Fix guest_memfd bugs related to binding to a memslot:
- Handle errors when inserting into guest_memfd's binding xarray, e.g. to
do the right thing on ENOMEM.
- Bind a memslot only once the memslot is fully prepared (because it becomes
reachable/visible once its inserted into gmem's bindings arraxy).
Patch 5 is a related cleanup to remove a superflous WRITE_ONCE() (unwinding
the slot update on insertion failure isn't an option if the slot is observable,
i.e. if the WRITE_ONCE() is actually necessary).
v4:
- Drop intermediate xar variable. [David, Ackerley]
- Collect reviews. [David, Ackerley]
- Restrict kvm_gmem_bind() to CREATE as calling kvm_arch_free_memslot() on
FLAGS_ONLY changes is unsafe, and doing the right thing for dirty bitmaps
is tricky for similar reasons. As a bonus, this eliminates the ugly
almost-duplicate code that David pointed out.
- Explain why KVM must deal with the unwind during bind(). [Ackerley]
v3:
- https://lore.kernel.org/all/20260904004342.3162959-1-seanjc@google.com
- Nullify bindings on error before dropping invalidat lock. [Sashiko x3]
v2:
- https://lore.kernel.org/all/20260902182020.2615443-1-seanjc@google.com
- Fix the binding-too-early bug. [Sashiko]
- Explicitly zero the bindings entry on failure to ensure there are no
partial entries. [Sashiko]
v1: https://lore.kernel.org/all/20260826165154.766699-2-seanjc@google.com
Sean Christopherson (5):
KVM: guest_memfd: Gracefully handle xarray errors when binding a
memslot
KVM: Use goto to handle errors during memslot preparation
KVM: Only bind memslot to guest_memfd instance for CREATE operations
KVM: guest_memfd: Establish memslot<=>guest_memfd bindings *after*
memslot is ready
KVM: guest_memfd: Drop superfluous WRITE_ONCE() when binding a memslot
virt/kvm/guest_memfd.c | 14 ++++++++--
virt/kvm/kvm_main.c | 62 ++++++++++++++++++++++--------------------
2 files changed, 44 insertions(+), 32 deletions(-)
base-commit: 70c944caf570fda2d79baa71435589a8db39f048
--
2.55.0.1082.g2b9226bbc0-goog