docs: kvm: convert devices/xics.txt to ReST

- Use title markups;
- adjust indentation and add blank lines as needed;
- adjust tables to match ReST accepted formats;
- use :field: markups.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/virt/kvm/devices/index.rst

@@ -15,3 +15,4 @@ Devices
    vcpu
    vfio
    vm
+   xics

Documentation/virt/kvm/devices/xics.txt → Documentation/virt/kvm/devices/xics.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+=========================
 XICS interrupt controller
+=========================
 
 Device type supported: KVM_DEV_TYPE_XICS
 
 Groups:
   1. KVM_DEV_XICS_GRP_SOURCES
-  Attributes: One per interrupt source, indexed by the source number.
+       Attributes:
 
+         One per interrupt source, indexed by the source number.
   2. KVM_DEV_XICS_GRP_CTRL
-  Attributes:
-    2.1 KVM_DEV_XICS_NR_SERVERS (write only)
+       Attributes:
+
+         2.1 KVM_DEV_XICS_NR_SERVERS (write only)
+
   The kvm_device_attr.addr points to a __u32 value which is the number of
   interrupt server numbers (ie, highest possible vcpu id plus one).
+
   Errors:
-    -EINVAL: Value greater than KVM_MAX_VCPU_ID.
-    -EFAULT: Invalid user pointer for attr->addr.
-    -EBUSY:  A vcpu is already connected to the device.
+
+    =======  ==========================================
+    -EINVAL  Value greater than KVM_MAX_VCPU_ID.
+    -EFAULT  Invalid user pointer for attr->addr.
+    -EBUSY   A vcpu is already connected to the device.
+    =======  ==========================================
 
 This device emulates the XICS (eXternal Interrupt Controller
 Specification) defined in PAPR.  The XICS has a set of interrupt
@@ -53,24 +64,29 @@ the interrupt source number.  The 64 bit state word has the following
 bitfields, starting from the least-significant end of the word:
 
 * Destination (server number), 32 bits
+
   This specifies where the interrupt should be sent, and is the
   interrupt server number specified for the destination vcpu.
 
 * Priority, 8 bits
+
   This is the priority specified for this interrupt source, where 0 is
   the highest priority and 255 is the lowest.  An interrupt with a
   priority of 255 will never be delivered.
 
 * Level sensitive flag, 1 bit
+
   This bit is 1 for a level-sensitive interrupt source, or 0 for
   edge-sensitive (or MSI).
 
 * Masked flag, 1 bit
+
   This bit is set to 1 if the interrupt is masked (cannot be delivered
   regardless of its priority), for example by the ibm,int-off RTAS
   call, or 0 if it is not masked.
 
 * Pending flag, 1 bit
+
   This bit is 1 if the source has a pending interrupt, otherwise 0.
 
 Only one XICS instance may be created per VM.