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KVM: arm64: Only reset vCPU-scoped feature ID regs once
The general expecation with feature ID registers is that they're 'reset' exactly once by KVM for the lifetime of a vCPU/VM, such that any userspace changes to the CPU features / identity are honored after a vCPU gets reset (e.g. PSCI_ON). KVM handles what it calls VM-scoped feature ID registers correctly, but feature ID registers local to a vCPU (CLIDR_EL1, MPIDR_EL1) get wiped after every reset. What's especially concerning is that a potentially-changing MPIDR_EL1 breaks MPIDR compression for indexing mpidr_data, as the mask of useful bits to build the index could change. This is absolutely no good. Avoid resetting vCPU feature ID registers more than once. Signed-off-by: Oliver Upton <oliver.upton@linux.dev> Link: https://lore.kernel.org/r/20240502233529.1958459-4-oliver.upton@linux.dev Signed-off-by: Marc Zyngier <maz@kernel.org>
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@ -1275,6 +1275,8 @@ static inline bool __vcpu_has_feature(const struct kvm_arch *ka, int feature)
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#define vcpu_has_feature(v, f) __vcpu_has_feature(&(v)->kvm->arch, (f))
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#define kvm_vcpu_initialized(v) vcpu_get_flag(vcpu, VCPU_INITIALIZED)
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int kvm_trng_call(struct kvm_vcpu *vcpu);
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#ifdef CONFIG_KVM
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extern phys_addr_t hyp_mem_base;
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@ -580,11 +580,6 @@ unsigned long kvm_arch_vcpu_get_ip(struct kvm_vcpu *vcpu)
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}
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#endif
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static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
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{
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return vcpu_get_flag(vcpu, VCPU_INITIALIZED);
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}
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static void kvm_init_mpidr_data(struct kvm *kvm)
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{
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struct kvm_mpidr_data *data = NULL;
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@ -1568,6 +1568,14 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, const struct sys_reg_desc *r
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return IDREG(vcpu->kvm, reg_to_encoding(r));
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}
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static bool is_feature_id_reg(u32 encoding)
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{
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return (sys_reg_Op0(encoding) == 3 &&
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(sys_reg_Op1(encoding) < 2 || sys_reg_Op1(encoding) == 3) &&
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sys_reg_CRn(encoding) == 0 &&
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sys_reg_CRm(encoding) <= 7);
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}
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/*
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* Return true if the register's (Op0, Op1, CRn, CRm, Op2) is
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* (3, 0, 0, crm, op2), where 1<=crm<8, 0<=op2<8, which is the range of ID
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@ -1580,6 +1588,11 @@ static inline bool is_vm_ftr_id_reg(u32 id)
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sys_reg_CRm(id) < 8);
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}
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static inline bool is_vcpu_ftr_id_reg(u32 id)
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{
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return is_feature_id_reg(id) && !is_vm_ftr_id_reg(id);
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}
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static inline bool is_aa32_id_reg(u32 id)
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{
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return (sys_reg_Op0(id) == 3 && sys_reg_Op1(id) == 0 &&
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@ -3522,6 +3535,15 @@ static void reset_vm_ftr_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc
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IDREG(kvm, id) = reg->reset(vcpu, reg);
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}
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static void reset_vcpu_ftr_id_reg(struct kvm_vcpu *vcpu,
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const struct sys_reg_desc *reg)
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{
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if (kvm_vcpu_initialized(vcpu))
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return;
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reg->reset(vcpu, reg);
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}
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/**
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* kvm_reset_sys_regs - sets system registers to reset value
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* @vcpu: The VCPU pointer
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@ -3542,6 +3564,8 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
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if (is_vm_ftr_id_reg(reg_to_encoding(r)))
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reset_vm_ftr_id_reg(vcpu, r);
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else if (is_vcpu_ftr_id_reg(reg_to_encoding(r)))
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reset_vcpu_ftr_id_reg(vcpu, r);
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else
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r->reset(vcpu, r);
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}
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@ -3972,14 +3996,6 @@ int kvm_arm_copy_sys_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
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sys_reg_CRm(r), \
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sys_reg_Op2(r))
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static bool is_feature_id_reg(u32 encoding)
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{
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return (sys_reg_Op0(encoding) == 3 &&
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(sys_reg_Op1(encoding) < 2 || sys_reg_Op1(encoding) == 3) &&
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sys_reg_CRn(encoding) == 0 &&
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sys_reg_CRm(encoding) <= 7);
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}
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int kvm_vm_ioctl_get_reg_writable_masks(struct kvm *kvm, struct reg_mask_range *range)
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{
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const void *zero_page = page_to_virt(ZERO_PAGE(0));
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