kconfig: add more help messages to config symbols

Add help messages to all visible symbols except those heap-related ones which
will be dropped eventually.

v2 -> v3

* Fix typos and misleading descriptions.

v1 -> v2

* Per kconfig language, help messages shall have a larger indent level than the
  attributes.
* Rephrase for clarify.

Tracked-On: #1588
Signed-off-by: Junjie Mao <junjie.mao@intel.com>
Reviewed-by: Anthony Xu <anthony.xu@intel.com>

hypervisor/arch/x86/Kconfig

@@ -1,26 +1,43 @@
 choice
 	prompt "Platform"
 	default PLATFORM_SBL
+	help
+	  The BIOS used on the target board.
 
 config PLATFORM_UEFI
 	bool "UEFI"
 	select EFI_STUB
+	help
+	  Select this if the target board uses UEFI.
 
 config PLATFORM_SBL
 	bool "SBL"
+	help
+	  Select this if the target board uses Slim Bootloader.
 
 endchoice
 
 choice
 	prompt "Hypervisor mode"
 	default SHARING_MODE
+	help
+	  Select the usage mode of the hypervisor.
 
 config SHARING_MODE
 	bool "Sharing mode"
+	help
+	  In sharing mode, the first VM (called Service OS or SOS) is capable of
+	  managing the other VMs (called User OS or UOS) and trap/mediate their
+	  I/O accesses to physical devices.
 
 config PARTITION_MODE
 	bool "Partition mode"
 	depends on PLATFORM_SBL
+	help
+	  In partition mode, every VM owns part of the physical resources
+	  exclusively and runs with minimal interference from the others. The VM
+	  configurations are statically defined in the source.
+
 endchoice
 
 config PLATFORM
@@ -31,16 +48,27 @@ config PLATFORM
 config RELEASE
 	bool "Release build"
 	default n
+	help
+	  Whether to build a release version of the hypervisor. Logs, serial
+	  console and hypervisor shell are available only in non-release
+	  (i.e. debug) builds. Assertions are not effective in release builds.
 
 config MAX_VM_NUM
 	int "Maximum number of VM"
 	range 1 8
 	default 4
+	help
+	  The maximum number of virtual machines (VMs) the hypervisor can
+	  support.  This is customizable per the use cases of the build. For
+	  general-purpose builds the maximum of physical cores can be used.
 
 config MAX_VCPUS_PER_VM
 	int "Maximum number of VCPUS per VM"
 	range 1 8
 	default 4
+	help
+	  The maximum number of virtual CPUs the hypervisor can support in a
+	  single VM.
 
 config MAX_PCPU_NUM
 	int "Maximum number of PCPU"
@@ -48,45 +76,56 @@ config MAX_PCPU_NUM
 	default 8
 
 config MAX_IOMMU_NUM
-	int "Maximum number of iommu dev"
+	int "Maximum number of IOMMU devices"
 	range 1 2
 	default 2
+	help
+	  The maximum number of physical IOMMUs the hypervisor can support.
 
 config STACK_SIZE
-	hex "Capacity of each stack used in the hypervisor"
+	hex "Capacity of one stack, in byte"
 	default 0x2000
-
+	help
-config LOG_BUF_SIZE
+	  The size of stacks used by physical cores. Each core uses one stack
-	hex "Capacity of logbuf"
+	  for normal operations and another three for specific exceptions.
-	default 0x100000
 
 config LOG_DESTINATION
 	int "Bitmap of consoles where logs are printed"
 	range 0 7
 	default 7
 	help
-	A bitmap indicating the destinations of log messages. Currently there
+	  A bitmap indicating the destinations of log messages. Currently there
-	are 3 destinations available. Bit 0 represents the serial console, bit
+	  are 3 destinations available. Bit 0 represents the serial console, bit
-	1 the SOS ACRN log and bit 2 NPK log.
+	  1 the SOS ACRN log and bit 2 NPK log. Effective only in debug builds.
 
 config CPU_UP_TIMEOUT
 	int "Timeout in ms when bringing up secondary CPUs"
 	range 100 200
 	default 100
 	help
-	A 32-bit integer specifying the timeout in microsecond when waiting for
+	  A 32-bit integer specifying the timeout in millisecond when waiting
-	secondary CPUs to start up.
+	  for secondary CPUs to start up.
 
 choice
 	prompt "serial IO type"
+	depends on !RELEASE
 	default SERIAL_MMIO if PLATFORM_SBL
 	default SERIAL_PIO  if PLATFORM_UEFI
+	help
+	  Whether the physical serial port shall be accessed via memory-mapped
+	  registers or I/O ports.
 
 config SERIAL_MMIO
 	bool "MMIO"
+	help
+	  Select this if the serial port shall be accessed via memory-mapped
+	  registers.
 
 config SERIAL_PIO
 	bool "PIO"
+	help
+	  Select this if the serial port shall be accessed via in/out
+	  instructions.
 
 endchoice
 
@@ -95,16 +134,16 @@ config SERIAL_MMIO_BASE
 	depends on SERIAL_MMIO
 	default 0xfc000000
 	help
-	A 64-bit integer indicating the base physical address of the
+	  A 64-bit integer indicating the base physical address of the
-	memory-mapped UART registers.
+	  memory-mapped UART registers.
 
 config SERIAL_PIO_BASE
 	hex "Base address of serial PIO region"
 	depends on SERIAL_PIO
 	default 0x3f8
 	help
-	The base of the UART ports. This is logically 16-bit but used as a
+	  The base address of the UART ports. This is logically 16-bit but used
-	64-bit integer.
+	  as a 64-bit integer.
 
 config MALLOC_ALIGN
 	int "Block size in the heap for malloc()"
@@ -121,62 +160,86 @@ config HEAP_SIZE
 
 config CONSOLE_LOGLEVEL_DEFAULT
 	int "Default loglevel on the serial console"
+	depends on !RELEASE
 	range 0 6
 	default 3
+	help
+	  This indicates the maximum debug level of logs that will be available
+	  on the the serial console. The higher the number, the more logs will
+	  be available.
 
 config MEM_LOGLEVEL_DEFAULT
 	int "Default loglevel in memory"
+	depends on !RELEASE
 	range 0 6
 	default 5
+	help
+	  This indicates the maximum debug level of logs that will be available
+	  in the logbuf in memory which can be accessed by ACRN log in SOS. The
+	  higher the number, the more logs will be available.
 
 config NPK_LOGLEVEL_DEFAULT
 	int "Default loglevel for the hypervisor NPK log"
+	depends on !RELEASE
 	range 0 6
 	default 5
+	help
+	  This indicates the maximum debug level of logs that will be available
+	  via NPK log. The higher the number, the more logs will be available.
 
 config LOW_RAM_SIZE
 	hex "Size of the low RAM region"
 	default 0x00010000
 	help
-	A 32-bit integer indicating the size of RAM region below address
+	  A 32-bit integer indicating the size of RAM region below address
-	0x10000, starting from address 0x0.
+	  0x10000, starting from address 0x0.
 
 config RAM_START
 	hex "Address of the RAM region assigned to the hypervisor"
 	default 0x6e000000 if PLATFORM_SBL
 	default 0x00100000 if PLATFORM_UEFI
 	help
-	A 64-bit integer indicating the base address to where the hypervisor
+	  A 64-bit integer indicating the base address to where the hypervisor
-	should be loaded to. If RELOC is disabled the bootloader is required to
+	  should be loaded to. If RELOC is disabled the bootloader is required
-	load the hypervisor to this specific address. Otherwise the hypervisor
+	  to load the hypervisor to this specific address. Otherwise the
-	will not boot.With RELOC enabled the hypervisor is capable of relocating
+	  hypervisor will not boot. With RELOC enabled the hypervisor is capable
-	its symbols to where it is placed at, and thus the bootloader may not
+	  of relocating its symbols to where it is placed at, and thus the
-	place the hypervisor at this specific address.
+	  bootloader may not place the hypervisor at this specific address.
 
 config RAM_SIZE
 	hex "Size of the RAM region assigned to the hypervisor"
 	default 0x02000000
 	help
-	A 64-bit integer indicating the size of RAM assigned to the
+	  A 64-bit integer indicating the size of RAM assigned to the
-	hypervisor. It is ensured at link time that the footprint of the
+	  hypervisor. It is ensured at link time that the footprint of the
-	hypervisor does not exceed this size.
+	  hypervisor does not exceed this size.
 
 config CONSTANT_ACPI
 	bool "The platform ACPI info is constant"
 	default n
+	help
+	  Whether constant ACPI tables shall be used. If selected, the built-in
+	  ACPI tables, usually generated on target platforms by an offline tool,
+	  will be used. If not a fixup subroutine will be invoked to update the
+	  built-in tables after parsing the real ACPI tables at runtime.
 
 config DMAR_PARSE_ENABLED
 	bool
 	default n if PLATFORM_SBL
 	default y if PLATFORM_UEFI
+	help
+	  Whether to parse the ACPI DMA Remapping tables at runtime.
 
 config GPU_SBDF
 	hex
 	depends on DMAR_PARSE_ENABLED
 	default 0x00000010
 	help
-	A 32-bit integer encoding the segment, bus, device and function of the
+	  A 32-bit integer encoding the segment, bus, device and function of the
-	GPU.
+	  GPU. This integer consists of a 16-bit segment ID, 8-bit bus ID, 5-bit
+	  device ID and 3-bit function ID. As an example, for PCI device at
+	  00:02.0 in DRHD segment 0, this SBDF would be (0 << 16) | (0 << 8) |
+	  (2 << 3) | (0 << 0), i.e. 0x00000010.
 
 config EFI_STUB
 	bool
@@ -195,11 +258,19 @@ config MTRR_ENABLED
 config RELOC
 	bool "Enable relocation"
 	default n
+	help
+	  When selected, the hypervisor will relocate itself to where it is
+	  loaded. This allows the bootloader to put the hypervisor image to
+	  wherever appropriate. Without relocation the bootloader must put the
+	  image to RAM_START, otherwise the hypervisor will not start up.
 
 config IOMMU_INIT_BUS_LIMIT
-	hex "bus limitation when iommu init"
+	hex "Limit of PCI bus on IOMMU initialization"
 	default 0xf if PLATFORM_SBL
 	default 0xff if PLATFORM_UEFI
+	help
+	  Any BDF with a bus ID smaller than or equal to this limit is mapped to
+	  the IOMMU domain of the first VM.
 
 config MAX_PCI_DEV_NUM
 	int "Maximum number of PCI dev"