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Protected mode assumes that at minimum vgic-v3 is present, however KVM fails to actually enforce this at the time of initialization. As such, when running protected mode in a half-baked state on GICv2 hardware we see the hyp go belly up at vcpu_load() when it tries to restore the vgic-v3 cpuif: $ ./arch_timer_edge_cases [ 130.599140] kvm [4518]: nVHE hyp panic at: [<ffff800081102b58>] __kvm_nvhe___vgic_v3_restore_vmcr_aprs+0x8/0x84! [ 130.603685] kvm [4518]: Cannot dump pKVM nVHE stacktrace: !CONFIG_PROTECTED_NVHE_STACKTRACE [ 130.611962] kvm [4518]: Hyp Offset: 0xfffeca95ed000000 [ 130.617053] Kernel panic - not syncing: HYP panic: [ 130.617053] PS:800003c9 PC:0000b56a94102b58 ESR:0000000002000000 [ 130.617053] FAR:ffff00007b98d4d0 HPFAR:00000000007b98d0 PAR:0000000000000000 [ 130.617053] VCPU:0000000000000000 [ 130.638013] CPU: 0 UID: 0 PID: 4518 Comm: arch_timer_edge Tainted: G C 6.13.0-rc3-00009-gf7d03fcbf1f4 #1 [ 130.648790] Tainted: [C]=CRAP [ 130.651721] Hardware name: Libre Computer AML-S905X-CC (DT) [ 130.657242] Call trace: [ 130.659656] show_stack+0x18/0x24 (C) [ 130.663279] dump_stack_lvl+0x38/0x90 [ 130.666900] dump_stack+0x18/0x24 [ 130.670178] panic+0x388/0x3e8 [ 130.673196] nvhe_hyp_panic_handler+0x104/0x208 [ 130.677681] kvm_arch_vcpu_load+0x290/0x548 [ 130.681821] vcpu_load+0x50/0x80 [ 130.685013] kvm_arch_vcpu_ioctl_run+0x30/0x868 [ 130.689498] kvm_vcpu_ioctl+0x2e0/0x974 [ 130.693293] __arm64_sys_ioctl+0xb4/0xec [ 130.697174] invoke_syscall+0x48/0x110 [ 130.700883] el0_svc_common.constprop.0+0x40/0xe0 [ 130.705540] do_el0_svc+0x1c/0x28 [ 130.708818] el0_svc+0x30/0xd0 [ 130.711837] el0t_64_sync_handler+0x10c/0x138 [ 130.716149] el0t_64_sync+0x198/0x19c [ 130.719774] SMP: stopping secondary CPUs [ 130.723660] Kernel Offset: disabled [ 130.727103] CPU features: 0x000,00000800,02800000,0200421b [ 130.732537] Memory Limit: none [ 130.735561] ---[ end Kernel panic - not syncing: HYP panic: [ 130.735561] PS:800003c9 PC:0000b56a94102b58 ESR:0000000002000000 [ 130.735561] FAR:ffff00007b98d4d0 HPFAR:00000000007b98d0 PAR:0000000000000000 [ 130.735561] VCPU:0000000000000000 ]--- Fix it by failing KVM initialization if the system doesn't implement vgic-v3, as protected mode will never do anything useful on such hardware. Reported-by: Mark Brown <broonie@kernel.org> Closes: https://lore.kernel.org/kvmarm/5ca7588c-7bf2-4352-8661-e4a56a9cd9aa@sirena.org.uk/ Signed-off-by: Oliver Upton <oliver.upton@linux.dev> Link: https://lore.kernel.org/r/20250203231543.233511-1-oliver.upton@linux.dev Signed-off-by: Marc Zyngier <maz@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.