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KVM: arm64: Don't write to Rt unless sys_reg emulation succeeds
emulate_sys_reg() returns 1 unconditionally, even though a a system register access can fail. Furthermore, kvm_handle_sys_reg() writes to Rt for every register read, regardless of if it actually succeeded. Though this pattern is safe (as params.regval is initialized with the current value of Rt) it is a bit ugly. Indicate failure if the register access could not be emulated and only write to Rt on success. Signed-off-by: Oliver Upton <oupton@google.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220503060205.2823727-3-oupton@google.com
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@ -2401,7 +2401,14 @@ static bool is_imp_def_sys_reg(struct sys_reg_params *params)
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return params->Op0 == 3 && (params->CRn & 0b1011) == 0b1011;
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}
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static int emulate_sys_reg(struct kvm_vcpu *vcpu,
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/**
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* emulate_sys_reg - Emulate a guest access to an AArch64 system register
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* @vcpu: The VCPU pointer
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* @params: Decoded system register parameters
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*
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* Return: true if the system register access was successful, false otherwise.
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*/
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static bool emulate_sys_reg(struct kvm_vcpu *vcpu,
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struct sys_reg_params *params)
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{
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const struct sys_reg_desc *r;
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@ -2410,7 +2417,10 @@ static int emulate_sys_reg(struct kvm_vcpu *vcpu,
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if (likely(r)) {
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perform_access(vcpu, params, r);
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} else if (is_imp_def_sys_reg(params)) {
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return true;
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}
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if (is_imp_def_sys_reg(params)) {
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kvm_inject_undefined(vcpu);
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} else {
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print_sys_reg_msg(params,
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@ -2418,7 +2428,7 @@ static int emulate_sys_reg(struct kvm_vcpu *vcpu,
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*vcpu_pc(vcpu), *vcpu_cpsr(vcpu));
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kvm_inject_undefined(vcpu);
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}
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return 1;
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return false;
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}
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/**
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@ -2446,18 +2456,18 @@ int kvm_handle_sys_reg(struct kvm_vcpu *vcpu)
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struct sys_reg_params params;
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unsigned long esr = kvm_vcpu_get_esr(vcpu);
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int Rt = kvm_vcpu_sys_get_rt(vcpu);
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int ret;
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trace_kvm_handle_sys_reg(esr);
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params = esr_sys64_to_params(esr);
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params.regval = vcpu_get_reg(vcpu, Rt);
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ret = emulate_sys_reg(vcpu, ¶ms);
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if (!emulate_sys_reg(vcpu, ¶ms))
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return 1;
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if (!params.is_write)
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vcpu_set_reg(vcpu, Rt, params.regval);
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return ret;
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return 1;
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}
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/******************************************************************************
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