1 files changed, 27 insertions, 3 deletions
diff --git a/gnu/build/vm.scm b/gnu/build/vm.scm
index 6d6a0c4cb4..ac99d6b1a3 100644
--- a/gnu/build/vm.scm
+++ b/gnu/build/vm.scm
@@ -37,6 +37,7 @@
   #:use-module (ice-9 popen)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-19)
   #:use-module (srfi srfi-26)
   #:export (qemu-command
             load-in-linux-vm
@@ -144,6 +145,7 @@ the #:references-graphs parameter of 'derivation'."
     (_ #f))
 
   (apply invoke qemu "-nographic" "-no-reboot"
+         "-smp" (number->string (parallel-job-count))
          "-m" (number->string memory-size)
          "-object" "rng-random,filename=/dev/urandom,id=guixsd-vm-rng"
          "-device" "virtio-rng-pci,rng=guixsd-vm-rng"
@@ -458,6 +460,29 @@ GRUB configuration and OS-DRV as the stuff in it."
               closures)
     (register-bootcfg-root "/tmp/root" config-file))
 
+  ;; 'grub-mkrescue' calls out to mtools programs to create 'efi.img', a FAT
+  ;; file system image, and mtools honors SOURCE_DATE_EPOCH for the mtime of
+  ;; those files.  The epoch for FAT is Jan. 1st 1980, not 1970, so choose
+  ;; that.
+  (setenv "SOURCE_DATE_EPOCH"
+          (number->string
+           (time-second
+            (date->time-utc (make-date 0 0 0 0 1 1 1980 0)))))
+
+  ;; Our patched 'grub-mkrescue' honors this environment variable and passes
+  ;; it to 'mformat', which makes it the serial number of 'efi.img'.  This
+  ;; allows for deterministic builds.
+  (setenv "GRUB_FAT_SERIAL_NUMBER"
+          (number->string (if volume-uuid
+
+                              ;; On 32-bit systems the 2nd argument must be
+                              ;; lower than 2^32.
+                              (string-hash (iso9660-uuid->string volume-uuid)
+                                           (- (expt 2 32) 1))
+
+                              #x77777777)
+                          16))
+
   (let ((pipe
          (apply open-pipe* OPEN_WRITE
                 grub-mkrescue "-o" target
@@ -472,9 +497,8 @@ GRUB configuration and OS-DRV as the stuff in it."
                 "-path-list" "-"
                 "--"
 
-                ;; XXX: Add padding to avoid I/O errors on i686:
-                ;; <https://bugs.gnu.org/33639>.
-                "-padding" "10m"
+                ;; Set all timestamps to 1.
+                "-volume_date" "all_file_dates" "=1"
 
                 "-volid" (string-upcase volume-id)
                 (if volume-uuid