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| author | Uros Bizjak <ubizjak@gmail.com> | 2023-04-25 14:39:32 +0300 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2023-05-26 21:24:52 +0300 |
| commit | 12ced095956a517dc0c8c8f9264e29fd67124302 (patch) | |
| tree | 4d69035b8f68b754ac9092ad5a5a270e405fb897 /arch/x86/kvm/mmu/tdp_mmu.c | |
| parent | b9846a698c9aff4eb2214a06ac83638ad098f33f (diff) | |
| download | linux-12ced095956a517dc0c8c8f9264e29fd67124302.tar.xz | |
KVM: x86/mmu: Add comment on try_cmpxchg64 usage in tdp_mmu_set_spte_atomic
Commit aee98a6838d5 ("KVM: x86/mmu: Use try_cmpxchg64 in
tdp_mmu_set_spte_atomic") removed the comment that iter->old_spte is
updated when different logical CPU modifies the page table entry.
Although this is what try_cmpxchg does implicitly, it won't hurt
if this fact is explicitly mentioned in a restored comment.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: David Matlack <dmatlack@google.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Link: https://lore.kernel.org/r/20230425113932.3148-1-ubizjak@gmail.com
[sean: extend comment above try_cmpxchg64()]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/kvm/mmu/tdp_mmu.c')
| -rw-r--r-- | arch/x86/kvm/mmu/tdp_mmu.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 08340219c35a..512163d52194 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -592,7 +592,10 @@ static inline int tdp_mmu_set_spte_atomic(struct kvm *kvm, /* * Note, fast_pf_fix_direct_spte() can also modify TDP MMU SPTEs and - * does not hold the mmu_lock. + * does not hold the mmu_lock. On failure, i.e. if a different logical + * CPU modified the SPTE, try_cmpxchg64() updates iter->old_spte with + * the current value, so the caller operates on fresh data, e.g. if it + * retries tdp_mmu_set_spte_atomic() */ if (!try_cmpxchg64(sptep, &iter->old_spte, new_spte)) return -EBUSY; |