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
18static int cpu_has_spe(u64 dfr0)
19{
20 return cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMSVer_SHIFT) &&
21 !(read_sysreg_s(SYS_PMBIDR_EL1) & PMBIDR_EL1_P);
22}
23
24/**
25 * kvm_arm_setup_mdcr_el2 - configure vcpu mdcr_el2 value
26 *
27 * @vcpu: the vcpu pointer
28 *
29 * This ensures we will trap access to:
30 * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR)
31 * - Debug ROM Address (MDCR_EL2_TDRA)
32 * - OS related registers (MDCR_EL2_TDOSA)
33 * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
34 * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF)
35 * - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB)
36 */
37static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
38{
39 preempt_disable();
40
41 /*
42 * This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK
43 * to disable guest access to the profiling and trace buffers
44 */
45 vcpu->arch.mdcr_el2 = FIELD_PREP(MDCR_EL2_HPMN,
46 *host_data_ptr(nr_event_counters));
47 vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
48 MDCR_EL2_TPMS |
49 MDCR_EL2_TTRF |
50 MDCR_EL2_TPMCR |
51 MDCR_EL2_TDRA |
52 MDCR_EL2_TDOSA);
53
54 /* Is the VM being debugged by userspace? */
55 if (vcpu->guest_debug)
56 /* Route all software debug exceptions to EL2 */
57 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
58
59 /*
60 * Trap debug registers if the guest doesn't have ownership of them.
61 */
62 if (!kvm_guest_owns_debug_regs(vcpu))
63 vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
64
65 if (vcpu_has_nv(vcpu))
66 kvm_nested_setup_mdcr_el2(vcpu);
67
68 /* Write MDCR_EL2 directly if we're already at EL2 */
69 if (has_vhe())
70 write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
71
72 preempt_enable();
73}
74
75void kvm_init_host_debug_data(void)
76{
77 u64 dfr0 = read_sysreg(id_aa64dfr0_el1);
78
79 if (cpuid_feature_extract_signed_field(dfr0, ID_AA64DFR0_EL1_PMUVer_SHIFT) > 0)
80 *host_data_ptr(nr_event_counters) = FIELD_GET(ARMV8_PMU_PMCR_N,
81 read_sysreg(pmcr_el0));
82
83 *host_data_ptr(debug_brps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, dfr0);
84 *host_data_ptr(debug_wrps) = SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr0);
85
86 if (cpu_has_spe(dfr0))
87 host_data_set_flag(HAS_SPE);
88
89 if (has_vhe())
90 return;
91
92 /* Check if we have BRBE implemented and available at the host */
93 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_BRBE_SHIFT))
94 host_data_set_flag(HAS_BRBE);
95
96 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceFilt_SHIFT)) {
97 /* Force disable trace in protected mode in case of no TRBE */
98 if (is_protected_kvm_enabled())
99 host_data_set_flag(EL1_TRACING_CONFIGURED);
100
101 if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceBuffer_SHIFT) &&
102 !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_EL1_P))
103 host_data_set_flag(HAS_TRBE);
104 }
105}
106
107void kvm_debug_init_vhe(void)
108{
109 /* Clear PMSCR_EL1.E{0,1}SPE which reset to UNKNOWN values. */
110 if (host_data_test_flag(HAS_SPE))
111 write_sysreg_el1(0, SYS_PMSCR);
112}
113
114/*
115 * Configures the 'external' MDSCR_EL1 value for the guest, i.e. when the host
116 * has taken over MDSCR_EL1.
117 *
118 * - Userspace is single-stepping the guest, and MDSCR_EL1.SS is forced to 1.
119 *
120 * - Userspace is using the breakpoint/watchpoint registers to debug the
121 * guest, and MDSCR_EL1.MDE is forced to 1.
122 *
123 * - The guest has enabled the OS Lock, and KVM is forcing MDSCR_EL1.MDE to 0,
124 * masking all debug exceptions affected by the OS Lock.
125 */
126static void setup_external_mdscr(struct kvm_vcpu *vcpu)
127{
128 /*
129 * Use the guest's MDSCR_EL1 as a starting point, since there are
130 * several other features controlled by MDSCR_EL1 that are not relevant
131 * to the host.
132 *
133 * Clear the bits that KVM may use which also satisfies emulation of
134 * the OS Lock as MDSCR_EL1.MDE is cleared.
135 */
136 u64 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1) & ~(MDSCR_EL1_SS |
137 MDSCR_EL1_MDE |
138 MDSCR_EL1_KDE);
139
140 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
141 mdscr |= MDSCR_EL1_SS;
142
143 if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW)
144 mdscr |= MDSCR_EL1_MDE | MDSCR_EL1_KDE;
145
146 vcpu->arch.external_mdscr_el1 = mdscr;
147}
148
149void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu)
150{
151 u64 mdscr;
152
153 /* Must be called before kvm_vcpu_load_vhe() */
154 KVM_BUG_ON(vcpu_get_flag(vcpu, SYSREGS_ON_CPU), vcpu->kvm);
155
156 if (has_vhe())
157 *host_data_ptr(host_debug_state.mdcr_el2) = read_sysreg(mdcr_el2);
158
159 /*
160 * Determine which of the possible debug states we're in:
161 *
162 * - VCPU_DEBUG_HOST_OWNED: KVM has taken ownership of the guest's
163 * breakpoint/watchpoint registers, or needs to use MDSCR_EL1 to do
164 * software step or emulate the effects of the OS Lock being enabled.
165 *
166 * - VCPU_DEBUG_GUEST_OWNED: The guest has debug exceptions enabled, and
167 * the breakpoint/watchpoint registers need to be loaded eagerly.
168 *
169 * - VCPU_DEBUG_FREE: Neither of the above apply, no breakpoint/watchpoint
170 * context needs to be loaded on the CPU.
171 */
172 if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
173 vcpu->arch.debug_owner = VCPU_DEBUG_HOST_OWNED;
174 setup_external_mdscr(vcpu);
175
176 /*
177 * Steal the guest's single-step state machine if userspace wants
178 * single-step the guest.
179 */
180 if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
181 if (*vcpu_cpsr(vcpu) & DBG_SPSR_SS)
182 vcpu_clear_flag(vcpu, GUEST_SS_ACTIVE_PENDING);
183 else
184 vcpu_set_flag(vcpu, GUEST_SS_ACTIVE_PENDING);
185
186 if (!vcpu_get_flag(vcpu, HOST_SS_ACTIVE_PENDING))
187 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
188 else
189 *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
190 }
191 } else {
192 mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
193
194 if (mdscr & (MDSCR_EL1_KDE | MDSCR_EL1_MDE))
195 vcpu->arch.debug_owner = VCPU_DEBUG_GUEST_OWNED;
196 else
197 vcpu->arch.debug_owner = VCPU_DEBUG_FREE;
198 }
199
200 kvm_arm_setup_mdcr_el2(vcpu);
201}
202
203void kvm_vcpu_put_debug(struct kvm_vcpu *vcpu)
204{
205 if (has_vhe())
206 write_sysreg(*host_data_ptr(host_debug_state.mdcr_el2), mdcr_el2);
207
208 if (likely(!(vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)))
209 return;
210
211 /*
212 * Save the host's software step state and restore the guest's before
213 * potentially returning to userspace.
214 */
215 if (!(*vcpu_cpsr(vcpu) & DBG_SPSR_SS))
216 vcpu_set_flag(vcpu, HOST_SS_ACTIVE_PENDING);
217 else
218 vcpu_clear_flag(vcpu, HOST_SS_ACTIVE_PENDING);
219
220 if (vcpu_get_flag(vcpu, GUEST_SS_ACTIVE_PENDING))
221 *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
222 else
223 *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
224}
225
226/*
227 * Updates ownership of the debug registers after a trapped guest access to a
228 * breakpoint/watchpoint register. Host ownership of the debug registers is of
229 * strictly higher priority, and it is the responsibility of the VMM to emulate
230 * guest debug exceptions in this configuration.
231 */
232void kvm_debug_set_guest_ownership(struct kvm_vcpu *vcpu)
233{
234 if (kvm_host_owns_debug_regs(vcpu))
235 return;
236
237 vcpu->arch.debug_owner = VCPU_DEBUG_GUEST_OWNED;
238 kvm_arm_setup_mdcr_el2(vcpu);
239}
240
241void kvm_debug_handle_oslar(struct kvm_vcpu *vcpu, u64 val)
242{
243 if (val & OSLAR_EL1_OSLK)
244 __vcpu_rmw_sys_reg(vcpu, OSLSR_EL1, |=, OSLSR_EL1_OSLK);
245 else
246 __vcpu_rmw_sys_reg(vcpu, OSLSR_EL1, &=, ~OSLSR_EL1_OSLK);
247
248 preempt_disable();
249 kvm_arch_vcpu_put(vcpu);
250 kvm_arch_vcpu_load(vcpu, smp_processor_id());
251 preempt_enable();
252}
253
254static bool skip_trbe_access(bool skip_condition)
255{
256 return (WARN_ON_ONCE(preemptible()) || skip_condition ||
257 is_protected_kvm_enabled() || !is_kvm_arm_initialised());
258}
259
260void kvm_enable_trbe(void)
261{
262 if (!skip_trbe_access(has_vhe()))
263 host_data_set_flag(TRBE_ENABLED);
264}
265EXPORT_SYMBOL_GPL(kvm_enable_trbe);
266
267void kvm_disable_trbe(void)
268{
269 if (!skip_trbe_access(has_vhe()))
270 host_data_clear_flag(TRBE_ENABLED);
271}
272EXPORT_SYMBOL_GPL(kvm_disable_trbe);
273
274void kvm_tracing_set_el1_configuration(u64 trfcr_while_in_guest)
275{
276 if (skip_trbe_access(skip_condition: false))
277 return;
278
279 if (has_vhe()) {
280 write_sysreg_s(trfcr_while_in_guest, SYS_TRFCR_EL12);
281 return;
282 }
283
284 *host_data_ptr(trfcr_while_in_guest) = trfcr_while_in_guest;
285 if (read_sysreg_s(SYS_TRFCR_EL1) != trfcr_while_in_guest)
286 host_data_set_flag(EL1_TRACING_CONFIGURED);
287 else
288 host_data_clear_flag(EL1_TRACING_CONFIGURED);
289}
290EXPORT_SYMBOL_GPL(kvm_tracing_set_el1_configuration);
291

source code of linux/arch/arm64/kvm/debug.c