73 lines
2.9 KiB
Diff
73 lines
2.9 KiB
Diff
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From b270420c34cd990b1bcbe506c3fb0ef6f76d21a8 Mon Sep 17 00:00:00 2001
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From: Ani Sinha <anisinha@redhat.com>
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Date: Wed, 8 Jan 2025 15:10:22 +0530
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Subject: [PATCH 5/7] pc: q35: Bump max_cpus to 4096 vcpus
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RH-Author: Ani Sinha <anisinha@redhat.com>
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RH-MergeRequest: 317: pc: q35: Bump max_cpus to 4096 vcpus
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RH-Jira: RHEL-57668
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [1/1] 35242a1fa8fc21f7d73422d23074cd8da5f74781 (anisinha/centos-qemu-kvm)
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This is the downstream change equivalent of the upstream QEMU commit
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e4e98c7e ("pc: q35: Bump max_cpus to 4096 vcpus")
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Since upstream Linux kernel commit
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f10a570b093e6 ("KVM: x86: Add CONFIG_KVM_MAX_NR_VCPUS to allow up to 4096 vCPUs")
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Linux kernel can support upto a maximum number of 4096 vcpus when MAXSMP is
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enabled in the kernel. This upstream change has been backported to c9s kernel
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already. Please see JIRA https://issues.redhat.com/browse/RHEL-11579 and the
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following commit authored by Vitaly Kuznetsov:
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a85f846be686b0a ("KVM: x86: Add CONFIG_KVM_MAX_NR_VCPUS to allow up to 4096 vCPUs")
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At present, QEMU has been tested to correctly boot a linux guest with 4096
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vcpus using edk2 that has the fixes corresponding to the following two upstream
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edk2 PRs:
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https://github.com/tianocore/edk2/pull/5410
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https://github.com/tianocore/edk2/pull/5418
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The changes corresponding to the above two upstream edk2 PRs has been included
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in the downstream c9s edk2 with the following MR:
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https://gitlab.com/redhat/centos-stream/src/edk2/-/merge_requests/59
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So bump up the value max_cpus to 4096 for RHEL q35 machines versions 9.6 and
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newer. Q35 RHEL machines versions 9.4 and older continue to support 710 maximum
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vcpus as before for compatibility reasons.
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See also
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https://gitlab.com/redhat/centos-stream/src/qemu-kvm/-/merge_requests/236
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https://gitlab.com/redhat/centos-stream/src/qemu-kvm/-/merge_requests/273
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Signed-off-by: Ani Sinha <anisinha@redhat.com>
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---
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hw/i386/pc_q35.c | 5 ++++-
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1 file changed, 4 insertions(+), 1 deletion(-)
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diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
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index 37f54062c8..506f9dc0c0 100644
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--- a/hw/i386/pc_q35.c
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+++ b/hw/i386/pc_q35.c
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@@ -344,7 +344,7 @@ static void pc_q35_machine_options(MachineClass *m)
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m->default_display = "std";
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m->default_nic = "e1000e";
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m->no_floppy = 1;
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- m->max_cpus = 710;
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+ m->max_cpus = 4096;
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m->no_parallel = 1;
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machine_class_allow_dynamic_sysbus_dev(m, TYPE_AMD_IOMMU_DEVICE);
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machine_class_allow_dynamic_sysbus_dev(m, TYPE_INTEL_IOMMU_DEVICE);
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@@ -698,6 +698,9 @@ static void pc_q35_rhel_machine_9_4_0_options(MachineClass *m)
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{
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PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
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pc_q35_rhel_machine_9_6_0_options(m);
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+
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+ /* older RHEL machines continue to support 710 vcpus */
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+ m->max_cpus = 710;
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m->desc = "RHEL-9.4.0 PC (Q35 + ICH9, 2009)";
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pcmc->smbios_stream_product = "RHEL";
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pcmc->smbios_stream_version = "9.4.0";
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--
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2.39.3
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