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87727ba2bb
Although pKVM supports CPU PMU emulation for non-protected guests since722625c6f4("KVM: arm64: Reenable pmu in Protected Mode"), this relies on the PMU driver probing before the host has de-privileged so that the 'kvm_arm_pmu_available' static key can still be enabled by patching the hypervisor text. As it happens, both of these events hang off device_initcall() but the PMU consistently won the race until7755cec63a("arm64: perf: Move PMUv3 driver to drivers/perf"). Since then, the host will fail to boot when pKVM is enabled: | hw perfevents: enabled with armv8_pmuv3_0 PMU driver, 7 counters available | kvm [1]: nVHE hyp BUG at: [<ffff8000090366e0>] __kvm_nvhe_handle_host_mem_abort+0x270/0x284! | kvm [1]: Cannot dump pKVM nVHE stacktrace: !CONFIG_PROTECTED_NVHE_STACKTRACE | kvm [1]: Hyp Offset: 0xfffea41fbdf70000 | Kernel panic - not syncing: HYP panic: | PS:a00003c9 PC:0000dbe04b0c66e0 ESR:00000000f2000800 | FAR:fffffbfffddfcf00 HPFAR:00000000010b0bf0 PAR:0000000000000000 | VCPU:0000000000000000 | CPU: 2 PID: 1 Comm: swapper/0 Not tainted 6.3.0-rc7-00083-g0bce6746d154 #1 | Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 | Call trace: | dump_backtrace+0xec/0x108 | show_stack+0x18/0x2c | dump_stack_lvl+0x50/0x68 | dump_stack+0x18/0x24 | panic+0x13c/0x33c | nvhe_hyp_panic_handler+0x10c/0x190 | aarch64_insn_patch_text_nosync+0x64/0xc8 | arch_jump_label_transform+0x4c/0x5c | __jump_label_update+0x84/0xfc | jump_label_update+0x100/0x134 | static_key_enable_cpuslocked+0x68/0xac | static_key_enable+0x20/0x34 | kvm_host_pmu_init+0x88/0xa4 | armpmu_register+0xf0/0xf4 | arm_pmu_acpi_probe+0x2ec/0x368 | armv8_pmu_driver_init+0x38/0x44 | do_one_initcall+0xcc/0x240 Fix the race properly by deferring the de-privilege step to device_initcall_sync(). This will also be needed in future when probing IOMMU devices and allows us to separate the pKVM de-privilege logic from the core hypervisor initialisation path. Cc: Oliver Upton <oliver.upton@linux.dev> Cc: Fuad Tabba <tabba@google.com> Cc: Marc Zyngier <maz@kernel.org> Fixes:7755cec63a("arm64: perf: Move PMUv3 driver to drivers/perf") Tested-by: Fuad Tabba <tabba@google.com> Acked-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20230420123356.2708-1-will@kernel.org Signed-off-by: Will Deacon <will@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 Restructured Text 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.