Re: [XENBUS PATCH] emulated: Detect emulated NVMe controllers

[Owen Smith <owen.smith@xxxxxxxxx>]

Reviewed-by: Owen Smith <owen.smith@xxxxxxxxx>

On Tue, Sep 9, 2025 at 9:37 AM Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx> wrote:

Xenfilt currently can't distinguish between a real NVMe controller and
one emulated by QEMU. This will cause EmulatedIsDiskPresent to always
report as true, causing Xenvbd to skip target creation if a real NVMe
controller is passed through to the guest.

Stop saving just a single CompatibleID in XENFILT_EMULATED_DEVICE_DATA.
Instead, add logic to EmulatedSetObjectDeviceData to explicitly detect
emulated NVMe controllers using their PCI vendor/device IDs.

Reported-by: Keshab Upadhya <keshab@xxxxxxxxxx>
Link: https://github.com/xcp-ng/win-pv-drivers/issues/21
Signed-off-by: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>
---
 src/xenfilt/emulated.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/src/xenfilt/emulated.c b/src/xenfilt/emulated.c
index 4205cc5..cbe90b0 100644
--- a/src/xenfilt/emulated.c
+++ b/src/xenfilt/emulated.c
@@ -47,8 +47,8 @@
 typedef struct _XENFILT_EMULATED_DEVICE_DATA {
     CHAR                                DeviceID[MAXNAMELEN];
     CHAR                                InstanceID[MAXNAMELEN];
-    CHAR                                CompatibleID[MAXNAMELEN];
     XENBUS_EMULATED_ACTIVATION_STATUS   ForceActivate;
+    BOOLEAN                             IsEmulatedNvme;
 } XENFILT_EMULATED_DEVICE_DATA, *PXENFILT_EMULATED_DEVICE_DATA;

 typedef struct _XENFILT_EMULATED_DISK_DATA {
@@ -100,7 +100,6 @@ EmulatedSetObjectDeviceData(
     )
 {
     ULONG                               Index;
-    PSTR                                LastMatch;
     NTSTATUS                            status;

     status = STATUS_INVALID_PARAMETER;
@@ -123,7 +122,6 @@ EmulatedSetObjectDeviceData(
         goto done;

     Index = 0;
-    LastMatch = CompatibleIDs;
     for (;;) {
         ULONG   Length;

@@ -131,17 +129,17 @@ EmulatedSetObjectDeviceData(
         if (Length == 0)
             break;

-        LastMatch = &CompatibleIDs[Index];
+        // 8086:5845 and 1B36:0010 are the IDs of the QEMU NVMe controller when
+        // "use-intel-id" is on and off respectively.
+        if (_stricmp(&CompatibleIDs[Index], "PCI\\VEN_8086&DEV_5845") == 0 ||
+            _stricmp(&CompatibleIDs[Index], "PCI\\VEN_1B36&DEV_0010") == 0) {
+            EmulatedObject->Data.Device.IsEmulatedNvme = TRUE;
+            break;
+        }

         Index += Length + 1;
     }

-    status = RtlStringCbPrintfA(EmulatedObject->Data.Device.CompatibleID,
-                                MAXNAMELEN,
-                                "%s",
-                                LastMatch);
-    ASSERT(NT_SUCCESS(status));
-
 done:
     return STATUS_SUCCESS;

@@ -418,8 +416,7 @@ EmulatedIsDiskPresent(
         }

         if (EmulatedObject->Type == XENFILT_EMULATED_OBJECT_TYPE_PCI &&
-            _stricmp("PCI\\CC_0108", EmulatedObject->Data.Device.CompatibleID) == 0 &&
-            Index <= 3) {
+            EmulatedObject->Data.Device.IsEmulatedNvme) {
             Trace("FOUND\n");
             break;
         }
--
2.51.0.windows.1



--
Ngoc Tu Dinh | Vates XCP-ng Developer

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