cpu->exit_request is used to kick vCPU threads into qemu_wait_io_event().
The code that handles the signaling of cpu->exit_request is messy, mostly
due to no one ever taking a look at it as a whole. In fact already in commit
4b8523ee896 ("kvm: First step to push iothread lock out of inner run loop",
2015-07-01), the read of cpu->exit_request was placed outside the BQL
critical section without much attention to ordering; and it only got
worse from that point, in no small part due to a young and naive me.
This series is complementary to the cpu->interrupt_request cleanups
that Igor did in "memory: reintroduce BQL-free fine-grained PIO/MMIO"
(https://lore.kernel.org/qemu-devel/20250808120137.2208800-1-imamm...@redhat.com/T/),
and is organized like this:
- patches 1-3 clean up accesses to the variable to properly use
qatomic_* accessors
- patches 4-6 makes it possible to use cpu_exit() for all accelerators
- patch 7 removes from user-mode emulation a hack that is only needed
by system emulation
- patch 8 cleans up the way in which exit_request is cleared.
Paolo
Paolo Bonzini (8):
accel: use store_release/load_acquire for cross-thread exit_request
accel/hvf: check exit_request before running the vCPU
accel: use atomic accesses for exit_request
accel/tcg: introduce tcg_kick_vcpu_thread
cpus: remove TCG-ism from cpu_exit()
cpus: properly kick CPUs out of inner execution loop
tcg/user: do not set exit_request gratuitously
accel: make all calls to qemu_wait_io_event look the same
docs/devel/tcg-icount.rst | 2 +-
accel/tcg/tcg-accel-ops-mttcg.h | 3 ---
include/exec/cpu-common.h | 1 +
accel/dummy-cpus.c | 2 +-
accel/hvf/hvf-accel-ops.c | 2 +-
accel/kvm/kvm-accel-ops.c | 3 ++-
accel/kvm/kvm-all.c | 21 +++++++---------
accel/tcg/cpu-exec.c | 27 +++++++++++++++++---
accel/tcg/tcg-accel-ops-mttcg.c | 12 ++-------
accel/tcg/tcg-accel-ops-rr.c | 42 ++++++++++++++++---------------
accel/tcg/tcg-accel-ops.c | 4 +--
bsd-user/main.c | 2 +-
cpu-common.c | 3 ++-
hw/core/cpu-common.c | 7 +++---
hw/ppc/ppc.c | 2 ++
hw/ppc/spapr_hcall.c | 7 +++---
hw/ppc/spapr_rtas.c | 2 +-
linux-user/main.c | 2 +-
replay/replay-events.c | 3 ++-
system/cpu-timers.c | 6 ++---
system/cpus.c | 6 +++--
target/arm/hvf/hvf.c | 3 +++
target/arm/tcg/mte_helper.c | 2 +-
target/i386/hvf/hvf.c | 3 +++
target/i386/kvm/hyperv.c | 1 -
target/i386/kvm/kvm.c | 2 +-
target/i386/nvmm/nvmm-accel-ops.c | 8 +++---
target/i386/nvmm/nvmm-all.c | 9 +++----
target/i386/whpx/whpx-accel-ops.c | 6 ++---
target/i386/whpx/whpx-all.c | 11 ++++----
30 files changed, 106 insertions(+), 98 deletions(-)
--
2.50.1
