RE: Patch "Documentation: hyperv: Update documentation for sending VMBus packets" has been added to the 6.12-stable tree

RE: Patch "Documentation: hyperv: Update documentation for sending VMBus packets" has been added to the 6.12-stable tree

[Michael Kelley]

From: Sasha Levin <sashal@kernel.org> Sent: Friday, November 6, 2026 6:29 PM
> To: stable-commits@vger.kernel.org; mhkelley58@gmail.com
> Cc: Haiyang Zhang <haiyangz@microsoft.com>; Wei Liu <wei.liu@kernel.org>; Dexuan
> Cui <decui@microsoft.com>; Jonathan Corbet <corbet@lwn.net>; Shuah Khan
> <skhan@linuxfoundation.org>; Randy Dunlap <rdunlap@infradead.org>
> Subject: Patch "Documentation: hyperv: Update documentation for sending VMBus
> packets" has been added to the 6.12-stable tree
>
> This is a note to let you know that I've just added the patch titled
>
>     Documentation: hyperv: Update documentation for sending VMBus packets
>
> to the 6.12-stable tree which can be found at:
>
> http://www.kernel.org/
> %2Fgit%2F%3Fp%3Dlinux%2Fkernel%2Fgit%2Fstable%2Fstable-
> queue.git%3Ba%3Dsummary&data=05%7C02%7C%7C63b6148b45d244e7595b08df
> 3c76d448%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C63929615319498
> 0658%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMD
> AwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sd
> ata=JAjkSZKxRGOy7x1gtCMHiJQ7gPQl6NwynwtEJTqr1Oo%3D&reserved=0
>
> The filename of the patch is:
>      documentation-hyperv-update-documentation-for-sendin.patch
> and it can be found in the queue-6.12 subdirectory.
>
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@vger.kernel.org> know about it.

This patch should not be backported to earlier than 6.15, as
vmbus_sendpacket_pagebuffer() was removed in 6.15.

Michael

>
>
>
> commit 0f601aa7a87ab29b179f735be1e31b6833222a7e
> Author: Michael Kelley <mhkelley58@gmail.com>
> Date:   Mon Oct 12 18:43:54 2026 -0700
>
>     Documentation: hyperv: Update documentation for sending VMBus packets
>
>     [ Upstream commit 6a3d77a0a8cf69cf3d234305e6711729eb5d10c4 ]
>
>     The functions for sending VMBus packets have changed.
>     vmbus_sendpacket_mpb_desc() can target multiple ranges, and
>     vmbus_sendpacket_pagebuffer() has been removed. vmbus_sendpacket_getid()
>     has been added. Update the documentation accordingly.
>
>     Fixes: 45a442fe369e ("Drivers: hv: vmbus: Remove
> vmbus_sendpacket_pagebuffer()")
>     Cc: stable@vger.kernel.org
>     Signed-off-by: Michael Kelley <mhklinux@outlook.com>
>     Reviewed-by: Naman Jain <namjain@linux.microsoft.com>
>     Signed-off-by: Wei Liu <wei.liu@kernel.org>
>     Signed-off-by: Sasha Levin <sashal@kernel.org>
>
> diff --git a/Documentation/virt/hyperv/vmbus.rst
> b/Documentation/virt/hyperv/vmbus.rst
> index 1dcef6a7fda3f..7ee27faf5e5bd 100644
> --- a/Documentation/virt/hyperv/vmbus.rst
> +++ b/Documentation/virt/hyperv/vmbus.rst
> @@ -141,14 +141,15 @@ Three functions exist to send VMBus channel messages:
>
>  1. vmbus_sendpacket():  Control-only messages and messages with
>     embedded data -- no GPAs
> -2. vmbus_sendpacket_pagebuffer(): Message with list of GPAs
> -   identifying data to transfer.  An offset and length is
> -   associated with each GPA so that multiple discontinuous areas
> -   of guest memory can be targeted.
> -3. vmbus_sendpacket_mpb_desc(): Message with list of GPAs
> -   identifying data to transfer.  A single offset and length is
> -   associated with a list of GPAs.  The GPAs must describe a
> -   single logical area of guest memory to be targeted.
> +2. vmbus_sendpacket_getid(): Similar to vmbus_sendpacket() but returns
> +   a transaction ID that is matched against a reply from the Hyper-V
> +   host. Useful when the struct completion (or other rendezvous data)
> +   must reside on the caller's stack. By invalidating the transaction
> +   ID before exiting the function due to a timeout or other error, a
> +   late arriving interrupt is assured to not trash the stack.
> +3. vmbus_sendpacket_mpb_desc(): Message with one or more data ranges
> +   to target. Each range consists of a single offset and length plus
> +   a list of GPAs that describe a logical area of guest memory.
>
>  Historically, Linux guests have trusted Hyper-V to send well-formed
>  and valid messages, and Linux drivers for synthetic devices did not

Re: Patch "Documentation: hyperv: Update documentation for sending VMBus packets" has been added to the 6.12-stable tree

[Sasha Levin]

> This patch should not be backported to earlier than 6.15, as
> vmbus_sendpacket_pagebuffer() was removed in 6.15.

Thanks. The removal of vmbus_sendpacket_pagebuffer() (upstream 45a442fe369e)
was itself backported to stable: 6.12.100 (899e014e6847d), 6.6.100
(6d2d375205455) and 6.1.140 (763db1b8b0036). Those trees no longer have the
function, so the documentation update matches them and I'm keeping the patch
in 6.12, 6.6 and 6.1.

Your note covered all three trees. Could you confirm that keeping it there is
fine?

-- 
Thanks,
Sasha