+/**
+ * kvm_mips_entry_setup() - Perform global setup for entry code.
+ *
+ * Perform global setup for entry code, such as choosing a scratch register.
+ *
+ * Returns: 0 on success.
+ * -errno on failure.
+ */
+int kvm_mips_entry_setup(void)
+{
+ /*
+ * We prefer to use KScratchN registers if they are available over the
+ * defaults above, which may not work on all cores.
+ */
+ unsigned int kscratch_mask = cpu_data[0].kscratch_mask & 0xfc;
+
+ /* Pick a scratch register for storing VCPU */
+ if (kscratch_mask) {
+ scratch_vcpu[0] = 31;
+ scratch_vcpu[1] = ffs(kscratch_mask) - 1;
+ kscratch_mask &= ~BIT(scratch_vcpu[1]);
+ }
+
+ /* Pick a scratch register to use as a temp for saving state */
+ if (kscratch_mask) {
+ scratch_tmp[0] = 31;
+ scratch_tmp[1] = ffs(kscratch_mask) - 1;
+ kscratch_mask &= ~BIT(scratch_tmp[1]);
+ }
+
+ return 0;
+}
+
+static void kvm_mips_build_save_scratch(u32 **p, unsigned int tmp,
+ unsigned int frame)
+{
+ /* Save the VCPU scratch register value in cp0_epc of the stack frame */
+ uasm_i_mfc0(p, tmp, scratch_vcpu[0], scratch_vcpu[1]);
+ UASM_i_SW(p, tmp, offsetof(struct pt_regs, cp0_epc), frame);
+
+ /* Save the temp scratch register value in cp0_cause of stack frame */
+ if (scratch_tmp[0] == 31) {
+ uasm_i_mfc0(p, tmp, scratch_tmp[0], scratch_tmp[1]);
+ UASM_i_SW(p, tmp, offsetof(struct pt_regs, cp0_cause), frame);
+ }
+}
+
+static void kvm_mips_build_restore_scratch(u32 **p, unsigned int tmp,
+ unsigned int frame)
+{
+ /*
+ * Restore host scratch register values saved by
+ * kvm_mips_build_save_scratch().
+ */
+ UASM_i_LW(p, tmp, offsetof(struct pt_regs, cp0_epc), frame);
+ uasm_i_mtc0(p, tmp, scratch_vcpu[0], scratch_vcpu[1]);
+
+ if (scratch_tmp[0] == 31) {
+ UASM_i_LW(p, tmp, offsetof(struct pt_regs, cp0_cause), frame);
+ uasm_i_mtc0(p, tmp, scratch_tmp[0], scratch_tmp[1]);
+ }
+}
+