diff options
author | Richard Henderson <richard.henderson@linaro.org> | 2019-07-09 10:33:36 +0200 |
---|---|---|
committer | Richard Henderson <richard.henderson@linaro.org> | 2019-07-14 12:19:01 +0200 |
commit | 52ba13f042714c4086416973fb88e2465e0888a1 (patch) | |
tree | d7504bd7a0d6b1ca6f741897e39ee3eed34a68c1 /accel/tcg | |
parent | 2fbb2353ce8d098e172cd25024fc221c1c8e3591 (diff) |
tcg: Release mmap_lock on translation fault
Turn helper_retaddr into a multi-state flag that may now also
indicate when we're performing a read on behalf of the translator.
In this case, release the mmap_lock before the longjmp back to
the main cpu loop, and thereby avoid a failing assert therein.
Fixes: https://bugs.launchpad.net/qemu/+bug/1832353
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Diffstat (limited to 'accel/tcg')
-rw-r--r-- | accel/tcg/user-exec.c | 66 |
1 files changed, 47 insertions, 19 deletions
diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c index 4384b59a4d..897d1571c4 100644 --- a/accel/tcg/user-exec.c +++ b/accel/tcg/user-exec.c @@ -64,27 +64,56 @@ static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info, CPUState *cpu = current_cpu; CPUClass *cc; unsigned long address = (unsigned long)info->si_addr; - MMUAccessType access_type; + MMUAccessType access_type = is_write ? MMU_DATA_STORE : MMU_DATA_LOAD; - /* We must handle PC addresses from two different sources: - * a call return address and a signal frame address. - * - * Within cpu_restore_state_from_tb we assume the former and adjust - * the address by -GETPC_ADJ so that the address is within the call - * insn so that addr does not accidentally match the beginning of the - * next guest insn. - * - * However, when the PC comes from the signal frame, it points to - * the actual faulting host insn and not a call insn. Subtracting - * GETPC_ADJ in that case may accidentally match the previous guest insn. - * - * So for the later case, adjust forward to compensate for what - * will be done later by cpu_restore_state_from_tb. - */ - if (helper_retaddr) { + switch (helper_retaddr) { + default: + /* + * Fault during host memory operation within a helper function. + * The helper's host return address, saved here, gives us a + * pointer into the generated code that will unwind to the + * correct guest pc. + */ pc = helper_retaddr; - } else { + break; + + case 0: + /* + * Fault during host memory operation within generated code. + * (Or, a unrelated bug within qemu, but we can't tell from here). + * + * We take the host pc from the signal frame. However, we cannot + * use that value directly. Within cpu_restore_state_from_tb, we + * assume PC comes from GETPC(), as used by the helper functions, + * so we adjust the address by -GETPC_ADJ to form an address that + * is within the call insn, so that the address does not accidentially + * match the beginning of the next guest insn. However, when the + * pc comes from the signal frame it points to the actual faulting + * host memory insn and not the return from a call insn. + * + * Therefore, adjust to compensate for what will be done later + * by cpu_restore_state_from_tb. + */ pc += GETPC_ADJ; + break; + + case 1: + /* + * Fault during host read for translation, or loosely, "execution". + * + * The guest pc is already pointing to the start of the TB for which + * code is being generated. If the guest translator manages the + * page crossings correctly, this is exactly the correct address + * (and if the translator doesn't handle page boundaries correctly + * there's little we can do about that here). Therefore, do not + * trigger the unwinder. + * + * Like tb_gen_code, release the memory lock before cpu_loop_exit. + */ + pc = 0; + access_type = MMU_INST_FETCH; + mmap_unlock(); + break; } /* For synchronous signals we expect to be coming from the vCPU @@ -155,7 +184,6 @@ static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info, clear_helper_retaddr(); cc = CPU_GET_CLASS(cpu); - access_type = is_write ? MMU_DATA_STORE : MMU_DATA_LOAD; cc->tlb_fill(cpu, address, 0, access_type, MMU_USER_IDX, false, pc); g_assert_not_reached(); } |