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

[Yifei Jiang]

Signed-off-by: Yifei Jiang <jiangyi...@huawei.com>
Signed-off-by: Mingwang Li <limingw...@huawei.com>
---
 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