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From: | Suthikulpanit, Suravee |
Subject: | Re: [PATCH v2] pc: q35: Bump max_cpus to 1024 |
Date: | Thu, 1 Jun 2023 14:54:54 -0700 |
User-agent: | Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 |
On 6/1/2023 6:09 PM, Michael S. Tsirkin wrote:
On Thu, Jun 01, 2023 at 11:17:30AM +0100, Daniel P. Berrangé wrote:On Thu, Jun 01, 2023 at 11:09:45AM +0100, Joao Martins wrote:>> The need for the 64-bit entry point depends on a combination of RAMOn 31/05/2023 23:51, Suravee Suthikulpanit wrote:Since KVM_MAX_VCPUS is currently defined to 1024 for x86 as shown in arch/x86/include/asm/kvm_host.h, update QEMU limits to the same number. In case KVM could not support the specified number of vcpus, QEMU would return the following error message: qemu-system-x86_64: kvm_init_vcpu: kvm_get_vcpu failed (xxx): Invalid argument Signed-off-by: Suravee Suthikulpanit<suravee.suthikulpanit@amd.com> --- Changes from V1: (https://lore.kernel.org/all/YnkDGsIi1vFvXmiP@redhat.com/T/) * Bump from 512 to KVM_MAX_VCPUS (per Igor's suggestion) Note: From the last discussion, Daniel mentioned that SMBIO 2.1 tables might cause overflow at approx 720 CPUs, and it might require using the SMBIO 3.0 entry point. Also, we might need to change the default for the x86 machine type to SMBIO 3.0. However, I do not know the status of this.I suspect smbios 3.0 (64-bit entry point) is already supported. With current qemu and all the smbios fixes in the last cycle, perhaps this is mainly just setting smbios_entry_point_type to SMBIOS_ENTRY_POINT_TYPE_64 if MachineState::smp::max_cpus is bigger than 720 (e.g. in pc_q35_init()?)
config
and CPU count. IMHO we need to unconditionally switch the latest machine types to use the 64-bit entry point by default, rather than trying to infer some special condition to dynamically change on the fly.Yes, makes sense.
Thanks all for the feedback. So, IIUC, here is how the SMBIOS entry point types would be affected by the QEMU options:
- pc-q35-8.1 and later, default to SMBIOS EP type 64. - pc-q35-8.0 and older, default to SMBIOS EP type 32.- User can override the type w/ QEMU option "-M .., smbios-entry-point-type=[32|64]"
Please let me know if I am missing anything. If this is accurate, I'll send out v3 with this change.
Thanks, Suravee
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