From 228168cbb7cc40bfb1621b0b6868c018b522276a Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Fri, 11 Jun 2021 23:08:28 -0700 Subject: linux-user: Set CF_PARALLEL when mapping shared memory MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signal the translator to use host atomic instructions for guest operations, insofar as it is possible. This is the best we can do to allow the guest to interact atomically with other processes. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/121 Signed-off-by: Richard Henderson Reviewed-by: Alex Bennée Message-Id: <20210612060828.695332-1-richard.henderson@linaro.org> Signed-off-by: Laurent Vivier --- linux-user/mmap.c | 14 ++++++++++++++ linux-user/syscall.c | 12 ++++++++++++ 2 files changed, 26 insertions(+) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 7e3b245..0e10385 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -451,6 +451,20 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot, goto fail; } + /* + * If we're mapping shared memory, ensure we generate code for parallel + * execution and flush old translations. This will work up to the level + * supported by the host -- anything that requires EXCP_ATOMIC will not + * be atomic with respect to an external process. + */ + if (flags & MAP_SHARED) { + CPUState *cpu = thread_cpu; + if (!(cpu->tcg_cflags & CF_PARALLEL)) { + cpu->tcg_cflags |= CF_PARALLEL; + tb_flush(cpu); + } + } + real_start = start & qemu_host_page_mask; host_offset = offset & qemu_host_page_mask; diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 974dd46..54037db 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -4603,6 +4603,7 @@ static inline abi_ulong target_shmlba(CPUArchState *cpu_env) static inline abi_ulong do_shmat(CPUArchState *cpu_env, int shmid, abi_ulong shmaddr, int shmflg) { + CPUState *cpu = env_cpu(cpu_env); abi_long raddr; void *host_raddr; struct shmid_ds shm_info; @@ -4633,6 +4634,17 @@ static inline abi_ulong do_shmat(CPUArchState *cpu_env, mmap_lock(); + /* + * We're mapping shared memory, so ensure we generate code for parallel + * execution and flush old translations. This will work up to the level + * supported by the host -- anything that requires EXCP_ATOMIC will not + * be atomic with respect to an external process. + */ + if (!(cpu->tcg_cflags & CF_PARALLEL)) { + cpu->tcg_cflags |= CF_PARALLEL; + tb_flush(cpu); + } + if (shmaddr) host_raddr = shmat(shmid, (void *)g2h_untagged(shmaddr), shmflg); else { -- cgit v1.1