KVM: MIPS: Use root tlb to control guest's CCA for Loongson-3

KVM guest has two levels of address translation: guest tlb translates
GVA to GPA, and root tlb translates GPA to HPA. By default guest's CCA
is controlled by guest tlb, but Loongson-3 maintains all cache coherency
by hardware (including multi-core coherency and I/O DMA coherency) so it
prefers all guest mappings be cacheable mappings. Thus, we use root tlb
to control guest's CCA for Loongson-3.
Reviewed-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Co-developed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-Id: <1590220602-3547-8-git-send-email-chenhc@lemote.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/kvm/vz.c

@@ -2871,6 +2871,12 @@ static int kvm_vz_hardware_enable(void)
 	if (cpu_has_guestctl2)
 		clear_c0_guestctl2(0x3f << 10);
 
+#ifdef CONFIG_CPU_LOONGSON64
+	/* Control guest CCA attribute */
+	if (cpu_has_csr())
+		csr_writel(csr_readl(0xffffffec) | 0x1, 0xffffffec);
+#endif
+
 	return 0;
 }