Subject: [PATCH v2 00/15] Add arm64 support in MSHV_VTL

From: Naman Jain <[email-masked]>
Date: Thu, 23 Apr 2026 12:41:50 +0000

The series adds support for ARM64 to mshv_vtl driver.
For this, common Hyper-V code is refactored, necessary support is added,
mshv_vtl_main.c is refactored and then finally support is added in
Kconfig.

Changes since v1:
https://lore.kernel.org/all/[email-masked]/

Patch 1: arm64: smp: Export arch_smp_send_reschedule for mshv_vtl module
* Changed prefix in subject (Michael)
* Sashiko - no issues

Patch 2:
* Add #include <linux/io.h> in hv_common.c (Michael)
* Remove ms_hyperv.hints change from non TDX case,
  as it won't matter in failure case (Michael)
* Add ms_hyperv.hints &=
  ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED for TDX
  case, to maintain parity with existing code.
  (Sashiko)
* Handle synic_eventring_tail -ENOMEM issue by
  returning early (Michael|Sashiko)
* Only 4k page is used here, so add dependency on
  PAGE_SIZE_4KB for MSHV_VTL as well in a later
  Kconfig patch (Sashiko|Michael)
* Use HV_HYP_PAGE_SIZE instead of PAGE_SIZE to avoid
  page size mismatch issues (Sashiko)
* s/"vmalloc_to_pfn(*hvp)"/
  "page_to_hvpfn(vmalloc_to_page(*hvp))" in
  hv_common.c (Sashiko|Michael)
* s/GFP_KERNEL/flags in __vmalloc. (Sashiko|Michael)
* Limit code to 80 lines in hv_common_cpu_init (Mukesh R.)
* Move arch based definition of
  HV_VP_ASSIST_PAGE_ADDRESS_SHIFT to
  hvgdk_mini.h (Michael)
* Added a comment about x64 vmalloc_to_pfn(*hvp)) (Michael)
* Move remaining hv_vp_assist_page code from
  arch/x86/include/asm/mshyperv.h to
  include/asm-generic/mshyperv.h (Michael)
* s/HV_SYN_REG_VP_ASSIST_PAGE/HV_MSR_VP_ASSIST_PAGE (Michael)

Patch 3:
* Rework the code and remove these new APIs. Move
  the vmbus_handler global variable and
  hv_setup_vmbus_handler()/hv_remove_vmbus_handler()
  from arch/x86 to drivers/hv/hv_common.c so that
  the same APIs can be used to setup per-cpu vmbus
  handlers as well for arm64. (Michael)

Patch 4:
* Sashiko's comments are generic and outside the
  scope of the refactoring this patch is doing.
  Will take it up separately.

Patch 6:
* Sashiko's comment regarding race condition is false positive.
* Regarding memory leak on cpu offline - online -
  beyond the scope of this series, I will fix it
  separately.

Patch 7:
* Subject s/"arch: arm64:"/"arm64: hyperv:" (Michael)
* Changed commit msg as per Michael's suggestion
* Add kernel_neon_begin(), kernel_neon_end() calls (Sashiko)
* Removed Note prefix from comments (Michael)
* Added compile time check for cpu context to be
  within 1024 bytes of mshv_vtl_run
* Moved the declarations of mshv_vtl_return_call to generic file

Patch 8:
* Split the patch into three patches - number 8-10 (Michael)
* Moved hv_vtl_configure_reg_page declaration to asm-generic header
* Sashiko's other reviews are for existing code,
  I will take them separately

Patch 9: (now patch 11)
No changes required for Sashiko's comments as most
of such controls are intentionally designated to
OpenVMM to keep kernel driver simpler.

Patch 10: (now patch 13)
* Remove hv_setup_percpu_vmbus_handler invocations,
  after redesign in previous patchsets (Michael)
* Simplified mshv_vtl_get_vsm_regs() by moving arch
  specific code (for x86) to hv_vtl -
  mshv_vtl_return_call_init(). This removes arch
  checks in mshv_vtl driver. Add a separate patch
  for this (now patch 12)
* Other Sachiko's reviews are related to existing
  code - can be taken up separately

Patch 11 (now patch 15):
* Only 4k page is supported, so add dependency on
  PAGE_SIZE_4KB for MSHV_VTL (Sashiko|Mihael)
* Remove "Kconfig: " from subject line. (Michael)

New patch 14:
Add a Kconfig dependency on 4K PAGE_SIZE for
MSHV_VTL to manage assumptions in MSHV_VTL driver

Change prefix in subjects as per below naming convention:
mshv_vtl_main changes - "mshv_vtl: "
arch/arm64 Hyper-V changes - "arm64: hyperv: "
arch/x86 Hyper-V changes - "x86/hyperv: "

Add Reviewed-by on already reviewed patches.

Naman Jain (15):
  arm64: smp: Export arch_smp_send_reschedule for mshv_vtl module
  Drivers: hv: Move hv_vp_assist_page to common files
  Drivers: hv: Move vmbus_handler to common code
  mshv_vtl: Refactor the driver for ARM64 support to be added
  Drivers: hv: Export vmbus_interrupt for mshv_vtl module
  mshv_vtl: Make sint vector architecture neutral
  arm64: hyperv: Add support for mshv_vtl_return_call
  Drivers: hv: Move hv_call_(get|set)_vp_registers() declarations
  Drivers: hv: mshv_vtl: Move hv_vtl_configure_reg_page() to x86
  arm64: hyperv: Add hv_vtl_configure_reg_page() stub
  mshv_vtl: Let userspace do VSM configuration
  mshv_vtl: Move VSM code page offset logic to x86 files
  mshv_vtl: Add remaining support for arm64
  Drivers: hv: Add 4K page dependency in MSHV_VTL
  Drivers: hv: Add ARM64 support for MSHV_VTL in Kconfig

 arch/arm64/hyperv/Makefile        |   1 +
 arch/arm64/hyperv/hv_vtl.c        | 165 ++++++++++++++++++++++++
 arch/arm64/include/asm/mshyperv.h |  25 ++++
 arch/arm64/kernel/smp.c           |   1 +
 arch/x86/hyperv/hv_init.c         |  88 +------------
 arch/x86/hyperv/hv_vtl.c          | 149 ++++++++++++++++++++-
 arch/x86/include/asm/mshyperv.h   |  21 +--
 arch/x86/kernel/cpu/mshyperv.c    |  12 --
 drivers/hv/Kconfig                |   7 +-
 drivers/hv/hv_common.c            | 103 ++++++++++++++-
 drivers/hv/mshv.h                 |   8 --
 drivers/hv/mshv_vtl.h             |   3 +
 drivers/hv/mshv_vtl_main.c        | 208 +++---------------------------
 drivers/hv/vmbus_drv.c            |  18 +--
 include/asm-generic/mshyperv.h    |  62 +++++++++
 include/hyperv/hvgdk_mini.h       |   6 +-
 16 files changed, 550 insertions(+), 327 deletions(-)
 create mode 100644 arch/arm64/hyperv/hv_vtl.c

-- 
2.43.0