On Thu, 06/18 18:47, Paolo Bonzini wrote:
> From: Jan Kiszka <jan.kis...@siemens.com>
>
> This opens the path to get rid of the iothread lock on vmexits in KVM
> mode. On x86, the in-kernel irqchips has to be used because we otherwise
> need to synchronize APIC and other per-cpu state accesses that could be
> changed concurrently.
>
> s390x and ARM should be fine without specific locking as their
> pre/post-run callbacks are empty. MIPS and POWER require locking for
> the pre-run callback.
>
> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> kvm-all.c | 14 ++++++++++++--
> target-i386/kvm.c | 18 ++++++++++++++++++
> target-mips/kvm.c | 4 ++++
> target-ppc/kvm.c | 4 ++++
> 4 files changed, 38 insertions(+), 2 deletions(-)
>
> diff --git a/kvm-all.c b/kvm-all.c
> index b2b1bc3..2bd8e9b 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -1795,6 +1795,8 @@ int kvm_cpu_exec(CPUState *cpu)
> return EXCP_HLT;
> }
>
> + qemu_mutex_unlock_iothread();
> +
> do {
> MemTxAttrs attrs;
>
> @@ -1813,11 +1815,9 @@ int kvm_cpu_exec(CPUState *cpu)
> */
> qemu_cpu_kick_self();
> }
> - qemu_mutex_unlock_iothread();
>
> run_ret = kvm_vcpu_ioctl(cpu, KVM_RUN, 0);
>
> - qemu_mutex_lock_iothread();
> attrs = kvm_arch_post_run(cpu, run);
>
> if (run_ret < 0) {
> @@ -1836,20 +1836,24 @@ int kvm_cpu_exec(CPUState *cpu)
> switch (run->exit_reason) {
> case KVM_EXIT_IO:
> DPRINTF("handle_io\n");
> + qemu_mutex_lock_iothread();
> kvm_handle_io(run->io.port, attrs,
> (uint8_t *)run + run->io.data_offset,
> run->io.direction,
> run->io.size,
> run->io.count);
> + qemu_mutex_unlock_iothread();
> ret = 0;
> break;
> case KVM_EXIT_MMIO:
> DPRINTF("handle_mmio\n");
> + qemu_mutex_lock_iothread();
> address_space_rw(&address_space_memory,
> run->mmio.phys_addr, attrs,
> run->mmio.data,
> run->mmio.len,
> run->mmio.is_write);
> + qemu_mutex_unlock_iothread();
> ret = 0;
> break;
> case KVM_EXIT_IRQ_WINDOW_OPEN:
> @@ -1858,7 +1862,9 @@ int kvm_cpu_exec(CPUState *cpu)
> break;
> case KVM_EXIT_SHUTDOWN:
> DPRINTF("shutdown\n");
> + qemu_mutex_lock_iothread();
> qemu_system_reset_request();
> + qemu_mutex_unlock_iothread();
> ret = EXCP_INTERRUPT;
> break;
> case KVM_EXIT_UNKNOWN:
More context:
fprintf(stderr, "KVM: unknown exit, hardware reason %" PRIx64 "\n",
(uint64_t)run->hw.hardware_exit_reason);
ret = -1;
break;
case KVM_EXIT_INTERNAL_ERROR:
* ret = kvm_handle_internal_error(cpu, run);
break;
case KVM_EXIT_SYSTEM_EVENT:
switch (run->system_event.type) {
case KVM_SYSTEM_EVENT_SHUTDOWN:
* qemu_system_shutdown_request();
ret = EXCP_INTERRUPT;
break;
case KVM_SYSTEM_EVENT_RESET:
* qemu_system_reset_request();
ret = EXCP_INTERRUPT;
> break;
> default:
> DPRINTF("kvm_arch_handle_exit\n");
> + qemu_mutex_lock_iothread();
> ret = kvm_arch_handle_exit(cpu, run);
> + qemu_mutex_unlock_iothread();
> break;
> }
> } while (ret == 0);
>
> + qemu_mutex_lock_iothread();
> +
> if (ret < 0) {
> cpu_dump_state(cpu, stderr, fprintf, CPU_DUMP_CODE);
> vm_stop(RUN_STATE_INTERNAL_ERROR);
Could you explain why above three "*" calls are safe?
Fam
