[PATCH] KVM: selftests: arm64: Add test for cross-vCPU LPI disable race

[Yuchao Zhang]

Thanks for the Sashiko review. All three points are legitimate; v2 addresses them:

1. INVALL/SYNC on unmapped collection:
Agreed - INVALL for collection 1 was a command error that stalls the
virtual ITS queue. v2 only sends INVALL and SYNC for TARGET_VCPU_ID
(the only mapped collection and the only vCPU receiving ITS commands);
unmapped collections and untouched vCPUs are skipped.

2. configure_lpis() overflow via -e:
Agreed. v2 bounds-checks the -e argument in main() (must fit in one 64K
ITT page) and adds an explicit assertion in configure_lpis() that
nr_lpis <= SZ_64K to guarantee the property table is never overrun.

3. Silently ignored KVM_SIGNAL_MSI failures:
Agreed in spirit. Injection failures are expected during the brief
window where the disable path has invalidated the ITS caches and the
guest has not yet remapped them. v2 counts successful injections
(checking KVM_SIGNAL_MSI return value > 0) and asserts at the end
that at least one succeeded, so a permanently broken environment can
no longer yield a false pass.

Additionally, v2 re-establishes the ITS mappings after every
EnableLPIs toggle. Without this, the disable path's cache invalidation
kills all mappings after the first iteration and the MSI flood goes
silent - now the overflow window exists on every iteration, matching
the re-initialisation sequence a real guest performs on re-enable.

Tested status is unchanged: no KVM-capable hardware available, so
compile- and TCG-plumbing-tested only; no Tested-by.

pw-bot: cr

Thanks,
Yuchao