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GNU Guix consists of Scheme code that implements the deployment model
of the Nix package management tool.  In fact, it currently talks to a
build daemon whose code comes from Nix (see the manual for details.)

Nix was initially written by Eelco Dolstra; other people have been
contributing to it.  See `nix/AUTHORS' for details.

The list of GNU Guix contributors is now generated from the output of
'git log' and written to this file, as can be seen in release tarballs.

generated by cgit

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2016 Christine Lemmer-Webber <cwebber@dustycloud.org>
;;; Copyright © 2016, 2017 Leo Famulari <leo@famulari.name>
;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
;;; Copyright © 2017 Marius Bakke <mbakke@fastmail.com>
;;; Copyright © 2018 Chris Marusich <cmmarusich@gmail.com>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (gnu system vm)
  #:use-module (guix config)
  #:use-module (guix store)
  #:use-module (guix gexp)
  #:use-module (guix derivations)
  #:use-module (guix packages)
  #:use-module (guix monads)
  #:use-module (guix records)
  #:use-module (guix modules)
  #:use-module (guix utils)
  #:use-module (gcrypt hash)
  #:use-module (guix base32)
  #:use-module ((guix self) #:select (make-config.scm))

  #:use-module ((gnu build marionette)
                #:select (qemu-command))
  #:use-module (gnu packages base)
  #:use-module (gnu packages bootloaders)
  #:use-module (gnu packages cdrom)
  #:use-module (gnu packages compression)
  #:use-module (gnu packages guile)
  #:autoload   (gnu packages gnupg) (guile-gcrypt)
  #:use-module (gnu packages gawk)
  #:use-module (gnu packages bash)
  #:use-module (gnu packages virtualization)
  #:use-module (gnu packages disk)
  #:use-module (gnu packages linux)

  #:use-module (gnu bootloader)
  #:use-module (gnu bootloader grub)
  #:use-module (gnu image)
  #:use-module (gnu system image)
  #:use-module (gnu system linux-container)
  #:use-module (gnu system linux-initrd)
  #:use-module (gnu bootloader)
  #:use-module (gnu system file-systems)
  #:use-module (gnu system)
  #:use-module (gnu services)
  #:use-module (gnu services base)
  #:use-module (gnu system uuid)

  #:use-module ((srfi srfi-1) #:hide (partition))
  #:use-module (srfi srfi-26)
  #:use-module (rnrs bytevectors)
  #:use-module (ice-9 match)

  #:export (virtualized-operating-system
            system-qemu-image/shared-store-script

            virtual-machine
            virtual-machine?))


;;; Commentary:
;;;
;;; Tools to evaluate build expressions within virtual machines.
;;;
;;; Code:

;; By default, the msize value is 8 KiB, which according to QEMU is
;; insufficient and would degrade performance.  The msize value should roughly
;; match the bandwidth of the system's IO (see:
;; https://wiki.qemu.org/Documentation/9psetup#msize).  Use 100 MiB as a
;; conservative default.
(define %default-msize-value (* 100 (expt 2 20))) ;100 MiB

(define %linux-vm-file-systems
  ;; File systems mounted for 'derivation-in-linux-vm'.  These are shared with
  ;; the host over 9p.
  ;;
  ;; The 9p documentation says that cache=loose is "intended for exclusive,
  ;; read-only mounts", without additional details.  It's much faster than the
  ;; default cache=none, especially when copying and registering store items.
  ;; Thus, use cache=loose, except for /xchg where we want to ensure
  ;; consistency.
  (list (file-system
          (mount-point (%store-prefix))
          (device "store")
          (type "9p")
          (needed-for-boot? #t)
          (flags '(read-only))
          (options (format #f "trans=virtio,cache=loose,msize=~a"
                           %default-msize-value))
          (check? #f))
        (file-system
          (mount-point "/xchg")
          (device "xchg")
          (type "9p")
          (needed-for-boot? #t)
          (options (format #f "trans=virtio,msize=~a" %default-msize-value))
          (check? #f))
        (file-system
          (mount-point "/tmp")
          (device "tmp")
          (type "9p")
          (needed-for-boot? #t)
          (options (format #f "trans=virtio,cache=loose,msize=~a"
                           %default-msize-value))
          (check? #f))))


;;;
;;; VMs that share file systems with the host.
;;;

(define (file-system->mount-tag fs)
  "Return a 9p mount tag for host file system FS."
  ;; QEMU mount tags must be ASCII, at most 31-byte long, cannot contain
  ;; slashes, and cannot start with '_'.  Compute an identifier that
  ;; corresponds to the rules.
  (string-append "TAG"
                 (string-drop (bytevector->base32-string
                               (sha1 (string->utf8 fs)))
                              4)))

(define (mapping->file-system mapping)
  "Return a 9p file system that realizes MAPPING."
  (match mapping
    (($ <file-system-mapping> source target writable?)
     (file-system
       (mount-point target)
       (device (file-system->mount-tag source))
       (type "9p")
       (flags (if writable? '() '(read-only)))
       (options (string-append "trans=virtio"
                               (if writable? "" ",cache=loose")
                               ",msize=" (number->string %default-msize-value)))
       (check? #f)
       (create-mount-point? #t)))))

(define* (virtualized-operating-system os mappings
                                       #:key (full-boot? #f) volatile?)
  "Return an operating system based on OS suitable for use in a virtualized
environment with the store shared with the host.  MAPPINGS is a list of
<file-system-mapping> to realize in the virtualized OS."
  (define user-file-systems
    ;; Remove file systems that conflict with those added below, or that are
    ;; normally bound to real devices.
    (remove (lambda (fs)
              (let ((target (file-system-mount-point fs))
                    (source (file-system-device fs)))
                (or (string=? target (%store-prefix))
                    (string=? target "/")
                    (and (string? source)
                         (string-prefix? "/dev/" source))

                    ;; Labels and UUIDs are necessarily invalid in the VM.
                    (and (file-system-mount? fs)
                         (or (file-system-label? source)
                             (uuid? source))))))
            (operating-system-file-systems os)))

  (define virtual-file-systems
    (cons (file-system
            (mount-point "/")
            (device "/dev/vda1")
            (type "ext4"))

          (append (map mapping->file-system mappings)
                  user-file-systems)))

  (operating-system (inherit os)

    ;; XXX: Until we run QEMU with UEFI support (with the OVMF firmware),
    ;; force the traditional i386/BIOS method.
    ;; See <https://bugs.gnu.org/28768>.
    (bootloader (bootloader-configuration
                  (inherit (operating-system-bootloader os))
                  (bootloader grub-bootloader)
                  (targets '("/dev/vda"))))

    (initrd (lambda (file-systems . rest)
              (apply (operating-system-initrd os)
                     file-systems
                     #:volatile-root? volatile?
                     rest)))

    ;; Disable swap.
    (swap-devices '())

    ;; XXX: When FULL-BOOT? is true, do not add a 9p mount for /gnu/store
    ;; since that would lead the bootloader config to look for the kernel and
    ;; initrd in it.
    (file-systems (if full-boot?
                      virtual-file-systems
                      (cons
                       (file-system
                         (inherit (mapping->file-system %store-mapping))
                         (needed-for-boot? #t))
                       virtual-file-systems)))))

(define* (common-qemu-options image shared-fs
                              #:key rw-image?)
  "Return the a string-value gexp with the common QEMU options to boot IMAGE,
with '-virtfs' options for the host file systems listed in SHARED-FS."

  (define (virtfs-option fs)
    #~(format #f "-virtfs local,path=~s,security_model=none,mount_tag=~s"
              #$fs #$(file-system->mount-tag fs)))

  #~(;; Only enable kvm if we see /dev/kvm exists.
     ;; This allows users without hardware virtualization to still use these
     ;; commands.
     #$@(if (file-exists? "/dev/kvm")
            '("-enable-kvm")
            '())

     "-no-reboot"
     "-object" "rng-random,filename=/dev/urandom,id=guix-vm-rng"
     "-device" "virtio-rng-pci,rng=guix-vm-rng"

     #$@(map virtfs-option shared-fs)
     #$@(if rw-image?
            #~((format #f "-drive file=~a,if=virtio" #$image))
            #~((format #f "-drive file=~a,if=virtio,cache=writeback,werror=report,readonly=on"
                       #$image)))))

(define* (system-qemu-image/shared-store-script os
                                                #:key
                                                (system (%current-system))
                                                (target (%current-target-system))
                                                (qemu qemu)
                                                (graphic? #t)
                                                (volatile? #t)
                                                (memory-size 512)
                                                (mappings '())
                                                full-boot?
                                                (disk-image-size
                                                 (* (if full-boot? 500 70)
                                                    (expt 2 20)))
                                                (options '()))
  "Return a derivation that builds a script to run a virtual machine image of
OS that shares its store with the host.  The virtual machine runs with
MEMORY-SIZE MiB of memory.

MAPPINGS is a list of <file-system-mapping> specifying mapping of host file
systems into the guest.

When FULL-BOOT? is true, the returned script runs everything starting from the
bootloader; otherwise it directly starts the operating system kernel.  When
VOLATILE? is true, an overlay is created on top of a read-only
storage. Otherwise the storage is made persistent.  The DISK-IMAGE-SIZE
parameter specifies the size in bytes of the root disk image; it is mostly
useful when FULL-BOOT?  is true."
  (mlet* %store-monad ((os ->  (virtualized-operating-system
                                os mappings
                                #:full-boot? full-boot?
                                #:volatile? volatile?))
                       (base-image -> (system-image
                                       (image
                                        (inherit
                                         (raw-with-offset-disk-image))
                                        (operating-system os)
                                        (size disk-image-size)
                                        (shared-store?
                                         (and (not full-boot?) volatile?))
                                        (volatile-root? volatile?)))))
    (define kernel-arguments
      #~(list #$@(if graphic? #~() #~("console=ttyS0"))
              #+@(operating-system-kernel-arguments os "/dev/vda1")))

    (define rw-image
      #~(format #f "/tmp/guix-image-~a" (basename #$base-image)))

    (define qemu-exec
      #~(list #+(file-append qemu "/bin/"
                             (qemu-command (or target system)))
              ;; Tells qemu to use the terminal it was started in for IO.
              #$@(if graphic? '() #~("-nographic"))
              #$@(if full-boot?
                     #~()
                     #~("-kernel" #$(operating-system-kernel-file os)
                        "-initrd" #$(file-append os "/initrd")
                        (format #f "-append ~s"
                                (string-join #$kernel-arguments " "))))
              #$@(common-qemu-options (if volatile? base-image rw-image)
                                      (map file-system-mapping-source
                                           (cons %store-mapping mappings))
                                      #:rw-image? (not volatile?))
              "-m " (number->string #$memory-size)
              #$@options))

    (define builder
      #~(call-with-output-file #$output
          (lambda (port)
            (format port "#!~a~%"
                    #+(file-append bash "/bin/sh"))
            (when (not #$volatile?)
              (format port "~a~%"
                      #$(program-file "copy-image"
                                      #~(unless (file-exists? #$rw-image)
                                          (copy-file #$base-image #$rw-image)
                                          (chmod #$rw-image #o640)))))
            (format port "exec ~a \"$@\"~%"
                    (string-join #$qemu-exec " "))
            (chmod port #o555))))

    (gexp->derivation "run-vm.sh" builder)))


;;;
;;; High-level abstraction.
;;;

(define-record-type* <virtual-machine> %virtual-machine
  make-virtual-machine
  virtual-machine?
  (operating-system virtual-machine-operating-system) ;<operating-system>
  (qemu             virtual-machine-qemu              ;<package>
                    (default qemu-minimal))
  (volatile?        virtual-machine-volatile?    ;Boolean
                    (default #t))
  (graphic?         virtual-machine-graphic?      ;Boolean
                    (default #f))
  (memory-size      virtual-machine-memory-size   ;integer (MiB)
                    (default 256))
  (disk-image-size  virtual-machine-disk-image-size   ;integer (bytes)
                    (default 'guess))
  (port-forwardings virtual-machine-port-forwardings ;list of integer pairs
                    (default '())))

(define-syntax virtual-machine
  (syntax-rules ()
    "Declare a virtual machine running the specified OS, with the given
options."
    ((_ os)                                       ;shortcut
     (%virtual-machine (operating-system os)))
    ((_ fields ...)
     (%virtual-machine fields ...))))

(define (port-forwardings->qemu-options forwardings)
  "Return the QEMU option for the given port FORWARDINGS as a string, where
FORWARDINGS is a list of host-port/guest-port pairs."
  (string-join
   (map (match-lambda
          ((host-port . guest-port)
           (string-append "hostfwd=tcp::"
                          (number->string host-port)
                          "-:" (number->string guest-port))))
        forwardings)
   ","))

(define-gexp-compiler (virtual-machine-compiler (vm <virtual-machine>)
                                                system target)
  (match vm
    (($ <virtual-machine> os qemu volatile? graphic? memory-size
                          disk-image-size ())
     (system-qemu-image/shared-store-script os
                                            #:system system
                                            #:target target
                                            #:qemu qemu
                                            #:graphic? graphic?
                                            #:volatile? volatile?
                                            #:memory-size memory-size
                                            #:disk-image-size
                                            disk-image-size))
    (($ <virtual-machine> os qemu volatile? graphic? memory-size
                          disk-image-size forwardings)
     (let ((options
            `("-nic" ,(string-append
                       "user,model=virtio-net-pci,"
                       (port-forwardings->qemu-options forwardings)))))
       (system-qemu-image/shared-store-script os
                                              #:system system
                                              #:target target
                                              #:qemu qemu
                                              #:graphic? graphic?
                                              #:volatile? volatile?
                                              #:memory-size memory-size
                                              #:disk-image-size
                                              disk-image-size
                                              #:options options)))))

;;; vm.scm ends here