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guest_linux.go
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guest_linux.go
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//go:build linux
package ivshmem
import (
"fmt"
"os"
"sort"
"strconv"
"strings"
"golang.org/x/sys/unix"
)
const (
PCI_PATH = "/sys/bus/pci/devices"
IVSHMEM_VENDOR = "0x1af4" // Red Hat, Inc.
IVSHMEM_DEVICE = "0x1110" // Inter-VM shared memory
)
// ListDevices lists the available ivshmem devices by their locations. The devices are identified by their vendor and device ids.
func ListDevices() ([]PCILocation, error) {
devices, err := listIvshmemPCIRaw()
if err != nil {
return nil, fmt.Errorf("get raw devices: %w", err)
}
result := make([]PCILocation, 0)
for _, dev := range devices {
loc, err := convertLocation(dev)
if err != nil {
fmt.Println(err)
continue
}
result = append(result, *loc)
}
// Sort by bus -> device -> function
sort.Slice(result, func(a, b int) bool {
if result[a].bus < result[b].bus {
return true
} else if result[a].bus > result[b].bus {
return false
}
if result[a].device < result[b].device {
return true
} else if result[a].device > result[b].device {
return false
}
if result[a].function < result[b].function {
return true
} else if result[a].function > result[b].function {
return false
}
return true
})
return result, nil
}
// convertLocation converts the PCI folder name to a PCILocation (for example "0000:08:00.0").
func convertLocation(locationDescription string) (*PCILocation, error) {
parts := strings.Split(locationDescription, ":")
if len(parts) != 3 {
return nil, fmt.Errorf("invalid location description: %s", locationDescription)
}
bus, err := strconv.ParseUint(parts[1], 16, 8)
if err != nil {
return nil, fmt.Errorf("parse bus: %w", err)
}
devFunc := strings.Split(parts[2], ".")
if len(devFunc) != 2 {
return nil, fmt.Errorf("invalid device/function description: %s", devFunc)
}
device, err := strconv.ParseUint(devFunc[0], 16, 8)
if err != nil {
return nil, fmt.Errorf("parse device: %w", err)
}
function, err := strconv.ParseUint(devFunc[1], 16, 8)
if err != nil {
return nil, fmt.Errorf("parse function: %w", err)
}
return &PCILocation{
bus: uint8(bus),
device: uint8(device),
function: uint8(function),
}, nil
}
// Guest allows to map a shared memory region.
type Guest struct {
loc PCILocation
devPath string
mapped bool
sharedMem []byte
size uint64
}
// NewGuest returns a new Guest based on the PCI location.
func NewGuest(location PCILocation) (*Guest, error) {
devices, err := listIvshmemPCIRaw()
if err != nil {
return nil, fmt.Errorf("get raw devices: %w", err)
}
var found bool
var idx = -1
for i, dev := range devices {
loc, err := convertLocation(dev)
if err != nil {
return nil, fmt.Errorf("convert location: %w", err)
}
if *loc == location {
found = true
idx = i
}
}
if !found {
return nil, ErrCannotFindDevice
}
path := fmt.Sprintf("%s/%s/%s", PCI_PATH, devices[idx], "resource2")
return &Guest{
loc: location,
devPath: path,
}, nil
}
// Map maps the memory into the program address space.
func (g *Guest) Map() error {
if g.mapped {
return ErrAlreadyMapped
}
stat, err := os.Stat(g.devPath)
if err != nil {
return fmt.Errorf("get size: %w", err)
}
file, err := os.OpenFile(g.devPath, os.O_RDWR, 0o600)
if err != nil {
return fmt.Errorf("open device file: %w", err)
}
defer file.Close()
sharedMem, err := unix.Mmap(int(file.Fd()), 0, int(stat.Size()), unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED)
if err != nil {
return fmt.Errorf("mmap: %w", err)
}
g.sharedMem = sharedMem
g.size = uint64(stat.Size())
g.mapped = true
return nil
}
// Unmap unmaps the memory.
func (g Guest) Unmap() error {
if !g.mapped {
return ErrAlreadyUnmapped
}
if err := unix.Munmap(g.sharedMem); err != nil {
return fmt.Errorf("munmap: %w", err)
}
g.mapped = false
return nil
}
// System returns the guest system type.
func (g Guest) System() string {
return "Linux"
}
// Size returns the shared memory size in bytes.
func (g Guest) Size() uint64 {
return g.size
}
// DevPath returns the device path.
func (g Guest) DevPath() string {
return g.devPath
}
// SharedMem returns the shared memory region. Panics if the shared memory isn't mapped yet.
func (g Guest) SharedMem() []byte {
if !g.mapped {
panic("tried to access unmapped memory")
}
return g.sharedMem
}
// Location returns the PCI location of the device.
func (g Guest) Location() PCILocation {
return g.loc
}
// Sync makes sure the changes made to the shared memory are synced.
func (g Guest) Sync() error {
return unix.Msync(g.sharedMem, unix.MS_SYNC)
}
// listIvshmemPCIRaw returns the ivshmem PCI names as seen in PCI_PATH.
func listIvshmemPCIRaw() ([]string, error) {
entry, err := os.ReadDir(PCI_PATH)
if err != nil {
return nil, fmt.Errorf("read pci dir: %w", err)
}
devices := make([]string, 0)
for _, test := range entry {
if len(test.Name()) == 12 && len(strings.Split(test.Name(), ":")) == 3 {
devices = append(devices, test.Name())
}
}
ivshmemDevices := make([]string, 0)
for _, dev := range devices {
data, err := os.ReadFile(fmt.Sprintf("%s/%s/%s", PCI_PATH, dev, "vendor"))
if err != nil {
return nil, fmt.Errorf("vendor read: %w", err)
}
vendorName := strings.TrimSpace(string(data))
if vendorName != IVSHMEM_VENDOR {
continue
}
data, err = os.ReadFile(fmt.Sprintf("%s/%s/%s", PCI_PATH, dev, "device"))
if err != nil {
return nil, fmt.Errorf("device read: %w", err)
}
deviceName := strings.TrimSpace(string(data))
if deviceName != IVSHMEM_DEVICE {
continue
}
ivshmemDevices = append(ivshmemDevices, dev)
}
return ivshmemDevices, nil
}