Commit 28eda7b5 authored by Oliver Upton's avatar Oliver Upton Committed by Marc Zyngier
Browse files

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: default avatarOliver Upton <oupton@google.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220503060205.2823727-3-oupton@google.com
parent 001bb819

arch/arm64/kvm/sys_regs.c

+16 −6
Original line number Diff line number Diff line
@@ -2401,7 +2401,14 @@ static bool is_imp_def_sys_reg(struct sys_reg_params *params) 
	return params->Op0 == 3 && (params->CRn & 0b1011) == 0b1011;

}



static int emulate_sys_reg(struct kvm_vcpu *vcpu,

/**

 * emulate_sys_reg - Emulate a guest access to an AArch64 system register

 * @vcpu: The VCPU pointer

 * @params: Decoded system register parameters

 *

 * Return: true if the system register access was successful, false otherwise.

 */

static bool emulate_sys_reg(struct kvm_vcpu *vcpu,

			   struct sys_reg_params *params)

{

	const struct sys_reg_desc *r;
@@ -2410,7 +2417,10 @@ static int emulate_sys_reg(struct kvm_vcpu *vcpu, 


	if (likely(r)) {

		perform_access(vcpu, params, r);

	} else if (is_imp_def_sys_reg(params)) {

		return true;

	}



	if (is_imp_def_sys_reg(params)) {

		kvm_inject_undefined(vcpu);

	} else {

		print_sys_reg_msg(params,
@@ -2418,7 +2428,7 @@ static int emulate_sys_reg(struct kvm_vcpu *vcpu, 
				  *vcpu_pc(vcpu), *vcpu_cpsr(vcpu));

		kvm_inject_undefined(vcpu);

	}

	return 1;

	return false;

}



/**
@@ -2446,18 +2456,18 @@ int kvm_handle_sys_reg(struct kvm_vcpu *vcpu) 
	struct sys_reg_params params;

	unsigned long esr = kvm_vcpu_get_esr(vcpu);

	int Rt = kvm_vcpu_sys_get_rt(vcpu);

	int ret;



	trace_kvm_handle_sys_reg(esr);



	params = esr_sys64_to_params(esr);

	params.regval = vcpu_get_reg(vcpu, Rt);



	ret = emulate_sys_reg(vcpu, &params);

	if (!emulate_sys_reg(vcpu, &params))

		return 1;



	if (!params.is_write)

		vcpu_set_reg(vcpu, Rt, params.regval);

	return ret;

	return 1;

}



/******************************************************************************