[Xen-devel] [PATCH v2] OvmfPkg: XenPvBlkDxe: handle empty cdrom drives

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Empty cdroms are not going to connect, avoid waiting for the backend to
switch to state 4, which is never going to happen, and return
error instead from XenPvBlockFrontInitialization(). Detect an
empty cdrom by looking at the "params" node on xenstore, which is set to
"" or "aio:" for empty drives by libxl.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

---
Changes in v2:
- better commit message
- return EFI_DEVICE_ERROR instead of EFI_NO_MEDIA
- check the return status of XenBusIo->XsBackendRead
---
 OvmfPkg/XenPvBlkDxe/BlockFront.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/OvmfPkg/XenPvBlkDxe/BlockFront.c b/OvmfPkg/XenPvBlkDxe/BlockFront.c
index 256ac55..d07e980 100644
--- a/OvmfPkg/XenPvBlkDxe/BlockFront.c
+++ b/OvmfPkg/XenPvBlkDxe/BlockFront.c
@@ -169,6 +169,7 @@ XenPvBlockFrontInitialization (
   XEN_BLOCK_FRONT_DEVICE *Dev;
   XenbusState State;
   UINT64 Value;
+  CHAR8 *Params;
 
   ASSERT (NodeName != NULL);
 
@@ -186,6 +187,20 @@ XenPvBlockFrontInitialization (
   }
   FreePool (DeviceType);
 
+  if (Dev->MediaInfo.CdRom) {
+    Status = XenBusIo->XsBackendRead (XenBusIo, XST_NIL, "params", 
(VOID**)&Params);
+    if (Status != XENSTORE_STATUS_SUCCESS) {
+      DEBUG ((EFI_D_ERROR, "%a: Failed to read params (%d)\n", __FUNCTION__, 
Status));
+      goto Error;
+    }
+    if (AsciiStrLen (Params) == 0 || AsciiStrCmp (Params, "aio:") == 0) {
+      FreePool (Params);
+      DEBUG ((EFI_D_INFO, "%a: Empty cdrom\n", __FUNCTION__));
+      goto Error;
+    }
+    FreePool (Params);
+  }
+
   Status = XenBusReadUint64 (XenBusIo, "backend-id", FALSE, &Value);
   if (Status != XENSTORE_STATUS_SUCCESS || Value > MAX_UINT16) {
     DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to get backend-id (%d)\n",
-- 
1.7.10.4


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