.10.07.53.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Mar 2025 07:53:16 -0700 (PDT) Message-ID: Date: Mon, 10 Mar 2025 15:53:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 09/21] hw/vfio/pci: Convert CONFIG_KVM check to runtime one Content-Language: en-US To: BALATON Zoltan Cc: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org, Yi Liu , Pierrick Bouvier , Alex Williamson , Christian Borntraeger , =?UTF-8?Q?Alex_Benn=C3=A9e?= , Tony Krowiak , Nicholas Piggin , Halil Pasic , Thomas Huth , David Hildenbrand , Igor Mammedov , Matthew Rosato , Tomita Moeko , qemu-ppc@nongnu.org, Daniel Henrique Barboza , Eric Farman , Eduardo Habkost , Peter Xu , kvm@vger.kernel.org, Zhenzhong Duan , qemu-s390x@nongnu.org, Paolo Bonzini , Harsh Prateek Bora , =?UTF-8?Q?C=C3=A9dric_Le_Goater?= , Ilya Leoshkevich , Jason Herne , =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= , Richard Henderson References: <20250308230917.18907-1-philmd@linaro.org> <20250308230917.18907-10-philmd@linaro.org> <28c102c1-d157-4d22-a351-9fcc8f4260fd@redhat.com> <2d44848e-01c1-25c5-dfcb-99f5112fcbd7@eik.bme.hu> From: Eric Auger In-Reply-To: <2d44848e-01c1-25c5-dfcb-99f5112fcbd7@eik.bme.hu> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=eric.auger@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: eric.auger@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi, On 3/10/25 1:54 PM, BALATON Zoltan wrote: > On Mon, 10 Mar 2025, Eric Auger wrote: >> Hi Philippe, >> >> On 3/9/25 12:09 AM, Philippe Mathieu-Daudé wrote: >>> Use the runtime kvm_enabled() helper to check whether >>> KVM is available or not. >> >> Miss the "why" of this patch. >> >> By the way I fail to remember/see where kvm_allowed is set. > > It's in include/system/kvm.h There you can only find the kvm_enabled() macro definition. I was eventually able to locate it: accel/accel-system.c:    *(acc->allowed) = true; in accel_init_machine() > >> I am also confused because we still have some code, like in >> vfio/common.c which does both checks: >> #ifdef CONFIG_KVM >>         if (kvm_enabled()) { >>             max_memslots = kvm_get_max_memslots(); >>         } >> #endif > > I think this is because if KVM is not available the if cannot be true > so it can be left out altogether. This may make sense on platforms > like Windows and macOS where QEMU is compiled without KVM so basically > everywhere except Linux. But in practice we have a stub for kvm_get_max_memslots in accel/stubs/kvm-stub.c. Eric > > Regards, > BALATON Zoltan