[PATCH v2 1/4] KVM: PPC: Book3S HV: Ensure that calls to idr_alloc are synchronized
flat view
WARM1d
From: Gautam Menghani <hidden>
Date: 2026-10-09 12:31:10
Also in:
kvm, lkml, stable
Subsystem:
kernel virtual machine for powerpc (kvm/powerpc), linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
Revision v2 of 2 in this series.
Revisions (2)
- v1 [diff vs current]
- v2 current
Calls to idr_alloc() in __prealloc_nested() are not currently synchronized.
According to the documentation [1], the caller should provide their own
locking to prevent concurrent modifications to the idr to prevent bugs.
Wrap the call to __prealloc_nested() in a spinlock to prevent concurrent
modifications to idr.
[1]: lib/idr.c
Fixes: c0f00a18e2a8 ("KVM: PPC: Book3S HV Nested: Change nested guest lookup to use idr")
Cc: stable@vger.kernel.org # 5.19+
Co-developed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Gautam Menghani <redacted>
---
arch/powerpc/kvm/book3s_hv_nested.c | 34 +++++++++--------------------
1 file changed, 10 insertions(+), 24 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
index a6ff42d7666c..e893fdd24f0a 100644
--- a/arch/powerpc/kvm/book3s_hv_nested.c
+++ b/arch/powerpc/kvm/book3s_hv_nested.c@@ -702,20 +702,6 @@ static struct kvm_nested_guest *__find_nested(struct kvm *kvm, int lpid) return idr_find(&kvm->arch.kvm_nested_guest_idr, lpid); } -static bool __prealloc_nested(struct kvm *kvm, int lpid) -{ - if (idr_alloc(&kvm->arch.kvm_nested_guest_idr, - NULL, lpid, lpid + 1, GFP_KERNEL) != lpid) - return false; - return true; -} - -static void __add_nested(struct kvm *kvm, int lpid, struct kvm_nested_guest *gp) -{ - if (idr_replace(&kvm->arch.kvm_nested_guest_idr, gp, lpid)) - WARN_ON(1); -} - static void __remove_nested(struct kvm *kvm, int lpid) { idr_remove(&kvm->arch.kvm_nested_guest_idr, lpid);
@@ -862,21 +848,21 @@ struct kvm_nested_guest *kvmhv_get_nested(struct kvm *kvm, int l1_lpid, if (!newgp) return NULL; - if (!__prealloc_nested(kvm, l1_lpid)) { - kvmhv_release_nested(newgp); - return NULL; - } - + idr_preload(GFP_KERNEL); spin_lock(&kvm->mmu_lock); gp = __find_nested(kvm, l1_lpid); if (!gp) { - __add_nested(kvm, l1_lpid, newgp); - ++newgp->refcnt; - gp = newgp; - newgp = NULL; + if (idr_alloc(&kvm->arch.kvm_nested_guest_idr, newgp, + l1_lpid, l1_lpid + 1, GFP_NOWAIT) >= 0) { + ++newgp->refcnt; + gp = newgp; + newgp = NULL; + } } - ++gp->refcnt; + if (gp) + ++gp->refcnt; spin_unlock(&kvm->mmu_lock); + idr_preload_end(); if (newgp) kvmhv_release_nested(newgp);
--
2.55.0