[Qemu-devel] [RFC v3 0/3] KVM/ARM: Fix >256 vcpus

[Eric Auger <eric.auger@redhat.com>]

Since 4.18, KVM/ARM exposes a KVM_MAX_VCPUS equal to 512. However it was
reported [1] that a VM with more than 256 vcpus cannot be launched. 5.4
is about to fix the situation with 2 patches:
- one upgrade of the KVM_IRQ_LINE API [2] supporting a vcpu id encoded
  on 12 bits,
- the reduction of KVM IO devices consumed by each GICv3 redistributor [3]

This series uses the new KVM_IRQ_LINE API and also checks the associated
capability (KVM_CAP_ARM_IRQ_LINE_LAYOUT_2) in machvirt.

Without the series, as soon as the -smp arguments exceeds 256, QEMU exits
with "kvm_set_irq: Invalid argument".

Best Regards

Eric

References:
[1] Can we boot a 512U kvm guest?
    https://patchwork.kernel.org/patch/11091501/
[2] [PATCH] KVM: arm/arm64: vgic: Allow more than 256 vcpus for KVM_IRQ_LINE
    https://patchwork.kernel.org/patch/11099609/
[3] [PATCH] KVM: arm/arm64: vgic: Use a single IO device per redistributor
    https://patchwork.kernel.org/patch/11112141/

This series can be found at:
https://github.com/eauger/qemu/tree/v4.1.0-256fix-rfc-v3

History:
v2 -> v3:
- simplifications in kvm_arm_gic_set_irq
- Implement KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 check in kvm_arch_init

v1 -> v2:
- New layout set for kvm_arm_gic_set_irq and
  arm_cpu_kvm_set_irq through kvm_arm_set_irq
- Introduced kvm_arm_irq_line_layout_mismatch()

Eric Auger (3):
  linux headers: update for KVM_CAP_ARM_IRQ_LINE_LAYOUT_2
  intc/arm_gic: Support IRQ injection for more than 256 vpus
  ARM: KVM: Check KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 for smp_cpus > 256

 hw/intc/arm_gic_kvm.c                        |  7 ++---
 include/standard-headers/asm-x86/bootparam.h |  2 ++
 include/standard-headers/asm-x86/kvm_para.h  |  1 +
 include/standard-headers/linux/ethtool.h     |  2 ++
 include/standard-headers/linux/pci_regs.h    |  4 +++
 include/standard-headers/linux/virtio_ids.h  |  1 +
 include/standard-headers/linux/virtio_pmem.h |  6 ++---
 linux-headers/asm-arm/kvm.h                  | 16 ++++++++++-
 linux-headers/asm-arm/unistd-common.h        |  2 ++
 linux-headers/asm-arm64/kvm.h                | 21 ++++++++++++++-
 linux-headers/asm-generic/mman-common.h      | 15 ++++++-----
 linux-headers/asm-generic/mman.h             | 10 +++----
 linux-headers/asm-generic/unistd.h           |  8 +++++-
 linux-headers/asm-mips/unistd_n32.h          |  1 +
 linux-headers/asm-mips/unistd_n64.h          |  1 +
 linux-headers/asm-mips/unistd_o32.h          |  1 +
 linux-headers/asm-powerpc/mman.h             |  6 +----
 linux-headers/asm-powerpc/unistd_32.h        |  2 ++
 linux-headers/asm-powerpc/unistd_64.h        |  2 ++
 linux-headers/asm-s390/unistd_32.h           |  2 ++
 linux-headers/asm-s390/unistd_64.h           |  2 ++
 linux-headers/asm-x86/kvm.h                  | 28 +++++++++++++++-----
 linux-headers/asm-x86/unistd_32.h            |  2 ++
 linux-headers/asm-x86/unistd_64.h            |  2 ++
 linux-headers/asm-x86/unistd_x32.h           |  2 ++
 linux-headers/linux/kvm.h                    | 12 ++++++---
 linux-headers/linux/psp-sev.h                |  5 +---
 target/arm/cpu.c                             | 10 +++----
 target/arm/kvm.c                             | 22 ++++++++++++++-
 target/arm/kvm_arm.h                         |  1 +
 30 files changed, 147 insertions(+), 49 deletions(-)

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2.20.1