[PATCH 15/26] qemu: add config parameter to control auto-save bypass cache

[Daniel P. Berrangé <berrange@xxxxxxxxxx>]

When doing managed save of VMs, triggered by OS shutdown, it may
be desirable to control cache usage.

Signed-off-by: Daniel P. Berrangé <berrange@xxxxxxxxxx>
---
 src/qemu/libvirtd_qemu.aug         | 1 +
 src/qemu/qemu.conf.in              | 8 ++++++++
 src/qemu/qemu_conf.c               | 3 +++
 src/qemu/qemu_conf.h               | 1 +
 src/qemu/qemu_driver.c             | 1 +
 src/qemu/test_libvirtd_qemu.aug.in | 1 +
 6 files changed, 15 insertions(+)

diff --git a/src/qemu/libvirtd_qemu.aug b/src/qemu/libvirtd_qemu.aug
index 8cb1b144b9..9fa6398d8d 100644
--- a/src/qemu/libvirtd_qemu.aug
+++ b/src/qemu/libvirtd_qemu.aug
@@ -102,6 +102,7 @@ module Libvirtd_qemu =
                  | str_entry "auto_shutdown_try_shutdown"
                  | str_entry "auto_shutdown_poweroff"
                  | int_entry "auto_shutdown_wait"
+                 | bool_entry "auto_save_bypass_cache"
 
    let process_entry = str_entry "hugetlbfs_mount"
                  | str_entry "bridge_helper"
diff --git a/src/qemu/qemu.conf.in b/src/qemu/qemu.conf.in
index 9287196c42..d26ab4cb57 100644
--- a/src/qemu/qemu.conf.in
+++ b/src/qemu/qemu.conf.in
@@ -681,6 +681,14 @@
 # when 'auto_shutdown_try_shutdown' is enabled
 #auto_shutdown_wait = 30
 
+# When a domain is configured to be auto-saved on shutdown, enabling
+# this flag has the same effect as using the VIR_DOMAIN_SAVE_BYPASS_CACHE
+# flag with the virDomainManagedSave API.  That is, the system will
+# avoid using the file system cache when writing any managed state
+# file, but may cause slower operation.
+#
+#auto_save_bypass_cache = 0
+
 # If provided by the host and a hugetlbfs mount point is configured,
 # a guest may request huge page backing.  When this mount point is
 # unspecified here, determination of a host mount point in /proc/mounts
diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index 7ec682e533..af09920869 100644
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -695,6 +695,9 @@ virQEMUDriverConfigLoadSaveEntry(virQEMUDriverConfig *cfg,
     if (virConfGetValueInt(conf, "auto_shutdown_wait",
                            &cfg->autoShutdownWait) < 0)
         return -1;
+    if (virConfGetValueBool(conf, "auto_save_bypass_cache",
+                            &cfg->autoSaveBypassCache) < 0)
+        return -1;
 
     return 0;
 }
diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
index b8f6be110d..9818a8cbb5 100644
--- a/src/qemu/qemu_conf.h
+++ b/src/qemu/qemu_conf.h
@@ -205,6 +205,7 @@ struct _virQEMUDriverConfig {
     int autoShutdownTryShutdown;
     int autoShutdownPoweroff;
     int autoShutdownWait;
+    bool autoSaveBypassCache;
 
     char *lockManagerName;
 
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index baa0d51244..8729b0fab0 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -951,6 +951,7 @@ qemuStateStop(void)
         .tryShutdown = cfg->autoShutdownTryShutdown,
         .poweroff = cfg->autoShutdownPoweroff,
         .waitShutdownSecs = cfg->autoShutdownWait,
+        .saveBypassCache = cfg->autoSaveBypassCache,
     };
 
     virDomainDriverAutoShutdown(&ascfg);
diff --git a/src/qemu/test_libvirtd_qemu.aug.in b/src/qemu/test_libvirtd_qemu.aug.in
index 4c6de31199..65d0c20fe1 100644
--- a/src/qemu/test_libvirtd_qemu.aug.in
+++ b/src/qemu/test_libvirtd_qemu.aug.in
@@ -80,6 +80,7 @@ module Test_libvirtd_qemu =
 { "auto_shutdown_try_shutdown" = "all" }
 { "auto_shutdown_poweroff" = "all" }
 { "auto_shutdown_wait" = "30" }
+{ "auto_save_bypass_cache" = "0" }
 { "hugetlbfs_mount" = "/dev/hugepages" }
 { "bridge_helper" = "qemu-bridge-helper" }
 { "set_process_name" = "1" }
-- 
2.47.1