Re: [PATCH v6 00/10] Introduce /dev/mshv root partition driver

[Wei Liu]

On Fri, Mar 14, 2025 at 12:28:46PM -0700, Nuno Das Neves wrote:
> This series introduces support for creating and running guest virtual
> machines while running on the Microsoft Hypervisor[0] as root partition.
> This is done via an IOCTL interface accessed through /dev/mshv, similar to
> /dev/kvm. Another series introducing this support was previously posted in
> 2021[1], and versions 1-4 of this series were posted in 2023[2].
> 
> Patches 1-4 are small refactors and additions to Hyper-V code.
> Patches 5-6 just export some definitions needed by /dev/mshv.
> Patches 7-9 introduce some functionality and definitions in common code, that
> are specific to the driver.
> Patch 10 contains the driver code.
> 
> -----------------
> [0] "Hyper-V" is more well-known, but it really refers to the whole stack
>     including the hypervisor and other components that run in Windows
>     kernel and userspace.
> [1] Previous /dev/mshv patch series (2021) and discussion:
> https://lore.kernel.org/linux-hyperv/1632853875-20261-1-git-send-email-nunodasneves@xxxxxxxxxxxxxxxxxxx/
> [2] v4 (2023):
> https://lore.kernel.org/linux-hyperv/1696010501-24584-1-git-send-email-nunodasneves@xxxxxxxxxxxxxxxxxxx/
> 
> -----------------
> Changes since v5:
> * Rework patch 1:
>  1. Introduce hv_status_printk() logging macros which print the raw HV_STATUS_
>     code along with string [Roman Kisel]
>  2. Iterate over an array of data items to get the string and errno for the
>     hv_result_to_*() functions. [Michael Kelley]
>  3. Use hv_status_printk() to log errors in hyperv/irqdomain.c and
>     hyperv-iommu.c [Easwar Hariharan]
> * Minor cleanup, improvements, and commit wording changes in patches 2, 3, 4, 6
>   [Roman Kisel, Easwar Hariharan, Michael Kelley]
> * Fix issues with declaration and lifecycle of hv_synic_eventring_tail in patch
>   7 [Michael Kelley]
> * Improve detail and clarity of commit message in patch 8 [Michael Kelley]
> * Minor cleanups in patch 9 - uapi types -> kernel types, #ifdef CONFIG_X86_64
>   -> CONFIG_X86 for consistency, fix HVCALL_* ordering, remove redundant
>   __packed, use explicit enum value [Stanislav Kinsburskii, Easwar Hariharan,
>   Michael Kelley, Tianyu Lan]
> * Minor fixes and cleanup in patch 10 [Michael Kelley]
> * Add MODULE_DESCRIPTION() to patch 10 [Jeff Johnson]
> 
> Changes since v4:
> * Slim down the IOCTL interface significantly, via several means:
>   1. Use generic "passthrough" call MSHV_ROOT_HVCALL to replace many ioctls.
>   2. Use MSHV_* versions of some of the HV_* definitions.
>   3. Move hv headers out of uapi altogether, into include/hyperv/, see:
> https://lore.kernel.org/linux-hyperv/1732577084-2122-1-git-send-email-nunodasneves@xxxxxxxxxxxxxxxxxxx/
> * Remove mshv_vtl module altogther, it will be posted in followup series
>   * Also remove the parent "mshv" module which didn't serve much purpose
> * Update and refactor parts of the driver code for clarity, extensibility
> 
> Changes since v3 (summarized):
> * Clean up the error and debug logging:
>   1. Add a set of macros vp_*() and partition_*() which call the equivalent
>      dev_*(), passing the device from the partition struct
>      * The new macros also print the partition and vp ids to aid debugging
> 	   and reduce repeated code
>   2. Use dev_*() (mostly via the new macros) instead of pr_*() *almost*
>   everywhere - in interrupt context we can't always get the device struct
>   3. Remove pr_*() logging from hv_call.c and mshv_root_hv_call.c
> 
> Changes since v2 (summarized):
> * Fix many checkpatch.pl --strict style issues
> * Initialize status in get/set registers hypercall helpers
> * Add missing return on error in get_vp_signaled_count
> 
> Changes since v1 (summarized):
> * Clean up formatting, commit messages
> 
> Nuno Das Neves (9):
>   hyperv: Log hypercall status codes as strings
>   arm64/hyperv: Add some missing functions to arm64
>   hyperv: Introduce hv_recommend_using_aeoi()
>   acpi: numa: Export node_to_pxm()
>   Drivers: hv: Export some functions for use by root partition module
>   Drivers: hv: Introduce per-cpu event ring tail
>   x86: hyperv: Add mshv_handler() irq handler and setup function
>   hyperv: Add definitions for root partition driver to hv headers
>   Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs
> 
> Stanislav Kinsburskii (1):
>   x86/mshyperv: Add support for extended Hyper-V features

Series applied to hyperv-next. Thanks.

I had to fix one minor compilation issue in patch 10, but nothing major.

I also folded the following patch to a previous patch that introduced
MSHV_ROOT (not in this series).


diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 794e88e9dc6b..3118d5472fab 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -57,7 +57,7 @@ config HYPERV_BALLOON
 
 config MSHV_ROOT
 	tristate "Microsoft Hyper-V root partition support"
-	depends on HYPERV
+	depends on HYPERV && (X86_64 || ARM64)
 	depends on !HYPERV_VTL_MODE
 	# The hypervisor interface operates on 4k pages. Enforcing it here
 	# simplifies many assumptions in the root partition code.

Wei.