KVM: arm64: Change 32-bit handling of VM system registers

We currently handle 32-bit accesses to trapped VM system registers using
the 32-bit index into the coproc array on the vcpu structure, which is a
union of the coproc array and the sysreg array.

Since all the 32-bit coproc indices are created to correspond to the
architectural mapping between 64-bit system registers and 32-bit
coprocessor registers, and because the AArch64 system registers are the
double in size of the AArch32 coprocessor registers, we can always find
the system register entry that we must update by dividing the 32-bit
coproc index by 2.

This is going to make our lives much easier when we have to start
accessing system registers that use deferred save/restore and might
have to be read directly from the physical CPU.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 15 insertions, 5 deletions

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 6feb4a2215cb..691f81c31018 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -121,16 +121,26 @@ static bool access_vm_reg(struct kvm_vcpu *vcpu,
 			  const struct sys_reg_desc *r)
 {
 	bool was_enabled = vcpu_has_cache_enabled(vcpu);
+	u64 val;
+	int reg = r->reg;
 
 	BUG_ON(!p->is_write);
 
-	if (!p->is_aarch32) {
-		vcpu_sys_reg(vcpu, r->reg) = p->regval;
+	/* See the 32bit mapping in kvm_host.h */
+	if (p->is_aarch32)
+		reg = r->reg / 2;
+
+	if (!p->is_aarch32 || !p->is_32bit) {
+		val = p->regval;
 	} else {
-		if (!p->is_32bit)
-			vcpu_cp15_64_high(vcpu, r->reg) = upper_32_bits(p->regval);
-		vcpu_cp15_64_low(vcpu, r->reg) = lower_32_bits(p->regval);
+		val = vcpu_sys_reg(vcpu, reg);
+		if (r->reg % 2)
+			val = (p->regval << 32) | (u64)lower_32_bits(val);
+		else
+			val = ((u64)upper_32_bits(val) << 32) |
+				lower_32_bits(p->regval);
 	}
+	vcpu_sys_reg(vcpu, reg) = val;
 
 	kvm_toggle_cache(vcpu, was_enabled);
 	return true;