KVM: nVMX: Improve I/O exit handling

This prevents trapping L2 I/O exits if L1 has neither unconditional nor
bitmap-based exiting enabled. Furthermore, it implements I/O bitmap
handling.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 47 insertions, 2 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 6667042714cc..b4ce43c82748 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5908,6 +5908,52 @@ static int (*const kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
 static const int kvm_vmx_max_exit_handlers =
         ARRAY_SIZE(kvm_vmx_exit_handlers);
 
+static bool nested_vmx_exit_handled_io(struct kvm_vcpu *vcpu,
+                                       struct vmcs12 *vmcs12)
+{
+        unsigned long exit_qualification;
+        gpa_t bitmap, last_bitmap;
+        unsigned int port;
+        int size;
+        u8 b;
+
+        if (nested_cpu_has(vmcs12, CPU_BASED_UNCOND_IO_EXITING))
+                return 1;
+
+        if (!nested_cpu_has(vmcs12, CPU_BASED_USE_IO_BITMAPS))
+                return 0;
+
+        exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
+
+        port = exit_qualification >> 16;
+        size = (exit_qualification & 7) + 1;
+
+        last_bitmap = (gpa_t)-1;
+        b = -1;
+
+        while (size > 0) {
+                if (port < 0x8000)
+                        bitmap = vmcs12->io_bitmap_a;
+                else if (port < 0x10000)
+                        bitmap = vmcs12->io_bitmap_b;
+                else
+                        return 1;
+                bitmap += (port & 0x7fff) / 8;
+
+                if (last_bitmap != bitmap)
+                        if (kvm_read_guest(vcpu->kvm, bitmap, &b, 1))
+                                return 1;
+                if (b & (1 << (port & 7)))
+                        return 1;
+
+                port++;
+                size--;
+                last_bitmap = bitmap;
+        }
+
+        return 0;
+}
+
 /*
  * Return 1 if we should exit from L2 to L1 to handle an MSR access access,
  * rather than handle it ourselves in L0. I.e., check whether L1 expressed
@@ -6097,8 +6143,7 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
         case EXIT_REASON_DR_ACCESS:
                 return nested_cpu_has(vmcs12, CPU_BASED_MOV_DR_EXITING);
         case EXIT_REASON_IO_INSTRUCTION:
-                /* TODO: support IO bitmaps */
-                return 1;
+                return nested_vmx_exit_handled_io(vcpu, vmcs12);
         case EXIT_REASON_MSR_READ:
         case EXIT_REASON_MSR_WRITE:
                 return nested_vmx_exit_handled_msr(vcpu, vmcs12, exit_reason);