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* [PATCH 0/5] KVM: arm64: GICv5 legacy (GCIE_LEGACY) NV enablement and cleanup
@ 2025-08-28 10:59 Sascha Bischoff
  2025-08-28 10:59 ` [PATCH 3/5] arm64: cpucaps: Add GICv5 Legacy vCPU interface (GCIE_LEGACY) capability Sascha Bischoff
                   ` (5 more replies)
  0 siblings, 6 replies; 10+ messages in thread
From: Sascha Bischoff @ 2025-08-28 10:59 UTC (permalink / raw)
  To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org
  Cc: nd, maz@kernel.org, oliver.upton@linux.dev, Joey Gouly,
	Suzuki Poulose, yuzenghui@huawei.com, will@kernel.org,
	tglx@linutronix.de, lpieralisi@kernel.org, Timothy Hayes

Hi all,

This series enables nested virtualization for GICv3-based VMs on GICv5
hosts (w/ FEAT_GCIE_LEGACY) in KVM/arm64. In addition, it adds a CPU
capability to track support for FEAT_GCIE_LEGACY across all CPUs.

The series fixes ICC_SRE_EL2 access handling for GICv5 hosts (to match
the updated bet1+ specification [1]), and extends nested
virtualization support to vGICv3 guests running on compatible GICv5
systems. With these changes, it becomes possible to run with
kvm-arm.mode=nested, and these changes have been tested with three
levels of nesting on simulated hardware (Arm FVP).

Previously, the presence of FEAT_GCIE_LEGACY was tracked in the GICv5
driver via gic_kvm_info, and the probing logic could incorrectly
enable legacy support if the boot CPU exposed the feature while others
did not. This created the risk of mismatched configurations,
particularly when late-onlining CPUs without FEAT_GCIE_LEGACY.

To address this, the series introduces a proper ARM64_HAS_GICV5_LEGACY
CPU capability, and moves KVM to use cpus_have_final_cap() to ensure
consistent system-wide enablement. With this, late-onlined but
mismatched CPUs are cleanly rejected at bring-up.

Patch summary

KVM: arm64: allow ICC_SRE_EL2 accesses on a GICv5 host
    Update handling to reflect the corrected GICv5 specification.

KVM: arm64: Enable nested for GICv5 host with FEAT_GCIE_LEGACY
    Allow nested virtualization for vGICv3 guests on GICv5 hosts with
    legacy support.

arm64: cpucaps: Add GICv5 Legacy vCPU interface (GCIE_LEGACY) capability
    Introduce a new CPU capability that prevents mismatched
    configurations.

KVM: arm64: Use ARM64_HAS_GICV5_LEGACY for GICv5 probing
    Ensure probing is consistent across all CPUs by using cpucaps.

irqchip/gic-v5: Drop has_gcie_v3_compat from gic_kvm_info
    Remove obsolete compatibility flag, as FEAT_GCIE_LEGACY is now a
    CPU feature.

Comments and reviews are very welcome.

Thanks,
Sascha

[1] https://developer.arm.com/documentation/aes0070/latest/

Sascha Bischoff (5):
  KVM: arm64: Allow ICC_SRE_EL2 accesses on a GICv5 host
  KVM: arm64: Enable nested for GICv5 host with FEAT_GCIE_LEGACY
  arm64: cpucaps: Add GICv5 Legacy vCPU interface (GCIE_LEGACY)
    capability
  KVM: arm64: Use ARM64_HAS_GICV5_LEGACY for GICv5 probing
  irqchip/gic-v5: Drop has_gcie_v3_compat from gic_kvm_info

 arch/arm64/kernel/cpufeature.c        | 15 +++++++++++++++
 arch/arm64/kvm/arm.c                  |  5 +++--
 arch/arm64/kvm/hyp/vgic-v3-sr.c       | 27 +++++++--------------------
 arch/arm64/kvm/vgic/vgic-v5.c         |  2 +-
 arch/arm64/tools/cpucaps              |  1 +
 drivers/irqchip/irq-gic-v5.c          |  7 -------
 include/linux/irqchip/arm-vgic-info.h |  2 --
 7 files changed, 27 insertions(+), 32 deletions(-)

-- 
2.34.1

^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2025-09-04  9:34 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-08-28 10:59 [PATCH 0/5] KVM: arm64: GICv5 legacy (GCIE_LEGACY) NV enablement and cleanup Sascha Bischoff
2025-08-28 10:59 ` [PATCH 3/5] arm64: cpucaps: Add GICv5 Legacy vCPU interface (GCIE_LEGACY) capability Sascha Bischoff
2025-09-02  8:23   ` Suzuki K Poulose
2025-08-28 10:59 ` [PATCH 2/5] KVM: arm64: Enable nested for GICv5 host with FEAT_GCIE_LEGACY Sascha Bischoff
2025-08-28 10:59 ` [PATCH 4/5] KVM: arm64: Use ARM64_HAS_GICV5_LEGACY for GICv5 probing Sascha Bischoff
2025-08-28 10:59 ` [PATCH 1/5] KVM: arm64: Allow ICC_SRE_EL2 accesses on a GICv5 host Sascha Bischoff
2025-08-28 14:05   ` Marc Zyngier
2025-08-28 10:59 ` [PATCH 5/5] irqchip/gic-v5: Drop has_gcie_v3_compat from gic_kvm_info Sascha Bischoff
2025-09-03 12:07   ` Thomas Gleixner
2025-09-04  7:57 ` [PATCH 0/5] KVM: arm64: GICv5 legacy (GCIE_LEGACY) NV enablement and cleanup Oliver Upton

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