This series addresses bug fixes across KVM PPC Book3S HV
locking/synchronization and paired-single instruction decoding.
Patches 1 & 2 fix synchronization and preemption issues introduced in
commit 6165d5dd99db ("KVM: PPC: Book3S HV: add virtual mode handlers for
HPT hcalls and page faults"):
- Patch 1 adds SRCU read lock protection when walking memslots during
virtual-mode HPT hcalls to prevent use-after-free races with concurrent
memslot updates.
- Patch 2 adds preempt_disable() around all virtual-mode HPTE bit-lock
holders — both the guest vCPU paths (kvmppc_hpte_hv_fault() and
kvmppc_pseries_do_hpt_hcall()) and the host-side paths
(kvm_unmap_rmapp(), kvm_age_rmapp(), kvm_test_clear_dirty_npages(),
resize_hpt_rehash_hpte()) — to prevent CPU stalls and deadlocks on
preemption.
Patch 3 fixes paired-single D-form instruction emulation:
- Patch 3 fixes get_d_signext() to correctly extract the full 12-bit D
displacement field and perform proper two's-complement sign extension.
Testing:
========
All test kernel builds were compiled with CONFIG_DEBUG_ATOMIC_SLEEP=y.
The following scenarios were verified:
1. Power9 PowerNV (L0) in Radix mode:
- Booted L0 host with kernel containing all 3 patches.
- Booted KVM guests in both Radix and Hash modes.
- Ran kernel build workload inside guests — no errors observed.
- Booted L1 guest with the same kernel — booted and ran cleanly.
2. Power9 PowerNV (L0) in Hash mode:
- Booted L0 host with kernel containing all 3 patches.
- Booted KVM guest in Hash mode.
- Ran kernel build workload inside guest — no errors observed.
- Booted L1 nested guest with the same kernel — booted and ran cleanly.
3. Power10 LPAR (L1):
- Booted Power10 LPAR with the patched kernel.
- Booted KVM guest and ran workloads — no errors observed.
Changes in v2:
==============
- v1: https://lore.kernel.org/all/[email protected]/
- Patch 2: Extended preempt_disable()/preempt_enable() coverage to also wrap
the HPTE bit-lock hold windows in four host-side virtual-mode functions:
kvm_unmap_rmapp(), kvm_age_rmapp(), kvm_test_clear_dirty_npages(), and
resize_hpt_rehash_hpte(). These were identified as vulnerable by Sashiko AI
review and confirmed correct by audit.
- Dropped Reviewed-by from Ritesh as the patch was materially extended.
- Patch 2: Added warning comment above kvmppc_pseries_do_hpt_hcall()
documenting the preemption requirement.
Amit Machhiwal (3):
KVM: PPC: Book3S HV: Add SRCU protection for virtual-mode HPT hcalls
KVM: PPC: Book3S HV: Add preempt_disable() around virtual-mode HPTE
bit-lock users
KVM: PPC: Fix get_d_signext() 12-bit displacement for paired-single
D-form
arch/powerpc/kvm/book3s_64_mmu_hv.c | 12 ++++
arch/powerpc/kvm/book3s_hv.c | 80 +++++++++++++-----------
arch/powerpc/kvm/book3s_paired_singles.c | 7 +--
3 files changed, 58 insertions(+), 41 deletions(-)
base-commit: 551c722f40809618230001baccf219193e22fc5a
--
2.54.0 (Apple Git-157)
