vm: Add (guix build vm) module.

* guix/build/vm.scm: New file.
* Makefile.am (MODULES): Add it.
* gnu/system/vm.scm (expression->derivation-in-linux-vm): Use it.

Makefile.am

@@ -69,6 +69,7 @@ MODULES =					\
   guix/build/pull.scm				\
   guix/build/rpath.scm				\
   guix/build/svn.scm				\
+  guix/build/vm.scm				\
   guix/packages.scm				\
   guix/snix.scm					\
   guix/scripts/download.scm			\

gnu/system/vm.scm

@@ -119,67 +119,27 @@ made available under the /xchg CIFS share."
     ;; Code that launches the VM that evaluates EXP.
     `(let ()
        (use-modules (guix build utils)
-                    (srfi srfi-1)
+                    (guix build vm))
-                    (ice-9 rdelim))
 
-       (let ((out     (assoc-ref %outputs "out"))
+       (let ((linux   (string-append (assoc-ref %build-inputs "linux")
-             (cu      (string-append (assoc-ref %build-inputs "coreutils")
-                                     "/bin"))
-             (qemu    (string-append (assoc-ref %build-inputs "qemu")
-                                     "/bin/qemu-system-"
-                                     (car (string-split ,system #\-))))
-             (img     (string-append (assoc-ref %build-inputs "qemu")
-                                     "/bin/qemu-img"))
-             (linux   (string-append (assoc-ref %build-inputs "linux")
                                      "/bzImage"))
              (initrd  (string-append (assoc-ref %build-inputs "initrd")
                                      "/initrd"))
-             (builder (assoc-ref %build-inputs "builder")))
+             (builder (assoc-ref %build-inputs "builder"))
+             (graphs  ',(match references-graphs
+                          (((graph-files . _) ...) graph-files)
+                          (_ #f))))
 
-         ;; XXX: QEMU uses "rm -rf" when it's done to remove the temporary SMB
+         (set-path-environment-variable "PATH" '("bin")
-         ;; directory, so it really needs `rm' in $PATH.
+                                        (map cdr %build-inputs))
-         (setenv "PATH" cu)
 
-         ,(if make-disk-image?
+         (load-in-linux-vm builder
-              `(zero? (system* img "create" "-f" "qcow2" "image.qcow2"
+                           #:output (assoc-ref %outputs "out")
-                               ,(number->string disk-image-size)))
+                           #:linux linux #:initrd initrd
-              '(begin))
+                           #:memory-size ,memory-size
-
+                           #:make-disk-image? ,make-disk-image?
-         (mkdir "xchg")
+                           #:disk-image-size ,disk-image-size
-
+                           #:references-graphs graphs))))
-         ;; Copy the reference-graph files under xchg/ so EXP can access it.
-         (begin
-           ,@(match references-graphs
-               (((graph-files . _) ...)
-                (map (lambda (file)
-                       `(copy-file ,file
-                                   ,(string-append "xchg/" file)))
-                     graph-files))
-               (#f '())))
-
-         (and (zero?
-               (system* qemu "-enable-kvm" "-nographic" "-no-reboot"
-                        "-m" ,(number->string memory-size)
-                        "-net" "nic,model=virtio"
-                        "-virtfs"
-                        ,(string-append "local,id=store_dev,path=" (%store-prefix)
-                                        ",security_model=none,mount_tag=store")
-                        "-virtfs"
-                        ,(string-append "local,id=xchg_dev,path=xchg"
-                                        ",security_model=none,mount_tag=xchg")
-                        "-kernel" linux
-                        "-initrd" initrd
-                        "-append" (string-append "console=ttyS0 --load="
-                                                 builder)
-                        ,@(if make-disk-image?
-                              '("-hda" "image.qcow2")
-                              '())))
-              ,(if make-disk-image?
-                   '(copy-file "image.qcow2"      ; XXX: who mkdir'd OUT?
-                               out)
-                   '(begin
-                      (mkdir out)
-                      (copy-recursively "xchg" out)))))))
 
   (mlet* %store-monad
       ((input-alist  (sequence %store-monad input-alist))
@@ -206,6 +166,7 @@ made available under the /xchg CIFS share."
                            #:env-vars env-vars
                            #:modules (delete-duplicates
                                       `((guix build utils)
+                                        (guix build vm)
                                         ,@modules))
                            #:guile-for-build guile-for-build
                            #:references-graphs references-graphs)))

guix/build/vm.scm

@@ -0,0 +1,97 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2013, 2014 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; 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 (guix build vm)
+  #:use-module (ice-9 match)
+  #:use-module (guix build utils)
+  #:export (load-in-linux-vm))
+
+;;; Commentary:
+;;;
+;;; This module provides supporting code to run virtual machines and build
+;;; virtual machine images using QEMU.
+;;;
+;;; Code:
+
+(define (qemu-command)
+  "Return the default name of the QEMU command for the current host."
+  (string-append "qemu-system-"
+                 (substring %host-type 0
+                            (string-index %host-type #\-))))
+
+
+(define* (load-in-linux-vm builder
+                           #:key
+                           output
+                           (qemu (qemu-command)) (memory-size 512)
+                           linux initrd
+                           make-disk-image? (disk-image-size 100)
+                           (references-graphs '()))
+  "Run BUILDER, a Scheme file, into a VM running LINUX with INITRD, and copy
+the result to OUTPUT.
+
+When MAKE-DISK-IMAGE? is true, OUTPUT will contain a VM image of
+DISK-IMAGE-SIZE MiB resulting from the execution of BUILDER, which may access
+it via /dev/hda.
+
+REFERENCES-GRAPHS can specify a list of reference-graph files as produced by
+the #:references-graphs parameter of 'derivation'."
+
+  (when make-disk-image?
+    (unless (zero? (system* "qemu-img" "create" "-f" "qcow2" "image.qcow2"
+                            (number->string disk-image-size)))
+      (error "qemu-img failed")))
+
+  (mkdir "xchg")
+
+  (match references-graphs
+    ((graph-files ...)
+     ;; Copy the reference-graph files under xchg/ so EXP can access it.
+     (map (lambda (file)
+            (copy-file file (string-append "xchg/" file)))
+          graph-files))
+    (_ #f))
+
+  (unless (zero?
+           (apply system* qemu "-enable-kvm" "-nographic" "-no-reboot"
+                  "-m" (number->string memory-size)
+                  "-net" "nic,model=virtio"
+                  "-virtfs"
+                  (string-append "local,id=store_dev,path="
+                                 (%store-directory)
+                                 ",security_model=none,mount_tag=store")
+                  "-virtfs"
+                  (string-append "local,id=xchg_dev,path=xchg"
+                                 ",security_model=none,mount_tag=xchg")
+                  "-kernel" linux
+                  "-initrd" initrd
+                  "-append" (string-append "console=ttyS0 --load="
+                                           builder)
+                  (if make-disk-image?
+                      '("-hda" "image.qcow2")
+                      '())))
+    (error "qemu failed" qemu))
+
+  (if make-disk-image?
+      (copy-file "image.qcow2"            ; XXX: who mkdir'd OUTPUT?
+                 output)
+      (begin
+        (mkdir output)
+        (copy-recursively "xchg" output))))
+
+;;; vm.scm ends here