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3c2611bac0
LLVM commit https://reviews.llvm.org/D143726 introduced hoistMinMax optimization that transformed (i < VIRTIO_MAX_SGS) && (i < out_sgs) into i < MIN(VIRTIO_MAX_SGS, out_sgs) and caused the verifier to stop recognizing such loop as bounded. Which resulted in the following test failure: libbpf: prog 'trace_virtqueue_add_sgs': BPF program load failed: Bad address libbpf: prog 'trace_virtqueue_add_sgs': -- BEGIN PROG LOAD LOG -- The sequence of 8193 jumps is too complex. verification time 789206 usec stack depth 56 processed 156446 insns (limit 1000000) max_states_per_insn 7 total_states 1746 peak_states 1701 mark_read 12 -- END PROG LOAD LOG -- libbpf: prog 'trace_virtqueue_add_sgs': failed to load: -14 libbpf: failed to load object 'loop6.bpf.o' Workaround the verifier limitation for now with inline asm that prevents this particular optimization. Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.