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2017-04-10cpu-exec: update icount after each TB_EXITAlex Bennée
There is no particular reason we shouldn't update the global system icount time as we exit each TranslationBlock run. This ensures the main-loop doesn't have to wait until we exit to the outer loop for executed instructions to be credited to timer_state. The prepare_icount_for_run function is slightly tweaked to match the logic we run in cpu_loop_exec_tb. Based on Paolo's original suggestion. Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
2017-03-14qemu-timer: do not include sysemu/cpus.h from util/qemu-timer.hPaolo Bonzini
This dependency is the wrong way, and we will need util/qemu-timer.h from sysemu/cpus.h in the next patch. Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-03-03Merge branch 'icount-update' into HEADPaolo Bonzini
Merge the original development branch due to breakage caused by the MTTCG merge. Conflicts: cpu-exec.c translate-common.c Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-02-24cpu-exec: remove unnecessary check of cpu->exit_requestPaolo Bonzini
The cpu->exit_request check in cpu_loop_exec_tb is unnecessary, because cpu->tcg_exit_req is always set after cpu->exit_request. So let the TB exit and we will pick up the exit request later in cpu_handle_interrupt. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-02-24replay: check icount in cpu exec loopPavel Dovgalyuk
This patch adds check to break cpu loop when icount expires without setting the TB_EXIT_ICOUNT_EXPIRED flag. It happens when there is no available translated blocks and all instructions were executed. In icount replay mode unnecessary tb_find will be called (which may cause an exception) and execution will be non-deterministic. Because cpu_loop_exec_tb cannot longjmp anymore, we can remove the anticipated call to align_clocks in cpu_loop_exec_tb, as well as the SyncClocks *sc argument. Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru> Message-Id: <002801d2810f$18809c20$4981d460$@ru> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Pavel Dovgalyuk <dovgaluk@ispras.ru>
2017-02-24tcg: handle EXCP_ATOMIC exception for system emulationPranith Kumar
The patch enables handling atomic code in the guest. This should be preferably done in cpu_handle_exception(), but the current assumptions regarding when we can execute atomic sections cause a deadlock. The current mechanism discards the flags which were set in atomic execution. We ensure they are properly saved by calling the cc->cpu_exec_enter/leave() functions around the loop. As we are running cpu_exec_step_atomic() from the outermost loop we need to avoid an abort() when single stepping over atomic code since debug exception longjmp will point to the the setlongjmp in cpu_exec(). We do this by setting a new jmp_env so that it jumps back here on an exception. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> [AJB: tweak title, merge with new patches, add mmap_lock] Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> CC: Paolo Bonzini <pbonzini@redhat.com>
2017-02-24tcg: enable thread-per-vCPUAlex Bennée
There are a couple of changes that occur at the same time here: - introduce a single vCPU qemu_tcg_cpu_thread_fn One of these is spawned per vCPU with its own Thread and Condition variables. qemu_tcg_rr_cpu_thread_fn is the new name for the old single threaded function. - the TLS current_cpu variable is now live for the lifetime of MTTCG vCPU threads. This is for future work where async jobs need to know the vCPU context they are operating in. The user to switch on multi-thread behaviour and spawn a thread per-vCPU. For a simple test kvm-unit-test like: ./arm/run ./arm/locking-test.flat -smp 4 -accel tcg,thread=multi Will now use 4 vCPU threads and have an expected FAIL (instead of the unexpected PASS) as the default mode of the test has no protection when incrementing a shared variable. We enable the parallel_cpus flag to ensure we generate correct barrier and atomic code if supported by the front and backends. This doesn't automatically enable MTTCG until default_mttcg_enabled() is updated to check the configuration is supported. Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> [AJB: Some fixes, conditionally, commit rewording] Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net>
2017-02-24tcg: remove global exit_requestAlex Bennée
There are now only two uses of the global exit_request left. The first ensures we exit the run_loop when we first start to process pending work and in the kick handler. This is just as easily done by setting the first_cpu->exit_request flag. The second use is in the round robin kick routine. The global exit_request ensured every vCPU would set its local exit_request and cause a full exit of the loop. Now the iothread isn't being held while running we can just rely on the kick handler to push us out as intended. We lightly re-factor the main vCPU thread to ensure cpu->exit_requests cause us to exit the main loop and process any IO requests that might come along. As an cpu->exit_request may legitimately get squashed while processing the EXCP_INTERRUPT exception we also check cpu->queued_work_first to ensure queued work is expedited as soon as possible. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net>
2017-02-24tcg: drop global lock during TCG code executionJan Kiszka
This finally allows TCG to benefit from the iothread introduction: Drop the global mutex while running pure TCG CPU code. Reacquire the lock when entering MMIO or PIO emulation, or when leaving the TCG loop. We have to revert a few optimization for the current TCG threading model, namely kicking the TCG thread in qemu_mutex_lock_iothread and not kicking it in qemu_cpu_kick. We also need to disable RAM block reordering until we have a more efficient locking mechanism at hand. Still, a Linux x86 UP guest and my Musicpal ARM model boot fine here. These numbers demonstrate where we gain something: 20338 jan 20 0 331m 75m 6904 R 99 0.9 0:50.95 qemu-system-arm 20337 jan 20 0 331m 75m 6904 S 20 0.9 0:26.50 qemu-system-arm The guest CPU was fully loaded, but the iothread could still run mostly independent on a second core. Without the patch we don't get beyond 32206 jan 20 0 330m 73m 7036 R 82 0.9 1:06.00 qemu-system-arm 32204 jan 20 0 330m 73m 7036 S 21 0.9 0:17.03 qemu-system-arm We don't benefit significantly, though, when the guest is not fully loading a host CPU. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Message-Id: <1439220437-23957-10-git-send-email-fred.konrad@greensocs.com> [FK: Rebase, fix qemu_devices_reset deadlock, rm address_space_* mutex] Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com> [EGC: fixed iothread lock for cpu-exec IRQ handling] Signed-off-by: Emilio G. Cota <cota@braap.org> [AJB: -smp single-threaded fix, clean commit msg, BQL fixes] Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com> [PM: target-arm changes] Acked-by: Peter Maydell <peter.maydell@linaro.org>
2017-02-24tcg: rename tcg_current_cpu to tcg_current_rr_cpuAlex Bennée
..and make the definition local to cpus. In preparation for MTTCG the concept of a global tcg_current_cpu will no longer make sense. However we still need to keep track of it in the single-threaded case to be able to exit quickly when required. qemu_cpu_kick_no_halt() moves and becomes qemu_cpu_kick_rr_cpu() to emphasise its use-case. qemu_cpu_kick now kicks the relevant cpu as well as qemu_kick_rr_cpu() which will become a no-op in MTTCG. For the time being the setting of the global exit_request remains. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
2017-02-24mttcg: Add missing tb_lock/unlock() in cpu_exec_step()Pranith Kumar
The recent patch enabling lock assertions uncovered the missing lock acquisition in cpu_exec_step(). This patch adds them. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net>
2017-02-22cpu-exec: unify icount_decr and tcg_exit_reqPaolo Bonzini
The icount interrupt flag and tcg_exit_req serve almost the same purpose, let's make them completely the same. The former TB_EXIT_REQUESTED and TB_EXIT_ICOUNT_EXPIRED cases are unified, since we can distinguish them from the value of the interrupt flag. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-02-16target-i386: correctly propagate retaddr into SVM helpersPaolo Bonzini
Commit 2afbdf8 ("target-i386: exception handling for memory helpers", 2015-09-15) changed tlb_fill's cpu_restore_state+raise_exception_err to raise_exception_err_ra. After this change, the cpu_restore_state and raise_exception_err's cpu_loop_exit are merged into raise_exception_err_ra's cpu_loop_exit_restore. This actually fixed some bugs, but when SVM is enabled there is a second path from raise_exception_err_ra to cpu_loop_exit. This is the VMEXIT path, and now cpu_vmexit is called without a cpu_restore_state before. The fix is to pass the retaddr to cpu_vmexit (via cpu_svm_check_intercept_param). All helpers can now use GETPC() to pass the correct retaddr, too. Cc: qemu-stable@nongnu.org Fixes: 2afbdf84807d673eb682cb78158e11cdacbf4673 Reported-by: Alexander Boettcher <alexander.boettcher@genode-labs.com> Tested-by: Alexander Boettcher <alexander.boettcher@genode-labs.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-02-16cpu-exec: remove outermost infinite loopPaolo Bonzini
Reorganize the sigsetjmp so that the restart case falls through to cpu_handle_exception and the execution loop. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-02-16cpu-exec: avoid repeated sigsetjmp on interruptsPaolo Bonzini
The sigsetjmp only needs to be prepared once for the whole execution of cpu_exec. This patch takes care of the "== 0" side, using a nested loop so that cpu_handle_interrupt goes straight back to cpu_handle_exception without doing another sigsetjmp. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-02-16cpu-exec: avoid cpu_loop_exit in cpu_handle_interruptPaolo Bonzini
The siglongjmp goes straight back to the beginning of cpu_exec's outermost loop. We do not need a siglongjmp, we can simply leave the inner TB execution loop. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-02-16cpu-exec: tighten barrier on TCG_EXIT_REQUESTEDPaolo Bonzini
This seems to have worked just fine so far on weakly-ordered architectures, but I don't see anything that prevents the reordering from: store 1 to exit_request store 1 to tcg_exit_req load tcg_exit_req store 0 to tcg_exit_req load exit_request store 0 to exit_request store 1 to exit_request store 1 to tcg_exit_req to this: store 1 to exit_request store 1 to tcg_exit_req load tcg_exit_req load exit_request store 1 to exit_request store 1 to tcg_exit_req store 0 to tcg_exit_req store 0 to exit_request therefore losing a request. It's possible that other memory barriers (e.g. in rcu_read_unlock) are hiding it, but better safe than sorry. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-02-16cpu-exec: fix icount out-of-bounds accessPaolo Bonzini
When icount is active, tb_add_jump is surprisingly called with an out of bounds basic block index. I have no idea how that can work, but it does not seem like a good idea. Clear *last_tb for all TB_EXIT_ICOUNT_EXPIRED cases, even when all you have to do is refill icount_extra. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-01-31trace: switch to modular code generation for sub-directoriesDaniel P. Berrange
Introduce rules in the top level Makefile that are able to generate trace.[ch] files in every subdirectory which has a trace-events file. The top level directory is handled specially, so instead of creating trace.h, it creates trace-root.h. This allows sub-directories to include the top level trace-root.h file, without ambiguity wrt to the trace.g file in the current sub-dir. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170125161417.31949-7-berrange@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-01-27replay: improve interrupt handlingPavel Dovgalyuk
This patch improves interrupt handling in record/replay mode. Now "interrupt" event is saved only when cc->cpu_exec_interrupt returns true. This patch also adds missing return to cpu_exec_interrupt function. Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru> Message-Id: <20170124071708.4572.64023.stgit@PASHA-ISP> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-11-01log: Add locking to large logging blocksRichard Henderson
Reuse the existing locking provided by stdio to keep in_asm, cpu, op, op_opt, op_ind, and out_asm as contiguous blocks. While it isn't possible to interleave e.g. in_asm or op_opt logs because of the TB lock protecting all code generation, it is possible to interleave cpu logs, or to interleave a cpu dump with an out_asm dump. For mingw32, we appear to have no viable solution for this. The locking functions are not properly exported from the system runtime library. Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-10-31Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream-mttcg' into ↵Peter Maydell
staging Base patches for MTTCG enablement. # gpg: Signature made Mon 31 Oct 2016 14:01:41 GMT # gpg: using RSA key 0xBFFBD25F78C7AE83 # gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" # gpg: aka "Paolo Bonzini <pbonzini@redhat.com>" # Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4 E2F7 7E15 100C CD36 69B1 # Subkey fingerprint: F133 3857 4B66 2389 866C 7682 BFFB D25F 78C7 AE83 * remotes/bonzini/tags/for-upstream-mttcg: tcg: move locking for tb_invalidate_phys_page_range up *_run_on_cpu: introduce run_on_cpu_data type cpus: re-factor out handle_icount_deadline tcg: cpus rm tcg_exec_all() tcg: move tcg_exec_all and helpers above thread fn target-arm/arm-powerctl: wake up sleeping CPUs tcg: protect translation related stuff with tb_lock. translate-all: Add assert_(memory|tb)_lock annotations linux-user/elfload: ensure mmap_lock() held while setting up tcg: comment on which functions have to be called with tb_lock held cpu-exec: include cpu_index in CPU_LOG_EXEC messages translate-all: add DEBUG_LOCKING asserts translate_all: DEBUG_FLUSH -> DEBUG_TB_FLUSH cpus: make all_vcpus_paused() return bool Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2016-10-31tcg: protect translation related stuff with tb_lock.KONRAD Frederic
This protects all translation related work with tb_lock() too ensure thread safety. This effectively serialises all code generation. In addition to the code generation we also take the lock for TB invalidation. This has a knock on effect of meaning tb_lock() is held for modification of the SoftMMU TLB by non-self threads which will be used in later patches. Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com> Message-Id: <1439220437-23957-8-git-send-email-fred.konrad@greensocs.com> Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> [AJB: moved into tree, clean-up history] Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Message-Id: <20161027151030.20863-10-alex.bennee@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-10-31cpu-exec: include cpu_index in CPU_LOG_EXEC messagesAlex Bennée
Even more important when debugging MTTCG is seeing which vCPU is currently executing. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Message-Id: <20161027151030.20863-5-alex.bennee@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-10-27Merge remote-tracking branch 'remotes/rth/tags/pull-atomic-20161026' into ↵Peter Maydell
staging cmpxchg emulation of atomics, v8 # gpg: Signature made Wed 26 Oct 2016 16:30:03 BST # gpg: using RSA key 0xAD1270CC4DD0279B # gpg: Good signature from "Richard Henderson <rth7680@gmail.com>" # gpg: aka "Richard Henderson <rth@redhat.com>" # gpg: aka "Richard Henderson <rth@twiddle.net>" # Primary key fingerprint: 9CB1 8DDA F8E8 49AD 2AFC 16A4 AD12 70CC 4DD0 279B * remotes/rth/tags/pull-atomic-20161026: (37 commits) target-alpha: Emulate LL/SC using cmpxchg helpers target-alpha: Introduce MMU_PHYS_IDX target-arm: remove EXCP_STREX + cpu_exclusive_{test, info} linux-user: remove handling of aarch64's EXCP_STREX linux-user: remove handling of ARM's EXCP_STREX target-arm: emulate aarch64's LL/SC using cmpxchg helpers target-arm: emulate SWP with atomic_xchg helper target-arm: emulate LL/SC using cmpxchg helpers target-arm: Rearrange aa32 load and store functions tests: add atomic_add-bench target-i386: remove helper_lock() target-i386: emulate XCHG using atomic helper target-i386: emulate LOCK'ed BTX ops using atomic helpers target-i386: emulate LOCK'ed XADD using atomic helper target-i386: emulate LOCK'ed NEG using cmpxchg helper target-i386: emulate LOCK'ed NOT using atomic helper target-i386: emulate LOCK'ed INC using atomic helper target-i386: emulate LOCK'ed OP instructions using atomic helpers target-i386: emulate LOCK'ed cmpxchg using cmpxchg helpers tcg: Emit barriers with parallel_cpus ... Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2016-10-26tcg: Add EXCP_ATOMICRichard Henderson
When we cannot emulate an atomic operation within a parallel context, this exception allows us to stop the world and try again in a serial context. Reviewed-by: Emilio G. Cota <cota@braap.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-10-25target-m68k: remove m68k_cpu_exec_enter() and m68k_cpu_exec_exit()Laurent Vivier
Update cc_op directly from tcg_gen_insn_start() and restore_state_to_opc() Copied from target-i386 Signed-off-by: Laurent Vivier <laurent@vivier.eu>
2016-10-04cpu: atomically modify cpu->exit_requestAlex Bennée
ThreadSanitizer picks up potential races although we already use barriers to ensure things are in the correct order when processing exit requests. For true C11 defined behaviour across threads we need to use relaxed atomic_set/atomic_read semantics to reassure tsan. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Message-Id: <20160930213106.20186-9-alex.bennee@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-27tcg: Make tb_flush() thread safeSergey Fedorov
Use async_safe_run_on_cpu() to make tb_flush() thread safe. This is possible now that code generation does not happen in the middle of execution. It can happen that multiple threads schedule a safe work to flush the translation buffer. To keep statistics and debugging output sane, always check if the translation buffer has already been flushed. Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> [AJB: minor re-base fixes] Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Message-Id: <1470158864-17651-13-git-send-email-alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-16cpu-exec: Check -dfilter for -d cpuRichard Henderson
Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-09-13tcg: rename tb_find_physical()Sergey Fedorov
In fact, this function does not exactly perform a lookup by physical address as it is descibed for comment on get_page_addr_code(). Thus it may be a bit confusing to have "physical" in it's name. So rename it to tb_htable_lookup() to better reflect its actual functionality. Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Message-Id: <20160715175852.30749-13-sergey.fedorov@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-13tcg: Merge tb_find_slow() and tb_find_fast()Sergey Fedorov
These functions are not too big and can be merged together. This makes locking scheme more clear and easier to follow. Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Message-Id: <20160715175852.30749-12-sergey.fedorov@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-13tcg: Avoid bouncing tb_lock between tb_gen_code() and tb_add_jump()Sergey Fedorov
Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Message-Id: <20160715175852.30749-11-sergey.fedorov@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-13tcg: cpu-exec: remove tb_lock from the hot-pathAlex Bennée
Lock contention in the hot path of moving between existing patched TranslationBlocks is the main drag in multithreaded performance. This patch pushes the tb_lock() usage down to the two places that really need it: - code generation (tb_gen_code) - jump patching (tb_add_jump) The rest of the code doesn't really need to hold a lock as it is either using per-CPU structures, atomically updated or designed to be used in concurrent read situations (qht_lookup). To keep things simple I removed the #ifdef CONFIG_USER_ONLY stuff as the locks become NOPs anyway until the MTTCG work is completed. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Reviewed-by: Sergey Fedorov <sergey.fedorov@linaro.org> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Message-Id: <20160715175852.30749-10-sergey.fedorov@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-13tcg: Prepare TB invalidation for lockless TB lookupPaolo Bonzini
When invalidating a translation block, set an invalid flag into the TranslationBlock structure first. It is also necessary to check whether the target TB is still valid after acquiring 'tb_lock' but before calling tb_add_jump() since TB lookup is to be performed out of 'tb_lock' in future. Note that we don't have to check 'last_tb'; an already invalidated TB will not be executed anyway and it is thus safe to patch it. Suggested-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-13tcg: Prepare safe access to tb_flushed out of tb_lockSergey Fedorov
Ensure atomicity and ordering of CPU's 'tb_flushed' access for future translation block lookup out of 'tb_lock'. This field can only be touched from another thread by tb_flush() in user mode emulation. So the only access to be sequential atomic is: * a single write in tb_flush(); * reads/writes out of 'tb_lock'. In future, before enabling MTTCG in system mode, tb_flush() must be safe and this field becomes unnecessary. Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Message-Id: <20160715175852.30749-5-sergey.fedorov@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-13tcg: Prepare safe tb_jmp_cache lookup out of tb_lockSergey Fedorov
Ensure atomicity of CPU's 'tb_jmp_cache' access for future translation block lookup out of 'tb_lock'. Note that this patch does *not* make CPU's TLB invalidation safe if it is done from some other thread while the CPU is in its execution loop. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Message-Id: <20160715175852.30749-4-sergey.fedorov@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-09-13tcg: Pass last_tb by value to tb_find_fast()Sergey Fedorov
This is a small clean up. tb_find_fast() is a final consumer of this variable so no need to pass it by reference. 'last_tb' is always updated by subsequent cpu_loop_exec_tb() in cpu_exec(). This change also simplifies calling cpu_exec_nocache() in cpu_handle_exception(). Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Message-Id: <20160715175852.30749-3-sergey.fedorov@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-07-17cpu-exec: Move down some declarations in cpu_exec()Sergey Fedorov
This will fix a compiler warning with -Wclobbered: http://lists.nongnu.org/archive/html/qemu-devel/2016-07/msg03347.html Reported-by: Stefan Weil <sw@weilnetz.de> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Message-Id: <20160715193123.28113-1-sergey.fedorov@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-06-11tb hash: track translated blocks with qhtEmilio G. Cota
Having a fixed-size hash table for keeping track of all translation blocks is suboptimal: some workloads are just too big or too small to get maximum performance from the hash table. The MRU promotion policy helps improve performance when the hash table is a little undersized, but it cannot make up for severely undersized hash tables. Furthermore, frequent MRU promotions result in writes that are a scalability bottleneck. For scalability, lookups should only perform reads, not writes. This is not a big deal for now, but it will become one once MTTCG matures. The appended fixes these issues by using qht as the implementation of the TB hash table. This solution is superior to other alternatives considered, namely: - master: implementation in QEMU before this patchset - xxhash: before this patch, i.e. fixed buckets + xxhash hashing + MRU. - xxhash-rcu: fixed buckets + xxhash + RCU list + MRU. MRU is implemented here by adding an intermediate struct that contains the u32 hash and a pointer to the TB; this allows us, on an MRU promotion, to copy said struct (that is not at the head), and put this new copy at the head. After a grace period, the original non-head struct can be eliminated, and after another grace period, freed. - qht-fixed-nomru: fixed buckets + xxhash + qht without auto-resize + no MRU for lookups; MRU for inserts. The appended solution is the following: - qht-dyn-nomru: dynamic number of buckets + xxhash + qht w/ auto-resize + no MRU for lookups; MRU for inserts. The plots below compare the considered solutions. The Y axis shows the boot time (in seconds) of a debian jessie image with arm-softmmu; the X axis sweeps the number of buckets (or initial number of buckets for qht-autoresize). The plots in PNG format (and with errorbars) can be seen here: http://imgur.com/a/Awgnq Each test runs 5 times, and the entire QEMU process is pinned to a single core for repeatability of results. Host: Intel Xeon E5-2690 28 ++------------+-------------+-------------+-------------+------------++ A***** + + + master **A*** + 27 ++ * xxhash ##B###++ | A******A****** xxhash-rcu $$C$$$ | 26 C$$ A******A****** qht-fixed-nomru*%%D%%%++ D%%$$ A******A******A*qht-dyn-mru A*E****A 25 ++ %%$$ qht-dyn-nomru &&F&&&++ B#####% | 24 ++ #C$$$$$ ++ | B### $ | | ## C$$$$$$ | 23 ++ # C$$$$$$ ++ | B###### C$$$$$$ %%%D 22 ++ %B###### C$$$$$$C$$$$$$C$$$$$$C$$$$$$C$$$$$$C | D%%%%%%B###### @E@@@@@@ %%%D%%%@@@E@@@@@@E 21 E@@@@@@E@@@@@@F&&&@@@E@@@&&&D%%%%%%B######B######B######B######B######B + E@@@ F&&& + E@ + F&&& + + 20 ++------------+-------------+-------------+-------------+------------++ 14 16 18 20 22 24 log2 number of buckets Host: Intel i7-4790K 14.5 ++------------+------------+-------------+------------+------------++ A** + + + master **A*** + 14 ++ ** xxhash ##B###++ 13.5 ++ ** xxhash-rcu $$C$$$++ | qht-fixed-nomru %%D%%% | 13 ++ A****** qht-dyn-mru @@E@@@++ | A*****A******A****** qht-dyn-nomru &&F&&& | 12.5 C$$ A******A******A*****A****** ***A 12 ++ $$ A*** ++ D%%% $$ | 11.5 ++ %% ++ B### %C$$$$$$ | 11 ++ ## D%%%%% C$$$$$ ++ | # % C$$$$$$ | 10.5 F&&&&&&B######D%%%%% C$$$$$$C$$$$$$C$$$$$$C$$$$$C$$$$$$ $$$C 10 E@@@@@@E@@@@@@B#####B######B######E@@@@@@E@@@%%%D%%%%%D%%%###B######B + F&& D%%%%%%B######B######B#####B###@@@D%%% + 9.5 ++------------+------------+-------------+------------+------------++ 14 16 18 20 22 24 log2 number of buckets Note that the original point before this patch series is X=15 for "master"; the little sensitivity to the increased number of buckets is due to the poor hashing function in master. xxhash-rcu has significant overhead due to the constant churn of allocating and deallocating intermediate structs for implementing MRU. An alternative would be do consider failed lookups as "maybe not there", and then acquire the external lock (tb_lock in this case) to really confirm that there was indeed a failed lookup. This, however, would not be enough to implement dynamic resizing--this is more complex: see "Resizable, Scalable, Concurrent Hash Tables via Relativistic Programming" by Triplett, McKenney and Walpole. This solution was discarded due to the very coarse RCU read critical sections that we have in MTTCG; resizing requires waiting for readers after every pointer update, and resizes require many pointer updates, so this would quickly become prohibitive. qht-fixed-nomru shows that MRU promotion is advisable for undersized hash tables. However, qht-dyn-mru shows that MRU promotion is not important if the hash table is properly sized: there is virtually no difference in performance between qht-dyn-nomru and qht-dyn-mru. Before this patch, we're at X=15 on "xxhash"; after this patch, we're at X=15 @ qht-dyn-nomru. This patch thus matches the best performance that we can achieve with optimum sizing of the hash table, while keeping the hash table scalable for readers. The improvement we get before and after this patch for booting debian jessie with arm-softmmu is: - Intel Xeon E5-2690: 10.5% less time - Intel i7-4790K: 5.2% less time We could get this same improvement _for this particular workload_ by statically increasing the size of the hash table. But this would hurt workloads that do not need a large hash table. The dynamic (upward) resizing allows us to start small and enlarge the hash table as needed. A quick note on downsizing: the table is resized back to 2**15 buckets on every tb_flush; this makes sense because it is not guaranteed that the table will reach the same number of TBs later on (e.g. most bootup code is thrown away after boot); it makes sense to grow the hash table as more code blocks are translated. This also avoids the complication of having to build downsizing hysteresis logic into qht. Reviewed-by: Sergey Fedorov <serge.fedorov@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Emilio G. Cota <cota@braap.org> Message-Id: <1465412133-3029-15-git-send-email-cota@braap.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-06-11tb hash: hash phys_pc, pc, and flags with xxhashEmilio G. Cota
For some workloads such as arm bootup, tb_phys_hash is performance-critical. The is due to the high frequency of accesses to the hash table, originated by (frequent) TLB flushes that wipe out the cpu-private tb_jmp_cache's. More info: https://lists.nongnu.org/archive/html/qemu-devel/2016-03/msg05098.html To dig further into this I modified an arm image booting debian jessie to immediately shut down after boot. Analysis revealed that quite a bit of time is unnecessarily spent in tb_phys_hash: the cause is poor hashing that results in very uneven loading of chains in the hash table's buckets; the longest observed chain had ~550 elements. The appended addresses this with two changes: 1) Use xxhash as the hash table's hash function. xxhash is a fast, high-quality hashing function. 2) Feed the hashing function with not just tb_phys, but also pc and flags. This improves performance over using just tb_phys for hashing, since that resulted in some hash buckets having many TB's, while others getting very few; with these changes, the longest observed chain on a single hash bucket is brought down from ~550 to ~40. Tests show that the other element checked for in tb_find_physical, cs_base, is always a match when tb_phys+pc+flags are a match, so hashing cs_base is wasteful. It could be that this is an ARM-only thing, though. UPDATE: On Tue, Apr 05, 2016 at 08:41:43 -0700, Richard Henderson wrote: > The cs_base field is only used by i386 (in 16-bit modes), and sparc (for a TB > consisting of only a delay slot). > It may well still turn out to be reasonable to ignore cs_base for hashing. BTW, after this change the hash table should not be called "tb_hash_phys" anymore; this is addressed later in this series. This change gives consistent bootup time improvements. I tested two host machines: - Intel Xeon E5-2690: 11.6% less time - Intel i7-4790K: 19.2% less time Increasing the number of hash buckets yields further improvements. However, using a larger, fixed number of buckets can degrade performance for other workloads that do not translate as many blocks (600K+ for debian-jessie arm bootup). This is dealt with later in this series. Reviewed-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Emilio G. Cota <cota@braap.org> Message-Id: <1465412133-3029-8-git-send-email-cota@braap.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-05-26cpu-exec: Fix direct jump to TB spanning pageSergey Fedorov
It is not safe to make a direct jump to a TB spanning two pages in system emulation because the mapping for the second page can get changed but we don't take care of direct jumps in this case. However in user mode emulation, this is not the case because there's only static address translation and TBs are always invalidated properly. Fixes: 5b053a4a2827 ("tcg: Clean up direct block chaining safety checks") Reported-by: Max Filippov <jcmvbkbc@gmail.com> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Tested-by: Max Filippov <jcmvbkbc@gmail.com> Message-id: 1463404380-29302-1-git-send-email-sergey.fedorov@linaro.org Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2016-05-19cpu: move exec-all.h inclusion out of cpu.hPaolo Bonzini
exec-all.h contains TCG-specific definitions. It is not needed outside TCG-specific files such as translate.c, exec.c or *helper.c. One generic function had snuck into include/exec/exec-all.h; move it to include/qom/cpu.h. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-05-12cpu-exec: Clean up 'interrupt_request' reloading in cpu_handle_interrupt()Sergey Fedorov
Suggested-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Message-Id: <1463071937-26607-1-git-send-email-sergey.fedorov@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-05-12cpu-exec: Remove unused 'x86_cpu' and 'env' from cpu_exec()Sergey Fedorov
Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Message-Id: <1462962111-32237-6-git-send-email-sergey.fedorov@linaro.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-05-12cpu-exec: Move TB execution stuff out of cpu_exec()Sergey Fedorov
Simplify cpu_exec() by extracting TB execution code outside of cpu_exec() into a new static inline function cpu_loop_exec_tb(). Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Message-Id: <1462962111-32237-5-git-send-email-sergey.fedorov@linaro.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-05-12cpu-exec: Move interrupt handling out of cpu_exec()Sergey Fedorov
Simplify cpu_exec() by extracting interrupt handling code outside of cpu_exec() into a new static inline function cpu_handle_interrupt(). Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Message-Id: <1462962111-32237-4-git-send-email-sergey.fedorov@linaro.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-05-12cpu-exec: Move exception handling out of cpu_exec()Sergey Fedorov
Simplify cpu_exec() by extracting exception handling code out of cpu_exec() into a new static inline function cpu_handle_exception(). Also make cpu_handle_debug_exception() inline as it is used only once. Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Message-Id: <1462962111-32237-3-git-send-email-sergey.fedorov@linaro.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-05-12cpu-exec: Move halt handling out of cpu_exec()Sergey Fedorov
Simplify cpu_exec() by extracting CPU halt state handling code out of cpu_exec() into a new static inline function cpu_handle_halt(). Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net> Message-Id: <1462962111-32237-2-git-send-email-sergey.fedorov@linaro.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-05-12cpu-exec: Remove relic orphaned commentSergey Fedorov
This comment should have been deleted by commit 0ac087f1f3ae ("removed unused code") but somehow it is still here. There's no point to keep it. Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Message-Id: <1462286050-21778-1-git-send-email-sergey.fedorov@linaro.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
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