[PATCH v4 0/3] Hyper-V: kexec fixes for L1VH (mshv)

Jork Loeser
2026-04-27T21:39:03Z

This series fixes kexec support when Linux runs as an L1 Virtual Host
(L1VH) under Hyper-V, using the MSHV driver to manage child VMs.

1-2. SynIC cleanup: the MSHV driver manages its own SynIC resources
separately from vmbus. Add proper teardown of MSHV-owned SINTs
and SIRBP on kexec, scoped to only the resources MSHV owns.
Use hv_vmbus_exists() to decide at runtime whether VMBus owns
SIMP/SIEFP/SCONTROL (so MSHV must not touch them) or whether
MSHV must manage them itself (bare root partition without VMBus).
Also fix SIEFP and SIRBP address calculations to use
HV_HYP_PAGE_SHIFT instead of PAGE_SHIFT, which produces wrong
addresses on ARM64 with 64K pages.

3. Debugfs stats pages: unmap the VP statistics overlay pages before
kexec to avoid machine check exceptions when the new kernel
reuses those physical pages.

Changes since v3:
- Dropped patches 1-3 (vmbus variable shadowing, stimer cleanup,
LP/VP skip), now merged via hyperv-next.
- Patch 1: fix SIEFP and SIRBP memremap()/virt_to_phys() to use
HV_HYP_PAGE_SHIFT/HV_HYP_PAGE_SIZE instead of PAGE_SHIFT/PAGE_SIZE.

Changes since v2:
- Rebased onto linux-next/master to adapt to the upstream SynIC
refactor (commit 5a674ef871fe, "mshv: refactor synic init and
cleanup").

Changes since v1:
- Patch 1: account for nested root partitions where VMBus is also
active (not just L1VH); use a vmbus_active local variable; allocate
SIRBP in L1VH allocation path for when the hypervisor doesn't
pre-provision the page.

Jork Loeser (3):
mshv: limit SynIC management to MSHV-owned resources
mshv: clean up SynIC state on kexec for L1VH
mshv: unmap debugfs stats pages on kexec

drivers/hv/hv.c | 3 +
drivers/hv/mshv_debugfs.c | 7 +-
drivers/hv/mshv_synic.c | 154 +++++++++++++++++++++++++-------------
3 files changed, 110 insertions(+), 54 deletions(-)

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2.43.0