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KVM: arm64: Don't write to Rt unless sys_reg emulation succeeds

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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
This commit is contained in:
Oliver Upton 2022-05-03 06:02:00 +00:00 committed by Marc Zyngier
parent 001bb81999
commit 28eda7b5e8
1 changed files with 16 additions and 6 deletions
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22
arch/arm64/kvm/sys_regs.c
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@ -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;
}
/******************************************************************************