Re: [PATCH] Add UseConsole parameter to disable default console

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

On 26/10/2026 11:15, Owen Smith wrote:
> By setting "UseConsole" = 1, the default console (and CONSOLE) interface will 
> fail.
> The default console's PDO will still be created, but any attempt to call 
> CreateFile will
> fail, so I'd assume any alternate use would need to manage the default 
> console ring
> itself. Non-default console's PDOs are unaffected.
> 

My idea is to totally prevent xenbus and others from touching the 
default console ring and leave the console ring's usage to some other 
applications. That seemed simpler than swallowing read/write requests at 
first glance.

 From my testing, it looks like I can still open handles to the default 
console PDO XENCONS\VEN_XN&DEV_CONSOLE\0 (e.g. Get-NtFile -Access 
ReadData,WriteData,Synchronize -ShareMode Delete \Device\...). Although 
I haven't tested this point further.

> Owen
> 
> 
> ________________________________________
> From: win-pv-devel <win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx> on behalf of 
> Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>
> Sent: 26 October 2026 6:57 AM
> To: win-pv-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Tu Dinh
> Subject: [PATCH] Add UseConsole parameter to disable default console
> 
> In some cases, we may want to assign the default console to something
> else (e.g. a debug transport). So add a parameter to allow disabling it.
> 
> Signed-off-by: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>
> ---
>   src/xenbus/console.c | 68 ++++++++++++++++++++++++++++++--------------
>   1 file changed, 47 insertions(+), 21 deletions(-)
> 
> diff --git a/src/xenbus/console.c b/src/xenbus/console.c
> index 2d747cb..0bfe504 100644
> --- a/src/xenbus/console.c
> +++ b/src/xenbus/console.c
> @@ -43,6 +43,8 @@
>   #include "dbg_print.h"
>   #include "assert.h"
>   #include "util.h"
> +#include "driver.h"
> +#include "registry.h"
> 
>   #define CONSOLE_WAKEUP_MAGIC 'EKAW'
> 
> @@ -71,6 +73,7 @@ struct _XENBUS_CONSOLE_CONTEXT {
>       XENBUS_DEBUG_INTERFACE      DebugInterface;
>       PXENBUS_SUSPEND_CALLBACK    SuspendCallbackLate;
>       PXENBUS_DEBUG_CALLBACK      DebugCallback;
> +    BOOLEAN                     UseConsole;
>       BOOLEAN                     Enabled;
>   };
> 
> @@ -692,13 +695,17 @@ ConsoleAcquire(
> 
>       Trace("====>\n");
> 
> +    status = STATUS_NOT_SUPPORTED;
> +    if (!Context->UseConsole)
> +        goto fail1;
> +
>       status = XENBUS_GNTTAB(Acquire, &Context->GnttabInterface);
>       if (!NT_SUCCESS(status))
> -        goto fail1;
> +        goto fail2;
> 
>       status = ConsoleGetAddress(Context, &Address);
>       if (!NT_SUCCESS(status))
> -        goto fail2;
> +        goto fail3;
> 
>       Context->Address = Address;
>       Context->Shared = (struct xencons_interface 
> *)MmMapIoSpace(Context->Address,
> @@ -706,19 +713,19 @@ ConsoleAcquire(
>                                                                  MmCached);
>       status = STATUS_UNSUCCESSFUL;
>       if (Context->Shared == NULL)
> -        goto fail3;
> +        goto fail4;
> 
>       status = XENBUS_EVTCHN(Acquire, &Context->EvtchnInterface);
>       if (!NT_SUCCESS(status))
> -        goto fail4;
> +        goto fail5;
> 
>       status = ConsoleEnable(Context);
>       if (!NT_SUCCESS(status))
> -        goto fail5;
> +        goto fail6;
> 
>       status = XENBUS_SUSPEND(Acquire, &Context->SuspendInterface);
>       if (!NT_SUCCESS(status))
> -        goto fail6;
> +        goto fail7;
> 
>       status = XENBUS_SUSPEND(Register,
>                               &Context->SuspendInterface,
> @@ -727,11 +734,11 @@ ConsoleAcquire(
>                               Context,
>                               &Context->SuspendCallbackLate);
>       if (!NT_SUCCESS(status))
> -        goto fail7;
> +        goto fail8;
> 
>       status = XENBUS_DEBUG(Acquire, &Context->DebugInterface);
>       if (!NT_SUCCESS(status))
> -        goto fail8;
> +        goto fail9;
> 
>       status = XENBUS_DEBUG(Register,
>                             &Context->DebugInterface,
> @@ -740,7 +747,7 @@ ConsoleAcquire(
>                             Context,
>                             &Context->DebugCallback);
>       if (!NT_SUCCESS(status))
> -        goto fail9;
> +        goto fail10;
> 
>       Trace("<====\n");
> 
> @@ -749,50 +756,53 @@ done:
> 
>       return STATUS_SUCCESS;
> 
> -fail9:
> -    Error("fail9\n");
> +fail10:
> +    Error("fail10\n");
> 
>       XENBUS_DEBUG(Release, &Context->DebugInterface);
> 
> -fail8:
> -    Error("fail8\n");
> +fail9:
> +    Error("fail9\n");
> 
>       XENBUS_SUSPEND(Deregister,
>                      &Context->SuspendInterface,
>                      Context->SuspendCallbackLate);
>       Context->SuspendCallbackLate = NULL;
> 
> +fail8:
> +    Error("fail8\n");
> +
> +    XENBUS_SUSPEND(Release, &Context->SuspendInterface);
> +
>   fail7:
>       Error("fail7\n");
> 
> -    XENBUS_SUSPEND(Release, &Context->SuspendInterface);
> +    ConsoleDisable(Context);
> 
>   fail6:
>       Error("fail6\n");
> 
> -    ConsoleDisable(Context);
> +    XENBUS_EVTCHN(Release, &Context->EvtchnInterface);
> 
>   fail5:
>       Error("fail5\n");
> 
> -    XENBUS_EVTCHN(Release, &Context->EvtchnInterface);
> +    MmUnmapIoSpace(Context->Shared, PAGE_SIZE);
> +    Context->Shared = NULL;
> 
>   fail4:
>       Error("fail4\n");
> 
> -    MmUnmapIoSpace(Context->Shared, PAGE_SIZE);
> -    Context->Shared = NULL;
> +    Context->Address.QuadPart = 0;
> 
>   fail3:
>       Error("fail3\n");
> 
> -    Context->Address.QuadPart = 0;
> +    XENBUS_GNTTAB(Release, &Context->GnttabInterface);
> 
>   fail2:
>       Error("fail2\n");
> 
> -    XENBUS_GNTTAB(Release, &Context->GnttabInterface);
> -
>   fail1:
>       Error("fail1 (%08x)\n", status);
> 
> @@ -872,6 +882,8 @@ ConsoleInitialize(
>       _Outptr_ PXENBUS_CONSOLE_CONTEXT    *Context
>       )
>   {
> +    HANDLE                              ParametersKey;
> +    ULONG                               UseConsole;
>       NTSTATUS                            status;
> 
>       Trace("====>\n");
> @@ -917,6 +929,19 @@ ConsoleInitialize(
> 
>       KeInitializeDpc(&(*Context)->Dpc, ConsoleDpc, *Context);
> 
> +    ParametersKey = DriverGetParametersKey();
> +
> +    status = RegistryQueryDwordValue(ParametersKey,
> +                                     "UseConsole",
> +                                     &UseConsole);
> +    if (!NT_SUCCESS(status))
> +        UseConsole = 1;
> +
> +    (*Context)->UseConsole = (UseConsole != 0) ? TRUE : FALSE;
> +
> +    if (!(*Context)->UseConsole)
> +        Info("DISABLED\n");
> +
>       (*Context)->Fdo = Fdo;
> 
>       Trace("<====\n");
> @@ -988,6 +1013,7 @@ ConsoleTeardown(
>       Context->Dpcs = 0;
>       Context->Events = 0;
> 
> +    Context->UseConsole = FALSE;
>       Context->Fdo = NULL;
> 
>       RtlZeroMemory(&Context->Dpc, sizeof (KDPC));
> --
> 2.56.0.windows.3
> 
> 
> 
> --
> Ngoc Tu Dinh | Vates XCP-ng Developer
> 
> XCP-ng & Xen Orchestra - Vates solutions
> 
> web: https://vates.tech
> 



--
Ngoc Tu Dinh | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech