KVM: MIPS: Enable KVM support for Loongson-3

This patch enable KVM support for Loongson-3 by selecting HAVE_KVM, but
only enable KVM/VZ on Loongson-3A R4+ (because VZ of early processors
are incomplete). Besides, Loongson-3 support SMP guests, so we clear the
linked load bit of LLAddr in kvm_vz_vcpu_load() if the guest has more
than one VCPUs.

Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
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: <1590220602-3547-15-git-send-email-chenhc@lemote.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/Kconfig

@@ -1404,6 +1404,7 @@ config CPU_LOONGSON64
 	select MIPS_L1_CACHE_SHIFT_6
 	select GPIOLIB
 	select SWIOTLB
+	select HAVE_KVM
 	help
 		The Loongson GSx64(GS264/GS464/GS464E/GS464V) series of processor
 		cores implements the MIPS64R2 instruction set with many extensions,

arch/mips/kernel/cpu-probe.c

@@ -2076,6 +2076,7 @@ static inline void cpu_probe_loongson(struct cpuinfo_mips *c, unsigned int cpu)
 		c->writecombine = _CACHE_UNCACHED_ACCELERATED;
 		c->ases |= (MIPS_ASE_LOONGSON_MMI | MIPS_ASE_LOONGSON_CAM |
 			MIPS_ASE_LOONGSON_EXT | MIPS_ASE_LOONGSON_EXT2);
+		c->ases &= ~MIPS_ASE_VZ; /* VZ of Loongson-3A2000/3000 is incomplete */
 		break;
 	case PRID_IMP_LOONGSON_64G:
 		c->cputype = CPU_LOONGSON64;

arch/mips/kvm/vz.c

@@ -2697,7 +2697,7 @@ static int kvm_vz_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	 * prevents a SC on the next VCPU from succeeding by matching a LL on
 	 * the previous VCPU.
 	 */
-	if (cpu_guest_has_rw_llb)
+	if (vcpu->kvm->created_vcpus > 1)
 		write_gc0_lladdr(0);
 
 	return 0;