mshv: limit SynIC management to MSHV-owned resources

The SynIC is shared between VMBus and MSHV. VMBus owns the message
page (SIMP), event flags page (SIEFP), global enable (SCONTROL),
and SINT2. MSHV adds SINT0, SINT5, and the event ring page (SIRBP).

Currently mshv_synic_cpu_init() redundantly enables SIMP, SIEFP, and
SCONTROL that VMBus already configured, and mshv_synic_cpu_exit()
disables all of them. This is wrong because MSHV can be torn down
while VMBus is still active. In particular, a kexec reboot notifier
tears down MSHV first. Disabling SCONTROL, SIMP, and SIEFP out
from under VMBus causes its later cleanup to write SynIC MSRs while
SynIC is disabled, which the hypervisor does not tolerate.

Restrict MSHV to managing only the resources it owns:
- SINT0, SINT5: mask on cleanup, unmask on init
- SIRBP: enable/disable as before
- SIMP, SIEFP, SCONTROL: leave to VMBus when it is active (L1VH
  and nested root partition); on a non-nested root partition VMBus
  does not run, so MSHV must enable/disable them

While here, fix the SIEFP and SIRBP memremap() and virt_to_phys()
calls to use HV_HYP_PAGE_SHIFT/HV_HYP_PAGE_SIZE instead of
PAGE_SHIFT/PAGE_SIZE. The hypervisor always uses 4K pages for SynIC
register GPAs regardless of the kernel page size, so using PAGE_SHIFT
produces wrong addresses on ARM64 with 64K pages.

Note that initialization order matters - VMBUS first, MSHV second,
and the reverse on de-init. Ideally, we would want a dedicated SYNIC
driver that replaces the cross-dependencies with a clear API and
dynamic tracking. Such refactor should go into its own dedicated
series, outside of this kexec fix series.

Signed-off-by: Jork Loeser <jloeser@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Reviewed-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

0 files changed, 0 insertions, 0 deletions