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-rw-r--r--arch/arm64/kvm/debug.c344
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diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
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+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Debug and Guest Debug support
+ *
+ * Copyright (C) 2015 - Linaro Ltd
+ * Author: Alex Bennée <alex.bennee@linaro.org>
+ */
+
+#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(u64, 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.
+ *
+ * When single-step is enabled by userspace, we tweak PSTATE.SS on every
+ * guest entry. Preserve PSTATE.SS so we can restore the original value
+ * for the vcpu after the single-step is disabled.
+ */
+static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
+{
+ u64 val = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
+
+ vcpu->arch.guest_debug_preserved.mdscr_el1 = val;
+
+ trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
+ vcpu->arch.guest_debug_preserved.mdscr_el1);
+
+ vcpu->arch.guest_debug_preserved.pstate_ss =
+ (*vcpu_cpsr(vcpu) & DBG_SPSR_SS);
+}
+
+static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
+{
+ u64 val = vcpu->arch.guest_debug_preserved.mdscr_el1;
+
+ vcpu_write_sys_reg(vcpu, val, MDSCR_EL1);
+
+ trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
+ vcpu_read_sys_reg(vcpu, MDSCR_EL1));
+
+ if (vcpu->arch.guest_debug_preserved.pstate_ss)
+ *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+ else
+ *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
+}
+
+/**
+ * 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_ret(__kvm_get_mdcr_el2));
+}
+
+/**
+ * kvm_arm_setup_mdcr_el2 - configure vcpu mdcr_el2 value
+ *
+ * @vcpu: the vcpu pointer
+ *
+ * This 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)
+ * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
+ * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF)
+ * - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB)
+ */
+static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
+{
+ /*
+ * This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK
+ * to disable guest access to the profiling and trace buffers
+ */
+ vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
+ vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
+ MDCR_EL2_TPMS |
+ MDCR_EL2_TTRF |
+ MDCR_EL2_TPMCR |
+ MDCR_EL2_TDRA |
+ MDCR_EL2_TDOSA);
+
+ /* Is the VM being debugged by userspace? */
+ if (vcpu->guest_debug)
+ /* Route all software debug exceptions to EL2 */
+ vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
+
+ /*
+ * Trap debug register access when one of the following is true:
+ * - Userspace is using the hardware to debug the guest
+ * (KVM_GUESTDBG_USE_HW is set).
+ * - The guest is not using debug (DEBUG_DIRTY clear).
+ * - The guest has enabled the OS Lock (debug exceptions are blocked).
+ */
+ if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) ||
+ !vcpu_get_flag(vcpu, DEBUG_DIRTY) ||
+ kvm_vcpu_os_lock_enabled(vcpu))
+ vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
+
+ trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
+}
+
+/**
+ * kvm_arm_vcpu_init_debug - setup vcpu debug traps
+ *
+ * @vcpu: the vcpu pointer
+ *
+ * Set vcpu initial mdcr_el2 value.
+ */
+void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu)
+{
+ preempt_disable();
+ kvm_arm_setup_mdcr_el2(vcpu);
+ preempt_enable();
+}
+
+/**
+ * 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.
+ *
+ * Additionally, KVM only traps guest accesses to the debug registers if
+ * the guest is not actively using them (see the DEBUG_DIRTY
+ * flag on vcpu->arch.iflags). 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)
+{
+ unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2;
+
+ trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
+
+ kvm_arm_setup_mdcr_el2(vcpu);
+
+ /* Check if we need to use the debug registers. */
+ if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
+ /* 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) {
+ /*
+ * If the software step state at the last guest exit
+ * was Active-pending, we don't set DBG_SPSR_SS so
+ * that the state is maintained (to not run another
+ * single-step until the pending Software Step
+ * exception is taken).
+ */
+ if (!vcpu_get_flag(vcpu, DBG_SS_ACTIVE_PENDING))
+ *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+ else
+ *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
+
+ mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
+ mdscr |= DBG_MDSCR_SS;
+ vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
+ } else {
+ mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
+ mdscr &= ~DBG_MDSCR_SS;
+ vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
+ }
+
+ 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 DEBUG_DIRTY mechanism ensures
+ * the registers are updated on the world switch.
+ */
+ if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
+ /* Enable breakpoints/watchpoints */
+ mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
+ mdscr |= DBG_MDSCR_MDE;
+ vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
+
+ vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
+ vcpu_set_flag(vcpu, DEBUG_DIRTY);
+
+ 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]);
+
+ /*
+ * The OS Lock blocks debug exceptions in all ELs when it is
+ * enabled. If the guest has enabled the OS Lock, constrain its
+ * effects to the guest. Emulate the behavior by clearing
+ * MDSCR_EL1.MDE. In so doing, we ensure that host debug
+ * exceptions are unaffected by guest configuration of the OS
+ * Lock.
+ */
+ } else if (kvm_vcpu_os_lock_enabled(vcpu)) {
+ mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
+ mdscr &= ~DBG_MDSCR_MDE;
+ vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
+ }
+ }
+
+ BUG_ON(!vcpu->guest_debug &&
+ vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
+
+ /* If KDE or MDE are set, perform a full save/restore cycle. */
+ if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE))
+ vcpu_set_flag(vcpu, 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("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
+}
+
+void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
+{
+ trace_kvm_arm_clear_debug(vcpu->guest_debug);
+
+ /*
+ * Restore the guest's debug registers if we were using them.
+ */
+ if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
+ if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+ if (!(*vcpu_cpsr(vcpu) & DBG_SPSR_SS))
+ /*
+ * Mark the vcpu as ACTIVE_PENDING
+ * until Software Step exception is taken.
+ */
+ vcpu_set_flag(vcpu, DBG_SS_ACTIVE_PENDING);
+ }
+
+ 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]);
+ }
+ }
+}
+
+void kvm_arch_vcpu_load_debug_state_flags(struct kvm_vcpu *vcpu)
+{
+ u64 dfr0;
+
+ /* For VHE, there is nothing to do */
+ if (has_vhe())
+ return;
+
+ dfr0 = read_sysreg(id_aa64dfr0_el1);
+ /*
+ * If SPE is present on this CPU and is available at current EL,
+ * we may need to check if the host state needs to be saved.
+ */
+ if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMSVer_SHIFT) &&
+ !(read_sysreg_s(SYS_PMBIDR_EL1) & BIT(SYS_PMBIDR_EL1_P_SHIFT)))
+ vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_SPE);
+
+ /* Check if we have TRBE implemented and available at the host */
+ if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceBuffer_SHIFT) &&
+ !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_PROG))
+ vcpu_set_flag(vcpu, DEBUG_STATE_SAVE_TRBE);
+}
+
+void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu)
+{
+ vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_SPE);
+ vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRBE);
+}