From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=58305 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PcNP0-0007XR-7a for qemu-devel@nongnu.org; Mon, 10 Jan 2011 14:27:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PcNOx-0002X9-AD for qemu-devel@nongnu.org; Mon, 10 Jan 2011 14:27:36 -0500 Received: from mail-ey0-f173.google.com ([209.85.215.173]:52690) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PcNOw-0002X1-W6 for qemu-devel@nongnu.org; Mon, 10 Jan 2011 14:27:35 -0500 Received: by eyg7 with SMTP id 7so6124982eyg.4 for ; Mon, 10 Jan 2011 11:27:34 -0800 (PST) Date: Mon, 10 Jan 2011 20:27:30 +0100 From: "Edgar E. Iglesias" Message-ID: <20110110192730.GA11412@laped.lan> References: <1294680882-31930-1-git-send-email-aurelien@aurel32.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1294680882-31930-1-git-send-email-aurelien@aurel32.net> Subject: [Qemu-devel] Re: [PATCH] tcg arm/mips/ia64: add a comment about retranslation and caches List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Aurelien Jarno Cc: qemu-devel@nongnu.org, Alexander Graf On Mon, Jan 10, 2011 at 06:34:42PM +0100, Aurelien Jarno wrote: > Add a comment about cache coherency and retranslation, so that people > developping new targets based on existing ones are warned of the issue. > > Cc: Alexander Graf > Cc: Edgar E. Iglesias > Signed-off-by: Aurelien Jarno Looks good to me, thanks. Acked-by: Edgar E. Iglesias > --- > tcg/arm/tcg-target.c | 3 +++ > tcg/ia64/tcg-target.c | 3 +++ > tcg/mips/tcg-target.c | 4 +++- > 3 files changed, 9 insertions(+), 1 deletions(-) > > diff --git a/tcg/arm/tcg-target.c b/tcg/arm/tcg-target.c > index 1eb5605..918e2f7 100644 > --- a/tcg/arm/tcg-target.c > +++ b/tcg/arm/tcg-target.c > @@ -352,6 +352,9 @@ static inline void tcg_out_b(TCGContext *s, int cond, int32_t offset) > > static inline void tcg_out_b_noaddr(TCGContext *s, int cond) > { > + /* We pay attention here to not modify the branch target by skipping > + the corresponding bytes. This ensure that caches and memory are > + kept coherent during retranslation. */ > #ifdef HOST_WORDS_BIGENDIAN > tcg_out8(s, (cond << 4) | 0x0a); > s->code_ptr += 3; > diff --git a/tcg/ia64/tcg-target.c b/tcg/ia64/tcg-target.c > index e2e44f7..8dac7f7 100644 > --- a/tcg/ia64/tcg-target.c > +++ b/tcg/ia64/tcg-target.c > @@ -871,6 +871,9 @@ static void tcg_out_br(TCGContext *s, int label_index) > { > TCGLabel *l = &s->labels[label_index]; > > + /* We pay attention here to not modify the branch target by reading > + the existing value and using it again. This ensure that caches and > + memory are kept coherent during retranslation. */ > tcg_out_bundle(s, mmB, > tcg_opc_m48(TCG_REG_P0, OPC_NOP_M48, 0), > tcg_opc_m48(TCG_REG_P0, OPC_NOP_M48, 0), > diff --git a/tcg/mips/tcg-target.c b/tcg/mips/tcg-target.c > index 4e92a50..e04b0dc 100644 > --- a/tcg/mips/tcg-target.c > +++ b/tcg/mips/tcg-target.c > @@ -351,7 +351,9 @@ static inline void tcg_out_opc_imm(TCGContext *s, int opc, int rt, int rs, int i > */ > static inline void tcg_out_opc_br(TCGContext *s, int opc, int rt, int rs) > { > - /* We need to keep the offset unchanged for retranslation */ > + /* We pay attention here to not modify the branch target by reading > + the existing value and using it again. This ensure that caches and > + memory are kept coherent during retranslation. */ > uint16_t offset = (uint16_t)(*(uint32_t *) s->code_ptr); > > tcg_out_opc_imm(s, opc, rt, rs, offset); > -- > 1.7.2.3 >