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8539093919
I missed the fact that when an exclusive work item runs it drops the BQL to ensure all no vCPUs are stuck waiting for it, hence causing a deadlock. However the actual helper needs to take the BQL especially as we'll be messing with device emulation bits during the update which all assume BQL is held. We make a minor cpu_reloading_memory_map which must try and unlock the RCU if we are actually outside the running context. Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
83 lines
2.8 KiB
C
83 lines
2.8 KiB
C
/*
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* emulator main execution loop
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*
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* Copyright (c) 2003-2005 Fabrice Bellard
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include "qemu/osdep.h"
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#include "cpu.h"
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#include "sysemu/cpus.h"
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#include "exec/exec-all.h"
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#include "exec/memory-internal.h"
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/* exit the current TB, but without causing any exception to be raised */
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void cpu_loop_exit_noexc(CPUState *cpu)
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{
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/* XXX: restore cpu registers saved in host registers */
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cpu->exception_index = -1;
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siglongjmp(cpu->jmp_env, 1);
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}
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#if defined(CONFIG_SOFTMMU)
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void cpu_reloading_memory_map(void)
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{
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if (qemu_in_vcpu_thread() && current_cpu->running) {
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/* The guest can in theory prolong the RCU critical section as long
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* as it feels like. The major problem with this is that because it
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* can do multiple reconfigurations of the memory map within the
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* critical section, we could potentially accumulate an unbounded
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* collection of memory data structures awaiting reclamation.
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*
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* Because the only thing we're currently protecting with RCU is the
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* memory data structures, it's sufficient to break the critical section
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* in this callback, which we know will get called every time the
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* memory map is rearranged.
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*
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* (If we add anything else in the system that uses RCU to protect
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* its data structures, we will need to implement some other mechanism
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* to force TCG CPUs to exit the critical section, at which point this
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* part of this callback might become unnecessary.)
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*
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* This pair matches cpu_exec's rcu_read_lock()/rcu_read_unlock(), which
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* only protects cpu->as->dispatch. Since we know our caller is about
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* to reload it, it's safe to split the critical section.
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*/
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rcu_read_unlock();
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rcu_read_lock();
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}
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}
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#endif
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void cpu_loop_exit(CPUState *cpu)
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{
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siglongjmp(cpu->jmp_env, 1);
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}
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void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc)
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{
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if (pc) {
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cpu_restore_state(cpu, pc);
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}
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siglongjmp(cpu->jmp_env, 1);
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}
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void cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc)
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{
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cpu->exception_index = EXCP_ATOMIC;
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cpu_loop_exit_restore(cpu, pc);
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}
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