--- /dev/null
+/*
+ * Debug and Guest Debug support
+ *
+ * Copyright (C) 2015 - Linaro Ltd
+ * Author: Alex Bennée <alex.bennee@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/hw_breakpoint.h>
+
+#include <asm/debug-monitors.h>
+#include <asm/kvm_asm.h>
+#include <asm/kvm_arm.h>
+#include <asm/kvm_emulate.h>
+
+#include "trace.h"
+
+/* These are the bits of MDSCR_EL1 we may manipulate */
+#define MDSCR_EL1_DEBUG_MASK (DBG_MDSCR_SS | \
+ DBG_MDSCR_KDE | \
+ DBG_MDSCR_MDE)
+
+static DEFINE_PER_CPU(u32, mdcr_el2);
+
+/**
+ * save/restore_guest_debug_regs
+ *
+ * For some debug operations we need to tweak some guest registers. As
+ * a result we need to save the state of those registers before we
+ * make those modifications.
+ *
+ * Guest access to MDSCR_EL1 is trapped by the hypervisor and handled
+ * after we have restored the preserved value to the main context.
+ */
+static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
+{
+ vcpu->arch.guest_debug_preserved.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1);
+
+ trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
+ vcpu->arch.guest_debug_preserved.mdscr_el1);
+}
+
+static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
+{
+ vcpu_sys_reg(vcpu, MDSCR_EL1) = vcpu->arch.guest_debug_preserved.mdscr_el1;
+
+ trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
+ vcpu_sys_reg(vcpu, MDSCR_EL1));
+}
+
+/**
+ * kvm_arm_init_debug - grab what we need for debug
+ *
+ * Currently the sole task of this function is to retrieve the initial
+ * value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has
+ * presumably been set-up by some knowledgeable bootcode.
+ *
+ * It is called once per-cpu during CPU hyp initialisation.
+ */
+
+void kvm_arm_init_debug(void)
+{
+ __this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
+}
+
+/**
+ * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state
+ */
+
+void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
+{
+ vcpu->arch.debug_ptr = &vcpu->arch.vcpu_debug_state;
+}
+
+/**
+ * kvm_arm_setup_debug - set up debug related stuff
+ *
+ * @vcpu: the vcpu pointer
+ *
+ * This is called before each entry into the hypervisor to setup any
+ * debug related registers. Currently this just ensures we will trap
+ * access to:
+ * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
+ * - Debug ROM Address (MDCR_EL2_TDRA)
+ * - OS related registers (MDCR_EL2_TDOSA)
+ *
+ * Additionally, KVM only traps guest accesses to the debug registers if
+ * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
+ * flag on vcpu->arch.debug_flags). Since the guest must not interfere
+ * with the hardware state when debugging the guest, we must ensure that
+ * trapping is enabled whenever we are debugging the guest using the
+ * debug registers.
+ */
+
+void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
+{
+ bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);
+
+ trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
+
+ vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
+ vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
+ MDCR_EL2_TPMCR |
+ MDCR_EL2_TDRA |
+ MDCR_EL2_TDOSA);
+
+ /* Is Guest debugging in effect? */
+ if (vcpu->guest_debug) {
+ /* Route all software debug exceptions to EL2 */
+ vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
+
+ /* Save guest debug state */
+ save_guest_debug_regs(vcpu);
+
+ /*
+ * Single Step (ARM ARM D2.12.3 The software step state
+ * machine)
+ *
+ * If we are doing Single Step we need to manipulate
+ * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the
+ * step has occurred the hypervisor will trap the
+ * debug exception and we return to userspace.
+ *
+ * If the guest attempts to single step its userspace
+ * we would have to deal with a trapped exception
+ * while in the guest kernel. Because this would be
+ * hard to unwind we suppress the guest's ability to
+ * do so by masking MDSCR_EL.SS.
+ *
+ * This confuses guest debuggers which use
+ * single-step behind the scenes but everything
+ * returns to normal once the host is no longer
+ * debugging the system.
+ */
+ if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+ *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+ vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS;
+ } else {
+ vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS;
+ }
+
+ trace_kvm_arm_set_dreg32("SPSR_EL2", *vcpu_cpsr(vcpu));
+
+ /*
+ * HW Breakpoints and watchpoints
+ *
+ * We simply switch the debug_ptr to point to our new
+ * external_debug_state which has been populated by the
+ * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
+ * mechanism ensures the registers are updated on the
+ * world switch.
+ */
+ if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
+ /* Enable breakpoints/watchpoints */
+ vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_MDE;
+
+ vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
+ vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
+ trap_debug = true;
+
+ trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
+ &vcpu->arch.debug_ptr->dbg_bcr[0],
+ &vcpu->arch.debug_ptr->dbg_bvr[0]);
+
+ trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
+ &vcpu->arch.debug_ptr->dbg_wcr[0],
+ &vcpu->arch.debug_ptr->dbg_wvr[0]);
+ }
+ }
+
+ BUG_ON(!vcpu->guest_debug &&
+ vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
+
+ /* Trap debug register access */
+ if (trap_debug)
+ vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
+
+ trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
+ trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_sys_reg(vcpu, MDSCR_EL1));
+}
+
+void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
+{
+ trace_kvm_arm_clear_debug(vcpu->guest_debug);
+
+ if (vcpu->guest_debug) {
+ restore_guest_debug_regs(vcpu);
+
+ /*
+ * If we were using HW debug we need to restore the
+ * debug_ptr to the guest debug state.
+ */
+ if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
+ kvm_arm_reset_debug_ptr(vcpu);
+
+ trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
+ &vcpu->arch.debug_ptr->dbg_bcr[0],
+ &vcpu->arch.debug_ptr->dbg_bvr[0]);
+
+ trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
+ &vcpu->arch.debug_ptr->dbg_wcr[0],
+ &vcpu->arch.debug_ptr->dbg_wvr[0]);
+ }
+ }
+}
Code Review / kvmfornfv.git / blobdiff