[PATCH v2] KVM: arm64: Fully zero the vcpu state on reset

[Marc Zyngier <maz@kernel.org>]

On vcpu reset, we expect all the registers to be brought back
to their initial state, which happens to be a bunch of zeroes.

However, some recent commit broke this, and is now leaving a bunch
of registers (such as the FP state) with whatever was left by the
guest. My bad.

Zero the reset of the state (32bit SPSRs and FPSIMD state).

Cc: stable@vger.kernel.org
Fixes: e47c2055c68e ("KVM: arm64: Make struct kvm_regs userspace-only")
Signed-off-by: Marc Zyngier <maz@kernel.org>
---

Notes:
    v2: Only reset the FPSIMD state and the AArch32 SPSRs to avoid
    corrupting CNTVOFF in creative ways.

 arch/arm64/kvm/reset.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index bd354cd45d28..4b5acd84b8c8 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -242,6 +242,11 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 
 	/* Reset core registers */
 	memset(vcpu_gp_regs(vcpu), 0, sizeof(*vcpu_gp_regs(vcpu)));
+	memset(&vcpu->arch.ctxt.fp_regs, 0, sizeof(vcpu->arch.ctxt.fp_regs));
+	vcpu->arch.ctxt.spsr_abt = 0;
+	vcpu->arch.ctxt.spsr_und = 0;
+	vcpu->arch.ctxt.spsr_irq = 0;
+	vcpu->arch.ctxt.spsr_fiq = 0;
 	vcpu_gp_regs(vcpu)->pstate = pstate;
 
 	/* Reset system registers */
-- 
2.30.2