[PATCH v2 4/4] qemu: add support for 'multidevs' option

[Christian Schoenebeck <qemu_oss@xxxxxxxxxxxxx>]

This option prevents misbehaviours on guest if a qemu 9pfs export
contains multiple devices, due to the potential file ID collisions
this otherwise may cause.

Signed-off-by: Christian Schoenebeck <qemu_oss@xxxxxxxxxxxxx>
---
 src/qemu/qemu_command.c |  7 +++++++
 src/qemu/qemu_domain.c  | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 9790c92cf8..7020e5448c 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -2632,6 +2632,13 @@ qemuBuildFSStr(virDomainFSDefPtr fs)
         } else if (fs->accessmode == VIR_DOMAIN_FS_ACCESSMODE_SQUASH) {
             virBufferAddLit(&opt, ",security_model=none");
         }
+        if (fs->multidevs == VIR_DOMAIN_FS_MULTIDEVS_REMAP) {
+            virBufferAddLit(&opt, ",multidevs=remap");
+        } else if (fs->multidevs == VIR_DOMAIN_FS_MULTIDEVS_FORBID) {
+            virBufferAddLit(&opt, ",multidevs=forbid");
+        } else if (fs->multidevs == VIR_DOMAIN_FS_MULTIDEVS_WARN) {
+            virBufferAddLit(&opt, ",multidevs=warn");
+        }
     } else if (fs->fsdriver == VIR_DOMAIN_FS_DRIVER_TYPE_HANDLE) {
         /* removed since qemu 4.0.0 see v3.1.0-29-g93aee84f57 */
         virBufferAddLit(&opt, "handle");
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index edc8ba2ddb..c54c64fadb 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -8529,6 +8529,13 @@ qemuDomainDeviceDefValidateFS(virDomainFSDefPtr fs,
                        _("only supports mount filesystem type"));
         return -1;
     }
+    if (fs->multidevs != VIR_DOMAIN_FS_MODEL_DEFAULT &&
+        !virQEMUCapsGet(qemuCaps, QEMU_CAPS_VIRTFS_MULTIDEVS))
+    {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("multidevs is not supported with this QEMU binary"));
+        return -1;
+    }
 
     switch ((virDomainFSDriverType) fs->fsdriver) {
     case VIR_DOMAIN_FS_DRIVER_TYPE_DEFAULT:
@@ -8581,6 +8588,11 @@ qemuDomainDeviceDefValidateFS(virDomainFSDefPtr fs,
                            _("virtiofs is not supported with this QEMU binary"));
             return -1;
         }
+        if (fs->multidevs != VIR_DOMAIN_FS_MULTIDEVS_DEFAULT) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("virtiofs does not support multidevs"));
+            return -1;
+        }
         if (qemuDomainDefValidateVirtioFSSharedMemory(def) < 0)
             return -1;
         break;
-- 
2.20.1