From 27d2b47eef033f1fc6c0452dc1017e43dad5fe14 Mon Sep 17 00:00:00 2001 From: Yingchao Deng Date: Tue, 2 Sep 2025 11:48:25 +0800 Subject: [PATCH] KVM: arm64: Return early from trace helpers when KVM isn't available When Linux is booted at EL1, host_data_ptr() resolves to the nVHE hypervisor's copy of host data. When hyp mode isn't available for KVM the nVHE percpu bases remain uninitialized. Consequently, any usage of host_data_ptr() will result in a NULL dereference which has been observed in KVM's trace filtering helpers. Add an early return to the trace filtering helpers if KVM isn't initialized, avoiding the NULL dereference. Take this opportunity to move the TRBE-skipping checks to a common helper. Fixes: 054b88391bbe2 ("KVM: arm64: Support trace filtering for guests") Signed-off-by: Yingchao Deng Reviewed-by: James Clark [maz: repainted the helpers to be readable, and the commit message with Oliver's suggestion] Signed-off-by: Marc Zyngier --- arch/arm64/kvm/debug.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c index 381382c19fe47..1aaeb40a9a388 100644 --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c @@ -230,29 +230,29 @@ void kvm_debug_handle_oslar(struct kvm_vcpu *vcpu, u64 val) preempt_enable(); } -void kvm_enable_trbe(void) +static bool skip_trbe_access(bool skip_condition) { - if (has_vhe() || is_protected_kvm_enabled() || - WARN_ON_ONCE(preemptible())) - return; + return (WARN_ON_ONCE(preemptible()) || skip_condition || + is_protected_kvm_enabled() || !is_kvm_arm_initialised()); +} - host_data_set_flag(TRBE_ENABLED); +void kvm_enable_trbe(void) +{ + if (!skip_trbe_access(has_vhe())) + host_data_set_flag(TRBE_ENABLED); } EXPORT_SYMBOL_GPL(kvm_enable_trbe); void kvm_disable_trbe(void) { - if (has_vhe() || is_protected_kvm_enabled() || - WARN_ON_ONCE(preemptible())) - return; - - host_data_clear_flag(TRBE_ENABLED); + if (!skip_trbe_access(has_vhe())) + host_data_clear_flag(TRBE_ENABLED); } EXPORT_SYMBOL_GPL(kvm_disable_trbe); void kvm_tracing_set_el1_configuration(u64 trfcr_while_in_guest) { - if (is_protected_kvm_enabled() || WARN_ON_ONCE(preemptible())) + if (skip_trbe_access(false)) return; if (has_vhe()) { -- 2.47.3