LoongArch: KVM: Add iocsr and mmio bus simulation in kernel

Add iocsr and mmio memory read and write simulation to the kernel. When
the VM accesses the device address space through iocsr instructions or
mmio, it does not need to return to the qemu user mode but can directly
completes the access in the kernel mode.

Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Xianglai Li <lixianglai@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Author: lixianglai

arch/loongarch/kvm/exit.c

@@ -157,7 +157,7 @@ static int kvm_handle_csr(struct kvm_vcpu *vcpu, larch_inst inst)
 int kvm_emu_iocsr(larch_inst inst, struct kvm_run *run, struct kvm_vcpu *vcpu)
 {
 	int ret;
-	unsigned long val;
+	unsigned long *val;
 	u32 addr, rd, rj, opcode;
 
 	/*
@@ -170,6 +170,7 @@ int kvm_emu_iocsr(larch_inst inst, struct kvm_run *run, struct kvm_vcpu *vcpu)
 	ret = EMULATE_DO_IOCSR;
 	run->iocsr_io.phys_addr = addr;
 	run->iocsr_io.is_write = 0;
+	val = &vcpu->arch.gprs[rd];
 
 	/* LoongArch is Little endian */
 	switch (opcode) {
@@ -202,16 +203,25 @@ int kvm_emu_iocsr(larch_inst inst, struct kvm_run *run, struct kvm_vcpu *vcpu)
 		run->iocsr_io.is_write = 1;
 		break;
 	default:
-		ret = EMULATE_FAIL;
-		break;
+		return EMULATE_FAIL;
 	}
 
-	if (ret == EMULATE_DO_IOCSR) {
-		if (run->iocsr_io.is_write) {
-			val = vcpu->arch.gprs[rd];
-			memcpy(run->iocsr_io.data, &val, run->iocsr_io.len);
-		}
-		vcpu->arch.io_gpr = rd;
+	if (run->iocsr_io.is_write) {
+		if (!kvm_io_bus_write(vcpu, KVM_IOCSR_BUS, addr, run->iocsr_io.len, val))
+			ret = EMULATE_DONE;
+		else
+			/* Save data and let user space to write it */
+			memcpy(run->iocsr_io.data, val, run->iocsr_io.len);
+
+		trace_kvm_iocsr(KVM_TRACE_IOCSR_WRITE, run->iocsr_io.len, addr, val);
+	} else {
+		if (!kvm_io_bus_read(vcpu, KVM_IOCSR_BUS, addr, run->iocsr_io.len, val))
+			ret = EMULATE_DONE;
+		else
+			/* Save register id for iocsr read completion */
+			vcpu->arch.io_gpr = rd;
+
+		trace_kvm_iocsr(KVM_TRACE_IOCSR_READ, run->iocsr_io.len, addr, NULL);
 	}
 
 	return ret;
@@ -447,19 +457,33 @@ int kvm_emu_mmio_read(struct kvm_vcpu *vcpu, larch_inst inst)
 	}
 
 	if (ret == EMULATE_DO_MMIO) {
+		trace_kvm_mmio(KVM_TRACE_MMIO_READ, run->mmio.len, run->mmio.phys_addr, NULL);
+
+		/*
+		 * If mmio device such as PCH-PIC is emulated in KVM,
+		 * it need not return to user space to handle the mmio
+		 * exception.
+		 */
+		ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, vcpu->arch.badv,
+				      run->mmio.len, &vcpu->arch.gprs[rd]);
+		if (!ret) {
+			update_pc(&vcpu->arch);
+			vcpu->mmio_needed = 0;
+			return EMULATE_DONE;
+		}
+
 		/* Set for kvm_complete_mmio_read() use */
 		vcpu->arch.io_gpr = rd;
 		run->mmio.is_write = 0;
 		vcpu->mmio_is_write = 0;
-		trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, run->mmio.len,
-				run->mmio.phys_addr, NULL);
-	} else {
-		kvm_err("Read not supported Inst=0x%08x @%lx BadVaddr:%#lx\n",
-			inst.word, vcpu->arch.pc, vcpu->arch.badv);
-		kvm_arch_vcpu_dump_regs(vcpu);
-		vcpu->mmio_needed = 0;
+		return EMULATE_DO_MMIO;
 	}
 
+	kvm_err("Read not supported Inst=0x%08x @%lx BadVaddr:%#lx\n",
+			inst.word, vcpu->arch.pc, vcpu->arch.badv);
+	kvm_arch_vcpu_dump_regs(vcpu);
+	vcpu->mmio_needed = 0;
+
 	return ret;
 }
 
@@ -600,19 +624,29 @@ int kvm_emu_mmio_write(struct kvm_vcpu *vcpu, larch_inst inst)
 	}
 
 	if (ret == EMULATE_DO_MMIO) {
+		trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, run->mmio.len, run->mmio.phys_addr, data);
+
+		/*
+		 * If mmio device such as PCH-PIC is emulated in KVM,
+		 * it need not return to user space to handle the mmio
+		 * exception.
+		 */
+		ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, vcpu->arch.badv, run->mmio.len, data);
+		if (!ret)
+			return EMULATE_DONE;
+
 		run->mmio.is_write = 1;
 		vcpu->mmio_needed = 1;
 		vcpu->mmio_is_write = 1;
-		trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, run->mmio.len,
-				run->mmio.phys_addr, data);
-	} else {
-		vcpu->arch.pc = curr_pc;
-		kvm_err("Write not supported Inst=0x%08x @%lx BadVaddr:%#lx\n",
-			inst.word, vcpu->arch.pc, vcpu->arch.badv);
-		kvm_arch_vcpu_dump_regs(vcpu);
-		/* Rollback PC if emulation was unsuccessful */
+		return EMULATE_DO_MMIO;
 	}
 
+	vcpu->arch.pc = curr_pc;
+	kvm_err("Write not supported Inst=0x%08x @%lx BadVaddr:%#lx\n",
+			inst.word, vcpu->arch.pc, vcpu->arch.badv);
+	kvm_arch_vcpu_dump_regs(vcpu);
+	/* Rollback PC if emulation was unsuccessful */
+
 	return ret;
 }
 

include/linux/kvm_host.h

@@ -219,6 +219,7 @@ enum kvm_bus {
 	KVM_PIO_BUS,
 	KVM_VIRTIO_CCW_NOTIFY_BUS,
 	KVM_FAST_MMIO_BUS,
+	KVM_IOCSR_BUS,
 	KVM_NR_BUSES
 };
 

include/trace/events/kvm.h

@@ -236,6 +236,41 @@ TRACE_EVENT(kvm_mmio,
 		  __entry->len, __entry->gpa, __entry->val)
 );
 
+#define KVM_TRACE_IOCSR_READ_UNSATISFIED 0
+#define KVM_TRACE_IOCSR_READ 1
+#define KVM_TRACE_IOCSR_WRITE 2
+
+#define kvm_trace_symbol_iocsr \
+	{ KVM_TRACE_IOCSR_READ_UNSATISFIED, "unsatisfied-read" }, \
+	{ KVM_TRACE_IOCSR_READ, "read" }, \
+	{ KVM_TRACE_IOCSR_WRITE, "write" }
+
+TRACE_EVENT(kvm_iocsr,
+	TP_PROTO(int type, int len, u64 gpa, void *val),
+	TP_ARGS(type, len, gpa, val),
+
+	TP_STRUCT__entry(
+		__field(	u32,	type	)
+		__field(	u32,	len	)
+		__field(	u64,	gpa	)
+		__field(	u64,	val	)
+	),
+
+	TP_fast_assign(
+		__entry->type		= type;
+		__entry->len		= len;
+		__entry->gpa		= gpa;
+		__entry->val		= 0;
+		if (val)
+			memcpy(&__entry->val, val,
+			       min_t(u32, sizeof(__entry->val), len));
+	),
+
+	TP_printk("iocsr %s len %u gpa 0x%llx val 0x%llx",
+		  __print_symbolic(__entry->type, kvm_trace_symbol_iocsr),
+		  __entry->len, __entry->gpa, __entry->val)
+);
+
 #define kvm_fpu_load_symbol	\
 	{0, "unload"},		\
 	{1, "load"}