Jonathan Cameron <jonathan.came...@huawei.com> writes: > On Thu, 01 Feb 2024 16:45:30 +0000 > Alex Bennée <alex.ben...@linaro.org> wrote: > >> Jonathan Cameron <jonathan.came...@huawei.com> writes: >> >> > On Thu, 1 Feb 2024 16:00:56 +0000 >> > Peter Maydell <peter.mayd...@linaro.org> wrote: >> > >> >> On Thu, 1 Feb 2024 at 15:17, Alex Bennée <alex.ben...@linaro.org> wrote: >> >> > >> >> > Peter Maydell <peter.mayd...@linaro.org> writes: >> >> > > So, that looks like: >> >> > > * we call cpu_tb_exec(), which executes some generated code >> >> > > * that generated code calls the lookup_tb_ptr helper to see >> >> > > if we have a generated TB already for the address we're going >> >> > > to execute next >> >> > > * lookup_tb_ptr probes the TLB to see if we know the host RAM >> >> > > address for the guest address >> >> > > * this results in a TLB walk for an instruction fetch >> >> > > * the page table descriptor load is to IO memory >> >> > > * io_prepare assumes it needs to do a TLB recompile, because >> >> > > can_do_io is clear >> >> > > >> >> > > I am not surprised that the corner case of "the guest put its >> >> > > page tables in an MMIO device" has not yet come up :-) >> >> > > >> >> > > I'm really not sure how the icount handling should interact >> >> > > with that... >> >> > >> >> > Its not just icount - we need to handle it for all modes now. That said >> >> > seeing as we are at the end of a block shouldn't can_do_io be set? >> >> >> >> The lookup_tb_ptr helper gets called from tcg_gen_goto_tb(), >> >> which happens earlier than the tb_stop callback (it can >> >> happen in the trans function for branch etc insns, for >> >> example). >> >> >> >> I think it should be OK to clear can_do_io at the start >> >> of the lookup_tb_ptr helper, something like: >> >> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c >> >> index 977576ca143..7818537f318 100644 >> >> --- a/accel/tcg/cpu-exec.c >> >> +++ b/accel/tcg/cpu-exec.c >> >> @@ -396,6 +396,15 @@ const void *HELPER(lookup_tb_ptr)(CPUArchState *env) >> >> uint64_t cs_base; >> >> uint32_t flags, cflags; >> >> >> >> + /* >> >> + * By definition we've just finished a TB, so I/O is OK. >> >> + * Avoid the possibility of calling cpu_io_recompile() if >> >> + * a page table walk triggered by tb_lookup() calling >> >> + * probe_access_internal() happens to touch an MMIO device. >> >> + * The next TB, if we chain to it, will clear the flag again. >> >> + */ >> >> + cpu->neg.can_do_io = true; >> >> + >> >> cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags); >> >> >> >> cflags = curr_cflags(cpu); >> >> >> >> -- PMM >> > >> > No joy. Seems like a very similar backtrace. >> > >> > Thread 5 "qemu-system-x86" received signal SIGABRT, Aborted. >> > [Switching to Thread 0x7ffff4efe6c0 (LWP 23937)] >> > __pthread_kill_implementation (no_tid=0, signo=6, threadid=<optimized >> > out>) at ./nptl/pthread_kill.c:44 >> > 44 ./nptl/pthread_kill.c: No such file or directory. >> > (gdb) bt >> > #0 __pthread_kill_implementation (no_tid=0, signo=6, threadid=<optimized >> > out>) at ./nptl/pthread_kill.c:44 >> > #1 __pthread_kill_internal (signo=6, threadid=<optimized out>) at >> > ./nptl/pthread_kill.c:78 >> > #2 __GI___pthread_kill (threadid=<optimized out>, signo=signo@entry=6) at >> > ./nptl/pthread_kill.c:89 >> > #3 0x00007ffff77c43b6 in __GI_raise (sig=sig@entry=6) at >> > ../sysdeps/posix/raise.c:26 >> > #4 0x00007ffff77aa87c in __GI_abort () at ./stdlib/abort.c:79 >> > #5 0x0000555555c4d19e in cpu_abort (cpu=cpu@entry=0x5555578e0cb0, >> > fmt=fmt@entry=0x555556048ee8 "cpu_io_recompile: could not find TB for >> > pc=%p") at ../../cpu-target.c:373 >> > #6 0x0000555555c9cb25 in cpu_io_recompile (cpu=cpu@entry=0x5555578e0cb0, >> > retaddr=retaddr@entry=0) at ../../accel/tcg/translate-all.c:611 >> > #7 0x0000555555c9f744 in io_prepare (retaddr=0, addr=19595790664, >> > attrs=..., xlat=<optimized out>, cpu=0x5555578e0cb0, out_offset=<synthetic >> > pointer>) at ../../accel/tcg/cputlb.c:1339 >> > #8 do_ld_mmio_beN (cpu=0x5555578e0cb0, full=0x7ffe88012890, >> > ret_be=ret_be@entry=0, addr=19595790664, size=size@entry=8, mmu_idx=4, >> > type=MMU_DATA_LOAD, ra=0) at ../../accel/tcg/cputlb.c:2030 >> > #9 0x0000555555ca0ecd in do_ld_8 (cpu=cpu@entry=0x5555578e0cb0, >> > p=p@entry=0x7ffff4efcdd0, mmu_idx=<optimized out>, >> > type=type@entry=MMU_DATA_LOAD, memop=<optimized out>, ra=ra@entry=0) at >> > ../../accel/tcg/cputlb.c:2356 >> > #10 0x0000555555ca332f in do_ld8_mmu (cpu=cpu@entry=0x5555578e0cb0, >> > addr=addr@entry=19595790664, oi=oi@entry=52, ra=ra@entry=0, >> > access_type=access_type@entry=MMU_DATA_LOAD) at >> > ../../accel/tcg/cputlb.c:2439 >> > #11 0x0000555555ca5e69 in cpu_ldq_mmu (ra=0, oi=52, addr=19595790664, >> > env=0x5555578e3470) at ../../accel/tcg/ldst_common.c.inc:169 >> > #12 cpu_ldq_le_mmuidx_ra (env=0x5555578e3470, addr=19595790664, >> > mmu_idx=<optimized out>, ra=ra@entry=0) at >> > ../../accel/tcg/ldst_common.c.inc:301 >> > #13 0x0000555555b4b5de in ptw_ldq (in=0x7ffff4efcf10) at >> > ../../target/i386/tcg/sysemu/excp_helper.c:98 >> > #14 ptw_ldq (in=0x7ffff4efcf10) at >> > ../../target/i386/tcg/sysemu/excp_helper.c:93 >> > #15 mmu_translate (env=env@entry=0x5555578e3470, in=0x7ffff4efcfd0, >> > out=0x7ffff4efcfa0, err=err@entry=0x7ffff4efcfb0) at >> > ../../target/i386/tcg/sysemu/excp_helper.c:173 >> > #16 0x0000555555b4c3f3 in get_physical_address (err=0x7ffff4efcfb0, >> > out=0x7ffff4efcfa0, mmu_idx=0, access_type=MMU_DATA_STORE, >> > addr=18386491786698339392, env=0x5555578e3470) at >> > ../../target/i386/tcg/sysemu/excp_helper.c:578 >> > #17 x86_cpu_tlb_fill (cs=0x5555578e0cb0, addr=18386491786698339392, >> > size=<optimized out>, access_type=MMU_DATA_STORE, mmu_idx=0, >> > probe=<optimized out>, retaddr=140736029817822) at >> > ../../target/i386/tcg/sysemu/excp_helper.c:604 >> > #18 0x0000555555ca0df9 in tlb_fill (retaddr=140736029817822, mmu_idx=0, >> > access_type=MMU_DATA_STORE, size=<optimized out>, >> > addr=18386491786698339392, cpu=0x7ffff4efd120) at >> > ../../accel/tcg/cputlb.c:1315 >> > #19 mmu_lookup1 (cpu=cpu@entry=0x5555578e0cb0, >> > data=data@entry=0x7ffff4efd120, mmu_idx=0, >> > access_type=access_type@entry=MMU_DATA_STORE, ra=ra@entry=140736029817822) >> > at ../../accel/tcg/cputlb.c:1713 >> > #20 0x0000555555ca2b71 in mmu_lookup (cpu=0x5555578e0cb0, >> > addr=18386491786698339392, oi=<optimized out>, ra=140736029817822, >> > type=MMU_DATA_STORE, l=0x7ffff4efd120) at ../../accel/tcg/cputlb.c:1803 >> > #21 0x0000555555ca3e5d in do_st8_mmu (cpu=0x5555578e0cb0, addr=23937, >> > val=18386491784638059520, oi=6, ra=140736029817822) at >> > ../../accel/tcg/cputlb.c:2853 >> > #22 0x00007fffa9107c63 in code_gen_buffer () >> >> No thats different - we are actually writing to the MMIO region here. >> But the fact we hit cpu_abort because we can't find the TB we are >> executing is a little problematic. >> >> Does ra properly point to the code buffer here? > > Err. How would I tell?
(gdb) p/x 140736029817822 $1 = 0x7fffa9107bde seems off because code_gen_buffer starts at 0x00007fffa9107c63 > > I'll confess I have almost no idea what is going on in TCG :( > > Can learn but it won't be quick. > > J > >> >> > #23 0x0000555555c9395b in cpu_tb_exec (cpu=cpu@entry=0x5555578e0cb0, >> > itb=itb@entry=0x7fffa9107980 <code_gen_buffer+17856851>, >> > tb_exit=tb_exit@entry=0x7ffff4efd718) at ../../accel/tcg/cpu-exec.c:442 At this point I'd run under rr and set a bp at cpu_tb_exec, reverse-continue and then see how we ended up off-piste with a retaddr that can't be resolved. >> > #24 0x0000555555c93ec0 in cpu_loop_exec_tb (tb_exit=0x7ffff4efd718, >> > last_tb=<synthetic pointer>, pc=<optimized out>, tb=0x7fffa9107980 >> > <code_gen_buffer+17856851>, cpu=0x5555578e0cb0) at >> > ../../accel/tcg/cpu-exec.c:897 >> > #25 cpu_exec_loop (cpu=cpu@entry=0x5555578e0cb0, >> > sc=sc@entry=0x7ffff4efd7b0) at ../../accel/tcg/cpu-exec.c:1012 >> > #26 0x0000555555c946d1 in cpu_exec_setjmp (cpu=cpu@entry=0x5555578e0cb0, >> > sc=sc@entry=0x7ffff4efd7b0) at ../../accel/tcg/cpu-exec.c:1029 >> > #27 0x0000555555c94ebc in cpu_exec (cpu=cpu@entry=0x5555578e0cb0) at >> > ../../accel/tcg/cpu-exec.c:1055 >> > #28 0x0000555555cb8f53 in tcg_cpu_exec (cpu=cpu@entry=0x5555578e0cb0) at >> > ../../accel/tcg/tcg-accel-ops.c:76 >> > #29 0x0000555555cb90b0 in mttcg_cpu_thread_fn >> > (arg=arg@entry=0x5555578e0cb0) at ../../accel/tcg/tcg-accel-ops-mttcg.c:95 >> > #30 0x0000555555e57180 in qemu_thread_start (args=0x555557956000) at >> > ../../util/qemu-thread-posix.c:541 >> > #31 0x00007ffff78176ba in start_thread (arg=<optimized out>) at >> > ./nptl/pthread_create.c:444 >> > #32 0x00007ffff78a60d0 in clone3 () at >> > ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81 >> -- Alex Bennée Virtualisation Tech Lead @ Linaro
