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([2a01:e0a:f0e:9070:527b:9dff:feef:3874]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a5324638e9sm14406721f8f.89.2025.06.11.01.50.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Jun 2025 01:50:06 -0700 (PDT) Message-ID: <05680827-85d9-4ebd-91a7-93e262da52f5@redhat.com> Date: Wed, 11 Jun 2025 10:50:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 02/25] hw/arm/virt: Introduce machine state acpi pcihp flags and props Content-Language: en-US To: Igor Mammedov Cc: eric.auger.pro@gmail.com, qemu-devel@nongnu.org, qemu-arm@nongnu.org, peter.maydell@linaro.org, gustavo.romero@linaro.org, anisinha@redhat.com, mst@redhat.com, shannon.zhaosl@gmail.com, pbonzini@redhat.com, Jonathan.Cameron@huawei.com, philmd@linaro.org, alex.bennee@linaro.org References: <20250527074224.1197793-1-eric.auger@redhat.com> <20250527074224.1197793-3-eric.auger@redhat.com> <20250527135813.2d6cde91@imammedo.users.ipa.redhat.com> <20250528123325.750529a4@imammedo.users.ipa.redhat.com> <13792b72-d336-41b8-8ac7-8790e10f833c@redhat.com> <20250611104511.55152616@imammedo.users.ipa.redhat.com> From: Eric Auger In-Reply-To: <20250611104511.55152616@imammedo.users.ipa.redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; 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 Igor, On 6/11/25 10:45 AM, Igor Mammedov wrote: > On Wed, 11 Jun 2025 08:53:28 +0200 > Eric Auger wrote: > >> Hi Gustavo, Alex, >> >> On 5/28/25 12:33 PM, Igor Mammedov wrote: >>> On Tue, 27 May 2025 15:54:15 +0200 >>> Eric Auger wrote: >>> >>>> Hi Igor, >>>> >>>> On 5/27/25 1:58 PM, Igor Mammedov wrote: >>>>> On Tue, 27 May 2025 09:40:04 +0200 >>>>> Eric Auger wrote: >>>>> >>>>>> acpi_pcihp VirtMachineClass state flag will allow >>>>>> to opt in for acpi pci hotplug. This is guarded by a >>>>>> class no_acpi_pcihp flag to manage compats (<= 10.0 >>>>>> machine types will not support ACPI PCI hotplug). >>>>> there is no reason to put an effort in force disabling it >>>>> on old machines, as long as code works when explicitly >>>>> enabled property on CLI. >>>>> >>>>> See comment below on how to deal with it >>>>> >>>>>> Machine state acpi_pcihp flag must be set before the creation >>>>>> of the GED device which will use it. >>>>>> >>>>>> Currently the ACPI PCI HP is turned off by default. This will >>>>>> change later on for 10.1 machine type. >>>>> one thing to note, is that turning it on by default might >>>>> cause change of NIC naming in guest as this brings in >>>>> new "_Sxx" slot naming. /so configs tied to nic go down the drain/ >>>>> >>>>> Naming, we have, also happens to be broken wrt spec >>>>> (it should be unique system wide, there was a gitlab issue for that, >>>>> there is no easy fix that though) >>>>> >>>>> So I'd leave it disabled by default and let users to turn >>>>> it on explicitly when needed. >>>> what is the status on q35, isn't it enabled by default? If so why >>>> wouldn't we want the same setting on ARM? Is that because of the known >>>> issue you report above? >>> Above issue is not a blocker (for thae lack of a good way to fix it) >>> >>> on q35 we have had a few complains and fixes, after pcihp was promoted >>> to default (so hopefully that won't happen on with ARM). Also given >>> that ARM VM is less popular like hood breaking someone setup is even less. >>> >>> That said I'd be cautions keep native hotplug as default, >>> and only ones who need ACPI one, could turn it on explicitly. >>> >>> But well it's policies, so it's up to you ARM folks to decide what >>> virt board should look like. >> What is your preference? Do you prefer enabling ACPI PCI HP by default >> or the opposite. > I'd prefer native PCIe hotplug being default, > that way we have less chance of causing regressions not to mention > less complexity (as acpi pcihp adds up quite a bit of it). > > And ones who want/need acpi-pcihp/acpi-index can enable it explicitly, > to play with. OK I will follow your suggestion. You have definitively more expertise than me here ! ;-) Thanks! Eric > >> Anybody else? >> >> On my end I think I would prefer to have the same default setting than >> on x86 (ie. ACPI PCI hotplug set by default) but I have no strong >> opinion either. >> >> Thanks >> >> Eric >>> >>>> The no_foo compat stuff was especially introduced to avoid breaking the >>>> guest ABI for old machine types (like the NIC naming alternation you evoke). >>> no_foo is just another way to handle compat stuff, >>> and when it's more than one knob per feature it gets ugly really fast. >>> Hence, I'd prefer pcihp done in x86 way aka: >>> hw_compat_OLD(ged.use_acpi_hotplug_bridge, false|true) >>> to manage presence of ACPI hotplug on desired machine version. >>> Side benefit it's consistent with how pcihp works on x86 >>> >>>>> >>>>>> We also introduce properties to allow disabling it. >>>>>> >>>>>> Signed-off-by: Eric Auger >>>>>> Reviewed-by: Gustavo Romero >>>>>> --- >>>>>> include/hw/arm/virt.h | 2 ++ >>>>>> hw/arm/virt.c | 27 +++++++++++++++++++++++++++ >>>>>> 2 files changed, 29 insertions(+) >>>>>> >>>>>> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h >>>>>> index 9a1b0f53d2..10ea581f06 100644 >>>>>> --- a/include/hw/arm/virt.h >>>>>> +++ b/include/hw/arm/virt.h >>>>>> @@ -129,6 +129,7 @@ struct VirtMachineClass { >>>>>> bool no_tcg_lpa2; >>>>>> bool no_ns_el2_virt_timer_irq; >>>>>> bool no_nested_smmu; >>>>>> + bool no_acpi_pcihp; >>>>>> }; >>>>>> >>>>>> struct VirtMachineState { >>>>>> @@ -150,6 +151,7 @@ struct VirtMachineState { >>>>>> bool mte; >>>>>> bool dtb_randomness; >>>>>> bool second_ns_uart_present; >>>>>> + bool acpi_pcihp; >>>>>> OnOffAuto acpi; >>>>>> VirtGICType gic_version; >>>>>> VirtIOMMUType iommu; >>>>>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c >>>>>> index 9a6cd085a3..a0deeaf2b3 100644 >>>>>> --- a/hw/arm/virt.c >>>>>> +++ b/hw/arm/virt.c >>>>>> @@ -2397,8 +2397,10 @@ static void machvirt_init(MachineState *machine) >>>>>> create_pcie(vms); >>>>>> >>>>>> if (has_ged && aarch64 && firmware_loaded && virt_is_acpi_enabled(vms)) { >>>>>> + vms->acpi_pcihp &= !vmc->no_acpi_pcihp; >>>>> I don't particularly like no_foo naming as it makes code harder to read >>>>> and combined with 'duplicated' field in machine state it make even things worse. >>>>> (if I recall right Philippe was cleaning mess similar flags usage >>>>> have introduced with ITS) >>>>> >>>>> instead of adding machine property (both class and state), >>>>> I'd suggest adding the only property to GPE device (akin to what we have in x86 world) >>>>> And then one can meddle with defaults using hw_compat_xxx >>>> no_foo still is a largely used pattern in arm virt: no_ged, >>>> kvm_no_adjvtime, no_kvm_steal_time, no_tcg_lpa2, ../.. There are plenty >>>> of them and I am not under the impression this is going to be changed. >>>> >>>> If you refer to 8d23b1df7212 ("hw/arm/virt: Remove >>>> VirtMachineClass::no_its field") I think the no_its was removed because >>>> the machine it applied was removed. >>>> >>>> If I understand correctly you would like the prop to be attached to the >>>> GED device. However the GED device is internally created by the virt >>>> machine code and not passed through a "-device" CLI option. So how would >>>> you pass the option on the cmd line if you don't want it to be set by >>>> default per machine type? >>>> >>>> Thanks >>>> >>>> Eric >>>>> >>>>>> vms->acpi_dev = create_acpi_ged(vms); >>>>>> } else { >>>>>> + vms->acpi_pcihp = false; >>>>>> create_gpio_devices(vms, VIRT_GPIO, sysmem); >>>>>> } >>>>>> >>>>>> @@ -2593,6 +2595,20 @@ static void virt_set_its(Object *obj, bool value, Error **errp) >>>>>> vms->its = value; >>>>>> } >>>>>> >>>>>> +static bool virt_get_acpi_pcihp(Object *obj, Error **errp) >>>>>> +{ >>>>>> + VirtMachineState *vms = VIRT_MACHINE(obj); >>>>>> + >>>>>> + return vms->acpi_pcihp; >>>>>> +} >>>>>> + >>>>>> +static void virt_set_acpi_pcihp(Object *obj, bool value, Error **errp) >>>>>> +{ >>>>>> + VirtMachineState *vms = VIRT_MACHINE(obj); >>>>>> + >>>>>> + vms->acpi_pcihp = value; >>>>>> +} >>>>>> + >>>>>> static bool virt_get_dtb_randomness(Object *obj, Error **errp) >>>>>> { >>>>>> VirtMachineState *vms = VIRT_MACHINE(obj); >>>>>> @@ -3310,6 +3326,10 @@ static void virt_machine_class_init(ObjectClass *oc, const void *data) >>>>>> "in ACPI table header." >>>>>> "The string may be up to 8 bytes in size"); >>>>>> >>>>>> + object_class_property_add_bool(oc, "acpi-pcihp", >>>>>> + virt_get_acpi_pcihp, virt_set_acpi_pcihp); >>>>>> + object_class_property_set_description(oc, "acpi-pcihp", >>>>>> + "Force ACPI PCI hotplug"); >>>>>> } >>>>>> >>>>>> static void virt_instance_init(Object *obj) >>>>>> @@ -3344,6 +3364,9 @@ static void virt_instance_init(Object *obj) >>>>>> vms->tcg_its = true; >>>>>> } >>>>>> >>>>>> + /* default disallows ACPI PCI hotplug */ >>>>>> + vms->acpi_pcihp = false; >>>>>> + >>>>>> /* Default disallows iommu instantiation */ >>>>>> vms->iommu = VIRT_IOMMU_NONE; >>>>>> >>>>>> @@ -3394,8 +3417,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(10, 1) >>>>>> >>>>>> static void virt_machine_10_0_options(MachineClass *mc) >>>>>> { >>>>>> + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); >>>>>> + >>>>>> virt_machine_10_1_options(mc); >>>>>> compat_props_add(mc->compat_props, hw_compat_10_0, hw_compat_10_0_len); >>>>>> + /* 10.0 and earlier do not support ACPI PCI hotplug */ >>>>>> + vmc->no_acpi_pcihp = true; >>>>>> } >>>>>> DEFINE_VIRT_MACHINE(10, 0) >>>>>>