[PATCH 07/13] tests/avocado/kvm_xen_guest.py: cope with asset RW requirements

[Cleber Rosa <crosa@redhat.com>]

Some of these tests actually require the root filesystem image,
obtained through Avocado's asset feature and kept in a common cache
location, to be writable.

This makes a distinction between the tests that actually have this
requirement and those who don't.  The goal is to be as safe as
possible, avoiding causing cache misses (because the assets get
modified and thus need to be dowloaded again) while avoid copying the
root filesystem backing file whenever possible.

This also allow these tests to be run in parallel with newer Avocado
versions.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
---
 tests/avocado/kvm_xen_guest.py | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/tests/avocado/kvm_xen_guest.py b/tests/avocado/kvm_xen_guest.py
index 318fadebc3..d73fa888ef 100644
--- a/tests/avocado/kvm_xen_guest.py
+++ b/tests/avocado/kvm_xen_guest.py
@@ -10,6 +10,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 import os
+import shutil
 
 from qemu.machine import machine
 
@@ -43,7 +44,7 @@ def get_asset(self, name, sha1):
         return self.fetch_asset(name=f"qemu-kvm-xen-guest-{name}",
                                 locations=(url), asset_hash=sha1)
 
-    def common_vm_setup(self):
+    def common_vm_setup(self, readwrite=False):
         # We also catch lack of KVM_XEN support if we fail to launch
         self.require_accelerator("kvm")
 
@@ -56,11 +57,19 @@ def common_vm_setup(self):
                                           "367962983d0d32109998a70b45dcee4672d0b045")
         self.rootfs = self.get_asset("rootfs.ext4",
                                      "f1478401ea4b3fa2ea196396be44315bab2bb5e4")
+        if readwrite:
+            dest = os.path.join(self.workdir, os.path.basename(self.rootfs))
+            shutil.copy(self.rootfs, dest)
+            self.rootfs = dest
 
-    def run_and_check(self):
+    def run_and_check(self, readwrite=False):
+        if readwrite:
+            drive = f"file={self.rootfs},if=none,format=raw,id=drv0"
+        else:
+            drive = f"file={self.rootfs},if=none,readonly=on,format=raw,id=drv0"
         self.vm.add_args('-kernel', self.kernel_path,
                          '-append', self.kernel_params,
-                         '-drive',  f"file={self.rootfs},if=none,snapshot=on,format=raw,id=drv0",
+                         '-drive',  drive,
                          '-device', 'xen-disk,drive=drv0,vdev=xvda',
                          '-device', 'virtio-net-pci,netdev=unet',
                          '-netdev', 'user,id=unet,hostfwd=:127.0.0.1:0-:22')
@@ -90,11 +99,11 @@ def test_kvm_xen_guest(self):
         :avocado: tags=kvm_xen_guest
         """
 
-        self.common_vm_setup()
+        self.common_vm_setup(True)
 
         self.kernel_params = (self.KERNEL_DEFAULT +
                               ' xen_emul_unplug=ide-disks')
-        self.run_and_check()
+        self.run_and_check(True)
         self.ssh_command('grep xen-pirq.*msi /proc/interrupts')
 
     def test_kvm_xen_guest_nomsi(self):
@@ -102,11 +111,11 @@ def test_kvm_xen_guest_nomsi(self):
         :avocado: tags=kvm_xen_guest_nomsi
         """
 
-        self.common_vm_setup()
+        self.common_vm_setup(True)
 
         self.kernel_params = (self.KERNEL_DEFAULT +
                               ' xen_emul_unplug=ide-disks pci=nomsi')
-        self.run_and_check()
+        self.run_and_check(True)
         self.ssh_command('grep xen-pirq.* /proc/interrupts')
 
     def test_kvm_xen_guest_noapic_nomsi(self):
@@ -114,11 +123,11 @@ def test_kvm_xen_guest_noapic_nomsi(self):
         :avocado: tags=kvm_xen_guest_noapic_nomsi
         """
 
-        self.common_vm_setup()
+        self.common_vm_setup(True)
 
         self.kernel_params = (self.KERNEL_DEFAULT +
                               ' xen_emul_unplug=ide-disks noapic pci=nomsi')
-        self.run_and_check()
+        self.run_and_check(True)
         self.ssh_command('grep xen-pirq /proc/interrupts')
 
     def test_kvm_xen_guest_vapic(self):
-- 
2.45.2