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Fuad TabbaMarc Zyngier
Fuad Tabba
authored and
Marc Zyngier
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KVM: arm64: Initialize trap registers for protected VMs
Protected VMs have more restricted features that need to be trapped. Moreover, the host should not be trusted to set the appropriate trapping registers and their values. Initialize the trapping registers, i.e., hcr_el2, mdcr_el2, and cptr_el2 at EL2 for protected guests, based on the values of the guest's feature id registers. No functional change intended as trap handlers introduced in the previous patch are still not hooked in to the guest exit handlers. Reviewed-by: Andrew Jones <[email protected]> Signed-off-by: Fuad Tabba <[email protected]> Signed-off-by: Marc Zyngier <[email protected]> Link: https://lore.kernel.org/r/[email protected]
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‎arch/arm64/include/asm/kvm_asm.h

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@@ -64,6 +64,7 @@
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#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector 18
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#define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 19
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#define __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc 20
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#define __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_init_traps 21
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#ifndef __ASSEMBLY__
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‎arch/arm64/include/asm/kvm_host.h

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@@ -780,6 +780,8 @@ static inline bool kvm_vm_is_protected(struct kvm *kvm)
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return false;
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}
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void kvm_init_protected_traps(struct kvm_vcpu *vcpu);
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int kvm_arm_vcpu_finalize(struct kvm_vcpu *vcpu, int feature);
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bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
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‎arch/arm64/kvm/arm.c

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@@ -620,6 +620,14 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
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ret = kvm_arm_pmu_v3_enable(vcpu);
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/*
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* Initialize traps for protected VMs.
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* NOTE: Move to run in EL2 directly, rather than via a hypercall, once
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* the code is in place for first run initialization at EL2.
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*/
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if (kvm_vm_is_protected(kvm))
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kvm_call_hyp_nvhe(__pkvm_vcpu_init_traps, vcpu);
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return ret;
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}
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‎arch/arm64/kvm/hyp/include/nvhe/trap_handler.h

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@@ -15,4 +15,6 @@
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#define DECLARE_REG(type, name, ctxt, reg) \
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type name = (type)cpu_reg(ctxt, (reg))
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void __pkvm_vcpu_init_traps(struct kvm_vcpu *vcpu);
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#endif /* __ARM64_KVM_NVHE_TRAP_HANDLER_H__ */

‎arch/arm64/kvm/hyp/nvhe/Makefile

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@@ -14,7 +14,7 @@ lib-objs := $(addprefix ../../../lib/, $(lib-objs))
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obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
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hyp-main.o hyp-smp.o psci-relay.o early_alloc.o stub.o page_alloc.o \
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cache.o setup.o mm.o mem_protect.o sys_regs.o
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cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o
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obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
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../fpsimd.o ../hyp-entry.o ../exception.o ../pgtable.o
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obj-y += $(lib-objs)

‎arch/arm64/kvm/hyp/nvhe/hyp-main.c

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@@ -160,6 +160,14 @@ static void handle___pkvm_prot_finalize(struct kvm_cpu_context *host_ctxt)
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{
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cpu_reg(host_ctxt, 1) = __pkvm_prot_finalize();
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}
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static void handle___pkvm_vcpu_init_traps(struct kvm_cpu_context *host_ctxt)
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{
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DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1);
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__pkvm_vcpu_init_traps(kern_hyp_va(vcpu));
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}
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typedef void (*hcall_t)(struct kvm_cpu_context *);
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#define HANDLE_FUNC(x) [__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x
@@ -185,6 +193,7 @@ static const hcall_t host_hcall[] = {
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HANDLE_FUNC(__pkvm_host_share_hyp),
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HANDLE_FUNC(__pkvm_create_private_mapping),
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HANDLE_FUNC(__pkvm_prot_finalize),
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HANDLE_FUNC(__pkvm_vcpu_init_traps),
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};
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static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)

‎arch/arm64/kvm/hyp/nvhe/pkvm.c

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@@ -0,0 +1,186 @@
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2021 Google LLC
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* Author: Fuad Tabba <[email protected]>
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*/
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#include <linux/kvm_host.h>
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#include <linux/mm.h>
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#include <asm/kvm_fixed_config.h>
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#include <nvhe/sys_regs.h>
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#include <nvhe/trap_handler.h>
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/*
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* Set trap register values based on features in ID_AA64PFR0.
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*/
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static void pvm_init_traps_aa64pfr0(struct kvm_vcpu *vcpu)
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{
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const u64 feature_ids = get_pvm_id_aa64pfr0(vcpu);
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u64 hcr_set = HCR_RW;
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u64 hcr_clear = 0;
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u64 cptr_set = 0;
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/* Protected KVM does not support AArch32 guests. */
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BUILD_BUG_ON(FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_EL0),
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PVM_ID_AA64PFR0_RESTRICT_UNSIGNED) != ID_AA64PFR0_ELx_64BIT_ONLY);
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BUILD_BUG_ON(FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1),
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PVM_ID_AA64PFR0_RESTRICT_UNSIGNED) != ID_AA64PFR0_ELx_64BIT_ONLY);
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/*
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* Linux guests assume support for floating-point and Advanced SIMD. Do
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* not change the trapping behavior for these from the KVM default.
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*/
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BUILD_BUG_ON(!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_FP),
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PVM_ID_AA64PFR0_ALLOW));
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BUILD_BUG_ON(!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_ASIMD),
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PVM_ID_AA64PFR0_ALLOW));
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/* Trap RAS unless all current versions are supported */
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if (FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_RAS), feature_ids) <
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ID_AA64PFR0_RAS_V1P1) {
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hcr_set |= HCR_TERR | HCR_TEA;
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hcr_clear |= HCR_FIEN;
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}
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/* Trap AMU */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_AMU), feature_ids)) {
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hcr_clear |= HCR_AMVOFFEN;
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cptr_set |= CPTR_EL2_TAM;
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}
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/* Trap SVE */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_SVE), feature_ids))
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cptr_set |= CPTR_EL2_TZ;
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vcpu->arch.hcr_el2 |= hcr_set;
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vcpu->arch.hcr_el2 &= ~hcr_clear;
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vcpu->arch.cptr_el2 |= cptr_set;
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}
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/*
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* Set trap register values based on features in ID_AA64PFR1.
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*/
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static void pvm_init_traps_aa64pfr1(struct kvm_vcpu *vcpu)
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{
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const u64 feature_ids = get_pvm_id_aa64pfr1(vcpu);
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u64 hcr_set = 0;
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u64 hcr_clear = 0;
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/* Memory Tagging: Trap and Treat as Untagged if not supported. */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR1_MTE), feature_ids)) {
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hcr_set |= HCR_TID5;
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hcr_clear |= HCR_DCT | HCR_ATA;
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}
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vcpu->arch.hcr_el2 |= hcr_set;
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vcpu->arch.hcr_el2 &= ~hcr_clear;
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}
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/*
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* Set trap register values based on features in ID_AA64DFR0.
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*/
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static void pvm_init_traps_aa64dfr0(struct kvm_vcpu *vcpu)
83+
{
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const u64 feature_ids = get_pvm_id_aa64dfr0(vcpu);
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u64 mdcr_set = 0;
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u64 mdcr_clear = 0;
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u64 cptr_set = 0;
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/* Trap/constrain PMU */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_PMUVER), feature_ids)) {
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mdcr_set |= MDCR_EL2_TPM | MDCR_EL2_TPMCR;
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mdcr_clear |= MDCR_EL2_HPME | MDCR_EL2_MTPME |
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MDCR_EL2_HPMN_MASK;
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}
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/* Trap Debug */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_DEBUGVER), feature_ids))
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mdcr_set |= MDCR_EL2_TDRA | MDCR_EL2_TDA | MDCR_EL2_TDE;
99+
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/* Trap OS Double Lock */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_DOUBLELOCK), feature_ids))
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mdcr_set |= MDCR_EL2_TDOSA;
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/* Trap SPE */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_PMSVER), feature_ids)) {
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mdcr_set |= MDCR_EL2_TPMS;
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mdcr_clear |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT;
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}
109+
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/* Trap Trace Filter */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_TRACE_FILT), feature_ids))
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mdcr_set |= MDCR_EL2_TTRF;
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/* Trap Trace */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_TRACEVER), feature_ids))
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cptr_set |= CPTR_EL2_TTA;
117+
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vcpu->arch.mdcr_el2 |= mdcr_set;
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vcpu->arch.mdcr_el2 &= ~mdcr_clear;
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vcpu->arch.cptr_el2 |= cptr_set;
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}
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/*
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* Set trap register values based on features in ID_AA64MMFR0.
125+
*/
126+
static void pvm_init_traps_aa64mmfr0(struct kvm_vcpu *vcpu)
127+
{
128+
const u64 feature_ids = get_pvm_id_aa64mmfr0(vcpu);
129+
u64 mdcr_set = 0;
130+
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/* Trap Debug Communications Channel registers */
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if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64MMFR0_FGT), feature_ids))
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mdcr_set |= MDCR_EL2_TDCC;
134+
135+
vcpu->arch.mdcr_el2 |= mdcr_set;
136+
}
137+
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/*
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* Set trap register values based on features in ID_AA64MMFR1.
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*/
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static void pvm_init_traps_aa64mmfr1(struct kvm_vcpu *vcpu)
142+
{
143+
const u64 feature_ids = get_pvm_id_aa64mmfr1(vcpu);
144+
u64 hcr_set = 0;
145+
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/* Trap LOR */
147+
if (!FIELD_GET(ARM64_FEATURE_MASK(ID_AA64MMFR1_LOR), feature_ids))
148+
hcr_set |= HCR_TLOR;
149+
150+
vcpu->arch.hcr_el2 |= hcr_set;
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}
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/*
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* Set baseline trap register values.
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*/
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static void pvm_init_trap_regs(struct kvm_vcpu *vcpu)
157+
{
158+
const u64 hcr_trap_feat_regs = HCR_TID3;
159+
const u64 hcr_trap_impdef = HCR_TACR | HCR_TIDCP | HCR_TID1;
160+
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/*
162+
* Always trap:
163+
* - Feature id registers: to control features exposed to guests
164+
* - Implementation-defined features
165+
*/
166+
vcpu->arch.hcr_el2 |= hcr_trap_feat_regs | hcr_trap_impdef;
167+
168+
/* Clear res0 and set res1 bits to trap potential new features. */
169+
vcpu->arch.hcr_el2 &= ~(HCR_RES0);
170+
vcpu->arch.mdcr_el2 &= ~(MDCR_EL2_RES0);
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vcpu->arch.cptr_el2 |= CPTR_NVHE_EL2_RES1;
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vcpu->arch.cptr_el2 &= ~(CPTR_NVHE_EL2_RES0);
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}
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/*
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* Initialize trap register values for protected VMs.
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*/
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void __pkvm_vcpu_init_traps(struct kvm_vcpu *vcpu)
179+
{
180+
pvm_init_trap_regs(vcpu);
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pvm_init_traps_aa64pfr0(vcpu);
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pvm_init_traps_aa64pfr1(vcpu);
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pvm_init_traps_aa64dfr0(vcpu);
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pvm_init_traps_aa64mmfr0(vcpu);
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pvm_init_traps_aa64mmfr1(vcpu);
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}

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