KVM: arm64: Get rid of the AArch32 register mapping code

The only use of the register mapping code was for the sake of the LR
mapping, which we trivially solved in a previous patch. Get rid of
the whole thing now.

Signed-off-by: Marc Zyngier <maz@kernel.org>

1 files changed, 25 insertions, 3 deletions

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index dfb5218137ca..3f23f7478d2a 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -252,10 +252,32 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	memcpy(addr, valp, KVM_REG_SIZE(reg->id));
 
 	if (*vcpu_cpsr(vcpu) & PSR_MODE32_BIT) {
-		int i;
+		int i, nr_reg;
+
+		switch (*vcpu_cpsr(vcpu)) {
+		/*
+		 * Either we are dealing with user mode, and only the
+		 * first 15 registers (+ PC) must be narrowed to 32bit.
+		 * AArch32 r0-r14 conveniently map to AArch64 x0-x14.
+		 */
+		case PSR_AA32_MODE_USR:
+		case PSR_AA32_MODE_SYS:
+			nr_reg = 15;
+			break;
+
+		/*
+		 * Otherwide, this is a priviledged mode, and *all* the
+		 * registers must be narrowed to 32bit.
+		 */
+		default:
+			nr_reg = 31;
+			break;
+		}
+
+		for (i = 0; i < nr_reg; i++)
+			vcpu_set_reg(vcpu, i, (u32)vcpu_get_reg(vcpu, i));
 
-		for (i = 0; i < 16; i++)
-			*vcpu_reg32(vcpu, i) = (u32)*vcpu_reg32(vcpu, i);
+		*vcpu_pc(vcpu) = (u32)*vcpu_pc(vcpu);
 	}
 out:
 	return err;