Re: [PATCH 3/5] Remove StartOverride from all PCI storage adapters

["Tu Dinh" <ngoc-tu.dinh@xxxxxxxxxx>]

On 06/02/2026 09:45, Owen Smith wrote:
> Its possible to install non-Microsoft NVMe drivers on the emulated
> NVMe device. During upgrades, the VM requires a reboot using the emulated
> devices, but if the driver assigned for the emulated device has a 
> StartOverride
> setting, then its likely not started which results in a 0x7B bugcheck.
> 
> Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>


Enum key is explicitly reserved by Microsoft and should not be accessed 
directly:
https://learn.microsoft.com/en-us/windows-hardware/drivers/install/hklm-system-currentcontrolset-enum-registry-tree

I think SetupAPI/CM API should be used instead.

> ---
>   src/monitor/monitor.c | 191 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 191 insertions(+)
> 
> diff --git a/src/monitor/monitor.c b/src/monitor/monitor.c
> index 52311aa..61945f0 100644
> --- a/src/monitor/monitor.c
> +++ b/src/monitor/monitor.c
> @@ -90,6 +90,12 @@ MONITOR_CONTEXT MonitorContext;
>   #define PARAMETERS_KEY(_Service) \
>           SERVICE_KEY(_Service) ## "\\Parameters"
>   
> +#define ENUM_KEY(_Class) \
> +        "SYSTEM\\CurrentControlSet\\Enum\\" ## _Class
> +
> +#define STORAGE_CLASS_GUID \
> +        "{4d36e97b-e325-11ce-bfc1-08002be10318}"
> +

Perhaps GUID_DEVCLASS_HDC should be checked as well.

>   static VOID
>   #pragma prefast(suppress:6262) // Function uses '1036' bytes of stack: 
> exceeds /analyze:stacksize'1024'
>   __Log(
> @@ -1393,6 +1399,189 @@ fail1:
>       return FALSE;
>   }
>   
> +static BOOLEAN
> +RemoveStartOverrideInstance(
> +    _In_ HKEY           BaseKey,
> +    _In_ PTSTR          SubKeyName,
> +    _In_opt_ PVOID      Context
> +    )
> +{
> +    DWORD               Type;
> +    PTSTR               Value;
> +    DWORD               ValueLength;
> +    DWORD               MaxValueLength;
> +    HKEY                SubKey;
> +    HRESULT             Error;
> +
> +    UNREFERENCED_PARAMETER(Context);
> +
> +    Error = RegOpenKeyEx(BaseKey,
> +                         SubKeyName,
> +                         0,
> +                         KEY_READ,
> +                         &SubKey);
> +    if (Error != ERROR_SUCCESS)
> +        return TRUE;
> +
> +    Error = RegQueryInfoKey(SubKey,
> +                            NULL,
> +                            NULL,
> +                            NULL,
> +                            NULL,
> +                            NULL,
> +                            NULL,
> +                            NULL,
> +                            NULL,
> +                            &MaxValueLength,
> +                            NULL,
> +                            NULL);
> +    if (Error != ERROR_SUCCESS) {
> +        SetLastError(Error);
> +        goto fail1;
> +    }
> +
> +    ValueLength = MaxValueLength + sizeof (TCHAR);
> +
> +    Value = calloc(1, ValueLength);
> +    if (Value == NULL)
> +        goto fail2;
> +
> +    Error = RegQueryValueEx(SubKey,
> +                            "ClassGUID",
> +                            NULL,
> +                            &Type,
> +                            (LPBYTE)Value,
> +                            &ValueLength);
> +    if (Error != ERROR_SUCCESS) {
> +        SetLastError(Error);
> +        goto fail3;
> +    }
> +
> +    if (Type != REG_SZ) {
> +        SetLastError(ERROR_BAD_FORMAT);
> +        goto fail4;
> +    }
> +
> +    if (_tcsnicmp(Value, STORAGE_CLASS_GUID, ValueLength) != 0)
> +        goto done;
> +
> +    ValueLength = MaxValueLength + sizeof (TCHAR);
> +    memset(Value, 0, ValueLength);
> +
> +    Error = RegQueryValueEx(SubKey,
> +                            "Service",
> +                            NULL,
> +                            &Type,
> +                            (LPBYTE)Value,
> +                            &ValueLength);
> +    if (Error != ERROR_SUCCESS) {
> +        SetLastError(Error);
> +        goto fail5;
> +    }
> +
> +    if (Type != REG_SZ) {
> +        SetLastError(ERROR_BAD_FORMAT);
> +        goto fail6;
> +    }
> +
> +    RemoveStartOverride(Value);
> +
> +done:
> +    free(Value);
> +
> +    RegCloseKey(SubKey);
> +
> +    return TRUE;
> +
> +fail6:
> +    Log("fail6");
> +
> +fail5:
> +    Log("fail5");
> +
> +fail4:
> +    Log("fail4");
> +
> +fail3:
> +    Log("fail3");
> +
> +    free(Value);
> +
> +fail2:
> +    Log("fail2");
> +
> +fail1:
> +    Log("fail1");
> +
> +    return TRUE;
> +}
> +
> +static BOOLEAN
> +RemoveStartOverrideDevice(
> +    _In_ HKEY           BaseKey,
> +    _In_ PTSTR          SubKeyName,
> +    _In_opt_ PVOID      Context
> +    )
> +{
> +    HKEY                SubKey;
> +    HRESULT             Error;
> +
> +    UNREFERENCED_PARAMETER(Context);
> +
> +    Error = RegOpenKeyEx(BaseKey,
> +                         SubKeyName,
> +                         0,
> +                         KEY_READ,
> +                         &SubKey);
> +    if (Error != ERROR_SUCCESS)
> +        return TRUE;
> +
> +    (VOID) RegEnumSubKeys(SubKey,
> +                          RemoveStartOverrideInstance,
> +                          NULL);
> +
> +    RegCloseKey(SubKey);
> +
> +    return TRUE;
> +}
> +
> +static BOOL
> +RemoveAllStartOverrides(
> +    VOID
> +    )
> +{
> +    HKEY            EnumKey;
> +    HRESULT         Error;
> +
> +    Error = RegOpenKeyEx(HKEY_LOCAL_MACHINE,
> +                         ENUM_KEY("PCI"),
> +                         0,
> +                         KEY_READ,
> +                         &EnumKey);
> +    if (Error != ERROR_SUCCESS) {
> +        goto fail1;
> +    }
> +
> +    Error = RegEnumSubKeys(EnumKey,
> +                           RemoveStartOverrideDevice,
> +                           NULL);
> +    if (Error != ERROR_SUCCESS) {
> +        goto fail2;
> +    }
> +
> +    RegCloseKey(EnumKey);
> +
> +    return TRUE;
> +
> +fail2:
> +    Log("fail2");
> +
> +fail1:
> +    Log("fail1");
> +
> +    return FALSE;
> +}
> +
>   VOID WINAPI
>   MonitorMain(
>       _In_    DWORD       argc,
> @@ -1411,6 +1600,7 @@ MonitorMain(
>       Log("====>");
>   
>       (VOID) RemoveStartOverride("stornvme");
> +    (VOID) RemoveAllStartOverrides();
>   
>       Error = RegOpenKeyEx(HKEY_LOCAL_MACHINE,
>                            PARAMETERS_KEY(__MODULE__),
> @@ -1565,6 +1755,7 @@ done:
>   
>       CloseHandle(Context->ParametersKey);
>       (VOID) RemoveStartOverride("stornvme");
> +    (VOID) RemoveAllStartOverrides();
>   
>       Log("<====");
>   



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