MIPS; KVM: Convert exception entry to uasm

Convert the whole of locore.S (assembly to enter guest and handle
exception entry) to be generated dynamically with uasm. This is done
with minimal changes to the resulting code.

The main changes are:
- Some constants are generated by uasm using LUI+ADDIU instead of
  LUI+ORI.
- Loading of lo and hi are swapped around in vcpu_run but not when
  resuming the guest after an exit. Both bits of logic are now generated
  by the same code.
- Register MOVEs in uasm use different ADDU operand ordering to GNU as,
  putting zero register into rs instead of rt.
- The JALR.HB to call the C exit handler is switched to JALR, since the
  hazard barrier would appear to be unnecessary.

This will allow further optimisation in the future to dynamically handle
the capabilities of the CPU.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim KrÄmář <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/include/asm/kvm_host.h

@@ -533,8 +533,12 @@ int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks);
 /* Debug: dump vcpu state */
 int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu);
 
-/* Trampoline ASM routine to start running in "Guest" context */
-extern int __kvm_mips_vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu);
+extern int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu);
+
+/* Building of entry/exception code */
+void *kvm_mips_build_vcpu_run(void *addr);
+void *kvm_mips_build_exception(void *addr);
+void *kvm_mips_build_exit(void *addr);
 
 /* FPU/MSA context management */
 void __kvm_save_fpu(struct kvm_vcpu_arch *vcpu);

arch/mips/kvm/Kconfig

@@ -17,6 +17,7 @@ if VIRTUALIZATION
 config KVM
 	tristate "Kernel-based Virtual Machine (KVM) support"
 	depends on HAVE_KVM
+	select EXPORT_UASM
 	select PREEMPT_NOTIFIERS
 	select ANON_INODES
 	select KVM_MMIO

arch/mips/kvm/Makefile

@@ -7,7 +7,7 @@ EXTRA_CFLAGS += -Ivirt/kvm -Iarch/mips/kvm
 
 common-objs-$(CONFIG_CPU_HAS_MSA) += msa.o
 
-kvm-objs := $(common-objs-y) mips.o emulate.o locore.o \
+kvm-objs := $(common-objs-y) mips.o emulate.o entry.o \
 	    interrupt.o stats.o commpage.o \
 	    dyntrans.o trap_emul.o fpu.o
 kvm-objs += mmu.o

arch/mips/kvm/interrupt.h

@@ -28,10 +28,6 @@
 #define MIPS_EXC_MAX                12
 /* XXXSL More to follow */
 
-extern char __kvm_mips_vcpu_run_end[];
-extern char mips32_exception[], mips32_exceptionEnd[];
-extern char mips32_GuestException[], mips32_GuestExceptionEnd[];
-
 #define C_TI        (_ULCAST_(1) << 30)
 
 #define KVM_MIPS_IRQ_DELIVER_ALL_AT_ONCE (0)

arch/mips/kvm/mips.c

@@ -247,8 +247,8 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
 
 struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
 {
-	int err, size, offset;
-	void *gebase;
+	int err, size;
+	void *gebase, *p;
 	int i;
 
 	struct kvm_vcpu *vcpu = kzalloc(sizeof(struct kvm_vcpu), GFP_KERNEL);
@@ -286,41 +286,28 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
 	/* Save new ebase */
 	vcpu->arch.guest_ebase = gebase;
 
-	/* Copy L1 Guest Exception handler to correct offset */
+	/* Build guest exception vectors dynamically in unmapped memory */
 
 	/* TLB Refill, EXL = 0 */
-	memcpy(gebase, mips32_exception,
-	       mips32_exceptionEnd - mips32_exception);
+	kvm_mips_build_exception(gebase);
 
 	/* General Exception Entry point */
-	memcpy(gebase + 0x180, mips32_exception,
-	       mips32_exceptionEnd - mips32_exception);
+	kvm_mips_build_exception(gebase + 0x180);
 
 	/* For vectored interrupts poke the exception code @ all offsets 0-7 */
 	for (i = 0; i < 8; i++) {
 		kvm_debug("L1 Vectored handler @ %p\n",
 			  gebase + 0x200 + (i * VECTORSPACING));
-		memcpy(gebase + 0x200 + (i * VECTORSPACING), mips32_exception,
-		       mips32_exceptionEnd - mips32_exception);
+		kvm_mips_build_exception(gebase + 0x200 + i * VECTORSPACING);
 	}
 
-	/* General handler, relocate to unmapped space for sanity's sake */
-	offset = 0x2000;
-	kvm_debug("Installing KVM Exception handlers @ %p, %#x bytes\n",
-		  gebase + offset,
-		  mips32_GuestExceptionEnd - mips32_GuestException);
+	/* General exit handler */
+	p = gebase + 0x2000;
+	p = kvm_mips_build_exit(p);
 
-	memcpy(gebase + offset, mips32_GuestException,
-	       mips32_GuestExceptionEnd - mips32_GuestException);
-
-#ifdef MODULE
-	offset += mips32_GuestExceptionEnd - mips32_GuestException;
-	memcpy(gebase + offset, (char *)__kvm_mips_vcpu_run,
-	       __kvm_mips_vcpu_run_end - (char *)__kvm_mips_vcpu_run);
-	vcpu->arch.vcpu_run = gebase + offset;
-#else
-	vcpu->arch.vcpu_run = __kvm_mips_vcpu_run;
-#endif
+	/* Guest entry routine */
+	vcpu->arch.vcpu_run = p;
+	p = kvm_mips_build_vcpu_run(p);
 
 	/* Invalidate the icache for these ranges */
 	local_flush_icache_range((unsigned long)gebase,