KVM: arm64: Return -EINVAL for an empty SMCCC filter range at base 0

kvm_smccc_set_filter() only rejects a range if its inclusive end,
base + nr_functions - 1, is below base. That catches an empty range
(nr_functions == 0) at every nonzero base, but at base 0 the end wraps
to U32_MAX and KVM tries to insert [0, U32_MAX], which overlaps the
reserved Arm Architecture Calls ranges. KVM_ARM_VM_SMCCC_FILTER then
returns -EEXIST instead of the -EINVAL that the smccc_filter selftest
expects for an empty range.

Reject a zero function count explicitly.

Tested with a userspace reproducer on an arm64 VHE host under QEMU TCG:
EEXIST before, EINVAL after.

Fixes: 821d935c87bc ("KVM: arm64: Introduce support for userspace SMCCC filtering")
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Tested-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20260829054856.70549-2-kmehltretter@gmail.com
Signed-off-by: Oliver Upton <oupton@kernel.org>

0 files changed, 0 insertions, 0 deletions