From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56503) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bJ8d8-0008Vj-44 for qemu-devel@nongnu.org; Fri, 01 Jul 2016 20:17:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bJ8d3-0000RT-Ta for qemu-devel@nongnu.org; Fri, 01 Jul 2016 20:17:53 -0400 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:58839) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bJ8d1-0000Qd-K1 for qemu-devel@nongnu.org; Fri, 01 Jul 2016 20:17:49 -0400 Date: Fri, 1 Jul 2016 20:17:36 -0400 From: "Emilio G. Cota" Message-ID: <20160702001736.GA2295@flamenco> References: <1467389770-9738-1-git-send-email-alex.bennee@linaro.org> <1467389770-9738-2-git-send-email-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1467389770-9738-2-git-send-email-alex.bennee@linaro.org> Subject: Re: [Qemu-devel] [PATCH 1/2] tcg: Ensure safe tb_jmp_cache lookup out of 'tb_lock' List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex =?iso-8859-1?Q?Benn=E9e?= Cc: mttcg@listserver.greensocs.com, qemu-devel@nongnu.org, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, serge.fdrv@gmail.com, bobby.prani@gmail.com, rth@twiddle.net, mark.burton@greensocs.com, pbonzini@redhat.com, jan.kiszka@siemens.com, peter.maydell@linaro.org, claudio.fontana@huawei.com, Sergey Fedorov , Peter Crosthwaite On Fri, Jul 01, 2016 at 17:16:09 +0100, Alex Bennée wrote: > From: Sergey Fedorov (snip) > @@ -333,7 +338,7 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu, > is executed. */ > cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags); > tb_lock(); > - tb = cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)]; > + tb = atomic_read(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)]); > if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base || > tb->flags != flags)) { > tb = tb_find_slow(cpu, pc, cs_base, flags); > diff --git a/translate-all.c b/translate-all.c > index eaa95e4..1fcfe79 100644 > --- a/translate-all.c > +++ b/translate-all.c > @@ -1004,11 +1004,16 @@ void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr) > invalidate_page_bitmap(p); > } > > + /* Ensure that we won't find the TB in the shared hash table > + * if we con't see it in CPU's local cache. s/con't/can't/ > + * Pairs with smp_rmb() in tb_find_slow(). */ > + smp_wmb(); This fence is already embedded in qht_remove, since it internally calls seqlock_write_end() on a successful removal, so we could get away with a comment instead of emitting a redundant fence. However, if qht ever changed its implementation this would have to be taken into account. So I'd be OK with emitting the fence here too. > + > /* remove the TB from the hash list */ > h = tb_jmp_cache_hash_func(tb->pc); > CPU_FOREACH(cpu) { > if (cpu->tb_jmp_cache[h] == tb) { Missing atomic_read here: if (atomic_read(cpu->tb_jmp_cache[...])) { > - cpu->tb_jmp_cache[h] = NULL; > + atomic_set(&cpu->tb_jmp_cache[h], NULL); Other than that, Reviewed-by: Emilio G. Cota