1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Debug and Guest Debug support 4 * 5 * Copyright (C) 2015 - Linaro Ltd 6 * Authors: Alex Bennée <alex.bennee@linaro.org> 7 * Oliver Upton <oliver.upton@linux.dev> 8 */ 9 10 #include <linux/kvm_host.h> 11 #include <linux/hw_breakpoint.h> 12 13 #include <asm/debug-monitors.h> 14 #include <asm/kvm_asm.h> 15 #include <asm/kvm_arm.h> 16 #include <asm/kvm_emulate.h> 17 18 /** 19 * kvm_arm_setup_mdcr_el2 - configure vcpu mdcr_el2 value 20 * 21 * @vcpu: the vcpu pointer 22 * 23 * This ensures we will trap access to: 24 * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR) 25 * - Debug ROM Address (MDCR_EL2_TDRA) 26 * - OS related registers (MDCR_EL2_TDOSA) 27 * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB) 28 * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF) 29 * - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB) 30 */ 31 static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu) 32 { 33 preempt_disable(); 34 35 /* 36 * This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK 37 * to disable guest access to the profiling and trace buffers 38 */ 39 vcpu->arch.mdcr_el2 = FIELD_PREP(MDCR_EL2_HPMN, 40 *host_data_ptr(nr_event_counters)); 41 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM | 42 MDCR_EL2_TPMS | 43 MDCR_EL2_TTRF | 44 MDCR_EL2_TPMCR | 45 MDCR_EL2_TDRA | 46 MDCR_EL2_TDOSA); 47 48 /* Is the VM being debugged by userspace? */ 49 if (vcpu->guest_debug) 50 /* Route all software debug exceptions to EL2 */ 51 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; 52 53 /* 54 * Trap debug registers if the guest doesn't have ownership of them. 55 */ 56 if (!kvm_guest_owns_debug_regs(vcpu)) 57 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; 58 59 /* Write MDCR_EL2 directly if we're already at EL2 */ 60 if (has_vhe()) 61 write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2); 62 63 preempt_enable(); 64 } 65 66 void kvm_init_host_debug_data(void) 67 { 68 u64 dfr0 = read_sysreg(id_aa64dfr0_el1); 69 70 if (cpuid_feature_extract_signed_field(dfr0, ID_AA64DFR0_EL1_PMUVer_SHIFT) > 0) 71 *host_data_ptr(nr_event_counters) = FIELD_GET(ARMV8_PMU_PMCR_N, 72 read_sysreg(pmcr_el0)); 73 74 *host_data_ptr(debug_brps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, dfr0); 75 *host_data_ptr(debug_wrps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr0); 76 77 if (has_vhe()) 78 return; 79 80 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMSVer_SHIFT) && 81 !(read_sysreg_s(SYS_PMBIDR_EL1) & PMBIDR_EL1_P)) 82 host_data_set_flag(HAS_SPE); 83 84 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceBuffer_SHIFT) && 85 !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_EL1_P)) 86 host_data_set_flag(HAS_TRBE); 87 } 88 89 /* 90 * Configures the 'external' MDSCR_EL1 value for the guest, i.e. when the host 91 * has taken over MDSCR_EL1. 92 * 93 * - Userspace is single-stepping the guest, and MDSCR_EL1.SS is forced to 1. 94 * 95 * - Userspace is using the breakpoint/watchpoint registers to debug the 96 * guest, and MDSCR_EL1.MDE is forced to 1. 97 * 98 * - The guest has enabled the OS Lock, and KVM is forcing MDSCR_EL1.MDE to 0, 99 * masking all debug exceptions affected by the OS Lock. 100 */ 101 static void setup_external_mdscr(struct kvm_vcpu *vcpu) 102 { 103 /* 104 * Use the guest's MDSCR_EL1 as a starting point, since there are 105 * several other features controlled by MDSCR_EL1 that are not relevant 106 * to the host. 107 * 108 * Clear the bits that KVM may use which also satisfies emulation of 109 * the OS Lock as MDSCR_EL1.MDE is cleared. 110 */ 111 u64 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1) & ~(MDSCR_EL1_SS | 112 MDSCR_EL1_MDE | 113 MDSCR_EL1_KDE); 114 115 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) 116 mdscr |= MDSCR_EL1_SS; 117 118 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) 119 mdscr |= MDSCR_EL1_MDE | MDSCR_EL1_KDE; 120 121 vcpu->arch.external_mdscr_el1 = mdscr; 122 } 123 124 void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu) 125 { 126 u64 mdscr; 127 128 /* Must be called before kvm_vcpu_load_vhe() */ 129 KVM_BUG_ON(vcpu_get_flag(vcpu, SYSREGS_ON_CPU), vcpu->kvm); 130 131 /* 132 * Determine which of the possible debug states we're in: 133 * 134 * - VCPU_DEBUG_HOST_OWNED: KVM has taken ownership of the guest's 135 * breakpoint/watchpoint registers, or needs to use MDSCR_EL1 to do 136 * software step or emulate the effects of the OS Lock being enabled. 137 * 138 * - VCPU_DEBUG_GUEST_OWNED: The guest has debug exceptions enabled, and 139 * the breakpoint/watchpoint registers need to be loaded eagerly. 140 * 141 * - VCPU_DEBUG_FREE: Neither of the above apply, no breakpoint/watchpoint 142 * context needs to be loaded on the CPU. 143 */ 144 if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) { 145 vcpu->arch.debug_owner = VCPU_DEBUG_HOST_OWNED; 146 setup_external_mdscr(vcpu); 147 148 /* 149 * Steal the guest's single-step state machine if userspace wants 150 * single-step the guest. 151 */ 152 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { 153 if (*vcpu_cpsr(vcpu) & DBG_SPSR_SS) 154 vcpu_clear_flag(vcpu, GUEST_SS_ACTIVE_PENDING); 155 else 156 vcpu_set_flag(vcpu, GUEST_SS_ACTIVE_PENDING); 157 158 if (!vcpu_get_flag(vcpu, HOST_SS_ACTIVE_PENDING)) 159 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; 160 else 161 *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS; 162 } 163 } else { 164 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1); 165 166 if (mdscr & (MDSCR_EL1_KDE | MDSCR_EL1_MDE)) 167 vcpu->arch.debug_owner = VCPU_DEBUG_GUEST_OWNED; 168 else 169 vcpu->arch.debug_owner = VCPU_DEBUG_FREE; 170 } 171 172 kvm_arm_setup_mdcr_el2(vcpu); 173 } 174 175 void kvm_vcpu_put_debug(struct kvm_vcpu *vcpu) 176 { 177 if (likely(!(vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP))) 178 return; 179 180 /* 181 * Save the host's software step state and restore the guest's before 182 * potentially returning to userspace. 183 */ 184 if (!(*vcpu_cpsr(vcpu) & DBG_SPSR_SS)) 185 vcpu_set_flag(vcpu, HOST_SS_ACTIVE_PENDING); 186 else 187 vcpu_clear_flag(vcpu, HOST_SS_ACTIVE_PENDING); 188 189 if (vcpu_get_flag(vcpu, GUEST_SS_ACTIVE_PENDING)) 190 *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS; 191 else 192 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; 193 } 194 195 /* 196 * Updates ownership of the debug registers after a trapped guest access to a 197 * breakpoint/watchpoint register. Host ownership of the debug registers is of 198 * strictly higher priority, and it is the responsibility of the VMM to emulate 199 * guest debug exceptions in this configuration. 200 */ 201 void kvm_debug_set_guest_ownership(struct kvm_vcpu *vcpu) 202 { 203 if (kvm_host_owns_debug_regs(vcpu)) 204 return; 205 206 vcpu->arch.debug_owner = VCPU_DEBUG_GUEST_OWNED; 207 kvm_arm_setup_mdcr_el2(vcpu); 208 } 209 210 void kvm_debug_handle_oslar(struct kvm_vcpu *vcpu, u64 val) 211 { 212 if (val & OSLAR_EL1_OSLK) 213 __vcpu_sys_reg(vcpu, OSLSR_EL1) |= OSLSR_EL1_OSLK; 214 else 215 __vcpu_sys_reg(vcpu, OSLSR_EL1) &= ~OSLSR_EL1_OSLK; 216 217 preempt_disable(); 218 kvm_arch_vcpu_put(vcpu); 219 kvm_arch_vcpu_load(vcpu, smp_processor_id()); 220 preempt_enable(); 221 } 222