From: Andrew Murray <andrew.murray@xxxxxxx> commit 4942dc6638b07b5326b6d2faa142635c559e7cd5 upstream. On VHE systems arch.mdcr_el2 is written to mdcr_el2 at vcpu_load time to set options for self-hosted debug and the performance monitors extension. Unfortunately the value of arch.mdcr_el2 is not calculated until kvm_arm_setup_debug() in the run loop after the vcpu has been loaded. This means that the initial brief iterations of the run loop use a zero value of mdcr_el2 - until the vcpu is preempted. This also results in a delay between changes to vcpu->guest_debug taking effect. Fix this by writing to mdcr_el2 in kvm_arm_setup_debug() on VHE systems when a change to arch.mdcr_el2 has been detected. Fixes: d5a21bcc2995 ("KVM: arm64: Move common VHE/non-VHE trap config in separate functions") Cc: <stable@xxxxxxxxxxxxxxx> # 4.17.x- Suggested-by: James Morse <james.morse@xxxxxxx> Acked-by: Will Deacon <will@xxxxxxxxxx> Reviewed-by: Marc Zyngier <maz@xxxxxxxxxx> Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/kvm/debug.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c @@ -101,7 +101,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) { bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY); - unsigned long mdscr; + unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2; trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug); @@ -197,6 +197,10 @@ void kvm_arm_setup_debug(struct kvm_vcpu if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE)) vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY; + /* Write mdcr_el2 changes since vcpu_load on VHE systems */ + if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2) + write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2); + trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2); trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1)); }