As suggested in https://bugzilla.redhat.com/show_bug.cgi?id=1952483#c16 I open a BZ against Clang to follow the issue of 'lto' with qemu's coroutines.

The issue was first found with 'lto' option along with gcc. It looks the issue still is there with clang using lto option, at least on ARM.  https://bugzilla.redhat.com/show_bug.cgi?id=1952483#c15 suggests it seems to work on s390x though (to be confirmed).

A technical analysis of the issue from the qemu perspective can be found at
https://bugzilla.redhat.com/show_bug.cgi?id=1952483#c8

Florian Weimer started a thread upstream
Disabling TLS address caching to help QEMU on GNU/Linux
https://gcc.gnu.org/pipermail/gcc/2021-July/236831.html

Same kind of discussion shall happen for CLANG I guess.

How to reproduce, configure & build qemu with clang and lto.

./configure --cc=clang --cxx=/bin/false --prefix=/usr --libdir=/usr/lib64 --datadir=/usr/share --sysconfdir=/etc --interp-prefix=/usr/qemu-%M --localstatedir=/var --docdir=/usr/share/doc --libexecdir=/usr/libexec '--extra-ldflags=-Wl,-z,relro -Wl,--as-needed  -Wl,-z,now   -flto' '--extra-cflags=-O2 -flto -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS --config /usr/lib/rpm/redhat/redhat-hardened-clang.cfg -fstack-protector-strong   -fasynchronous-unwind-tables ' --target-list=aarch64-softmmu --enable-kvm --extra-cflags=-Wstrict-prototypes --extra-cflags=-Wredundant-decls --enable-trace-backends=log --enable-seccomp --enable-cap-ng --disable-werror --without-default-devices --disable-capstone --meson=/usr/bin/meson
make
sudo dnf -y install perl-Test-Harness
make check-unit -j8

test-block-iothread during "make check " fails on aarch64 with ERROR test-block-iothread - Bail out! ERROR:../tests/unit/test-block-iothread.c:379:test_job_run: assertion failed: (qemu_get_current_aio_context() == job->aio_context)

Normally test-block-iothread  shall pass.