[RFC 2/2] RISC-V: KVM: read\write kernel mmio device support

[Yifei Jiang <jiangyifei@xxxxxxxxxx>]

Signed-off-by: Yifei Jiang <jiangyifei@xxxxxxxxxx>
Signed-off-by: Mingwang Li <limingwang@xxxxxxxxxx>
---
 arch/riscv/kvm/vcpu_exit.c | 38 ++++++++++++++++++++++++++++++++------
 1 file changed, 32 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
index e97ba96cb0ae..448f11179fa8 100644
--- a/arch/riscv/kvm/vcpu_exit.c
+++ b/arch/riscv/kvm/vcpu_exit.c
@@ -191,6 +191,8 @@ static int virtual_inst_fault(struct kvm_vcpu *vcpu, struct kvm_run *run,
 static int emulate_load(struct kvm_vcpu *vcpu, struct kvm_run *run,
 			unsigned long fault_addr, unsigned long htinst)
 {
+	int ret;
+	u8 data_buf[8];
 	unsigned long insn;
 	int shift = 0, len = 0;
 	struct kvm_cpu_trap utrap = { 0 };
@@ -272,19 +274,32 @@ static int emulate_load(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	vcpu->arch.mmio_decode.len = len;
 	vcpu->arch.mmio_decode.return_handled = 0;
 
-	/* Exit to userspace for MMIO emulation */
-	vcpu->stat.mmio_exit_user++;
-	run->exit_reason = KVM_EXIT_MMIO;
+	ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, fault_addr, len,
+						  data_buf);
+
 	run->mmio.is_write = false;
 	run->mmio.phys_addr = fault_addr;
 	run->mmio.len = len;
 
+	if (!ret) {
+		/* We handled the access successfully in the kernel. */
+		memcpy(run->mmio.data, data_buf, len);
+		vcpu->stat.mmio_exit_kernel++;
+		kvm_riscv_vcpu_mmio_return(vcpu, run);
+		return 1;
+	}
+
+	/* Exit to userspace for MMIO emulation */
+	vcpu->stat.mmio_exit_user++;
+	run->exit_reason = KVM_EXIT_MMIO;
+
 	return 0;
 }
 
 static int emulate_store(struct kvm_vcpu *vcpu, struct kvm_run *run,
 			 unsigned long fault_addr, unsigned long htinst)
 {
+	int ret;
 	u8 data8;
 	u16 data16;
 	u32 data32;
@@ -378,13 +393,24 @@ static int emulate_store(struct kvm_vcpu *vcpu, struct kvm_run *run,
 		return -ENOTSUPP;
 	};
 
-	/* Exit to userspace for MMIO emulation */
-	vcpu->stat.mmio_exit_user++;
-	run->exit_reason = KVM_EXIT_MMIO;
+	ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, fault_addr, len,
+						   run->mmio.data);
+
 	run->mmio.is_write = true;
 	run->mmio.phys_addr = fault_addr;
 	run->mmio.len = len;
 
+	if (!ret) {
+		/* We handled the access successfully in the kernel. */
+		vcpu->stat.mmio_exit_kernel++;
+		kvm_riscv_vcpu_mmio_return(vcpu, run);
+		return 1;
+	}
+
+	/* Exit to userspace for MMIO emulation */
+	vcpu->stat.mmio_exit_user++;
+	run->exit_reason = KVM_EXIT_MMIO;
+
 	return 0;
 }
 
-- 
2.19.1