From 87727ba2bb05cc3cb4233231faa7ab4c7eeb6c73 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 20 Apr 2023 13:33:56 +0100 Subject: KVM: arm64: Ensure CPU PMU probes before pKVM host de-privilege Although pKVM supports CPU PMU emulation for non-protected guests since 722625c6f4c5 ("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 until 7755cec63ade ("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: [] __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 Cc: Fuad Tabba Cc: Marc Zyngier Fixes: 7755cec63ade ("arm64: perf: Move PMUv3 driver to drivers/perf") Tested-by: Fuad Tabba Acked-by: Marc Zyngier Link: https://lore.kernel.org/r/20230420123356.2708-1-will@kernel.org Signed-off-by: Will Deacon --- arch/arm64/kvm/pkvm.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) (limited to 'arch/arm64/kvm/pkvm.c') diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c index cf56958b1492..6e9ece1ebbe7 100644 --- a/arch/arm64/kvm/pkvm.c +++ b/arch/arm64/kvm/pkvm.c @@ -4,6 +4,8 @@ * Author: Quentin Perret */ +#include +#include #include #include #include @@ -13,6 +15,8 @@ #include "hyp_constants.h" +DEFINE_STATIC_KEY_FALSE(kvm_protected_mode_initialized); + static struct memblock_region *hyp_memory = kvm_nvhe_sym(hyp_memory); static unsigned int *hyp_memblock_nr_ptr = &kvm_nvhe_sym(hyp_memblock_nr); @@ -213,3 +217,46 @@ int pkvm_init_host_vm(struct kvm *host_kvm) mutex_init(&host_kvm->lock); return 0; } + +static void __init _kvm_host_prot_finalize(void *arg) +{ + int *err = arg; + + if (WARN_ON(kvm_call_hyp_nvhe(__pkvm_prot_finalize))) + WRITE_ONCE(*err, -EINVAL); +} + +static int __init pkvm_drop_host_privileges(void) +{ + int ret = 0; + + /* + * Flip the static key upfront as that may no longer be possible + * once the host stage 2 is installed. + */ + static_branch_enable(&kvm_protected_mode_initialized); + on_each_cpu(_kvm_host_prot_finalize, &ret, 1); + return ret; +} + +static int __init finalize_pkvm(void) +{ + int ret; + + if (!is_protected_kvm_enabled()) + return 0; + + /* + * Exclude HYP sections from kmemleak so that they don't get peeked + * at, which would end badly once inaccessible. + */ + kmemleak_free_part(__hyp_bss_start, __hyp_bss_end - __hyp_bss_start); + kmemleak_free_part_phys(hyp_mem_base, hyp_mem_size); + + ret = pkvm_drop_host_privileges(); + if (ret) + pr_err("Failed to finalize Hyp protection: %d\n", ret); + + return ret; +} +device_initcall_sync(finalize_pkvm); -- cgit v1.2.3