From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49948) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fTp1f-0001Oi-E6 for qemu-devel@nongnu.org; Fri, 15 Jun 2018 09:44:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fTp1b-0007JX-8O for qemu-devel@nongnu.org; Fri, 15 Jun 2018 09:44:27 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:53256 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fTp1b-0007JP-0r for qemu-devel@nongnu.org; Fri, 15 Jun 2018 09:44:23 -0400 Date: Fri, 15 Jun 2018 16:44:21 +0300 From: "Michael S. Tsirkin" Message-ID: <20180615164312-mutt-send-email-mst@kernel.org> References: <20180615062547.4798-1-richard.henderson@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180615062547.4798-1-richard.henderson@linaro.org> Subject: Re: [Qemu-devel] [PATCH] tcg: Reduce max TB opcode count List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson Cc: qemu-devel@nongnu.org, Jason@zx2c4.com, pmatouse@redhat.com, mdroth@linux.vnet.ibm.com, pjp@redhat.com, sstabellini@kernel.org, pbonzini@redhat.com, crosthwaite.peter@gmail.com, sw@weilnetz.de On Thu, Jun 14, 2018 at 08:25:47PM -1000, Richard Henderson wrote: > Also, assert that we don't overflow any of two different offsets into > the TB. Both unwind and goto_tb both record a uint16_t for later use. > > Signed-off-by: Richard Henderson > --- > > This fixes an arm-softmmu test case forwarded to me by Michael Tsirkin. > > There is a TB generated from that test case that runs to 7800 opcodes, > and compiles to 96k on an x64 host. This overflows the 16-bit offset > in which we record the goto_tb reset offset. Because of that overflow, > we install a jump destination that goes to neverland. Boom. > > With this reduced op count, the same TB compiles to about 48k for > both x64 and ppc64le hosts, and neither assertion fires. > > > r~ I just forwarded it: Reported-by: "Jason A. Donenfeld" > > --- > tcg/tcg.h | 2 +- > tcg/aarch64/tcg-target.inc.c | 2 +- > tcg/arm/tcg-target.inc.c | 2 +- > tcg/i386/tcg-target.inc.c | 2 +- > tcg/mips/tcg-target.inc.c | 2 +- > tcg/ppc/tcg-target.inc.c | 4 ++-- > tcg/s390/tcg-target.inc.c | 2 +- > tcg/sparc/tcg-target.inc.c | 4 ++-- > tcg/tcg.c | 13 ++++++++++++- > tcg/tci/tcg-target.inc.c | 2 +- > 10 files changed, 23 insertions(+), 12 deletions(-) > > diff --git a/tcg/tcg.h b/tcg/tcg.h > index 532d2a0710..2902a51505 100644 > --- a/tcg/tcg.h > +++ b/tcg/tcg.h > @@ -852,7 +852,7 @@ static inline bool tcg_op_buf_full(void) > * such that a RISC host can reasonably use a 16-bit signed > * branch within the TB. > */ > - return tcg_ctx->nb_ops >= 8000; > + return tcg_ctx->nb_ops >= 4000; > } > > /* pool based memory allocation */ > diff --git a/tcg/aarch64/tcg-target.inc.c b/tcg/aarch64/tcg-target.inc.c > index be3192078d..4562d36d1b 100644 > --- a/tcg/aarch64/tcg-target.inc.c > +++ b/tcg/aarch64/tcg-target.inc.c > @@ -1733,7 +1733,7 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, > tcg_out_insn(s, 3305, LDR, offset, TCG_REG_TMP); > } > tcg_out_insn(s, 3207, BR, TCG_REG_TMP); > - s->tb_jmp_reset_offset[a0] = tcg_current_code_size(s); > + set_jmp_reset_offset(s, a0); > break; > > case INDEX_op_goto_ptr: > diff --git a/tcg/arm/tcg-target.inc.c b/tcg/arm/tcg-target.inc.c > index 56a32a470f..e1fbf465cb 100644 > --- a/tcg/arm/tcg-target.inc.c > +++ b/tcg/arm/tcg-target.inc.c > @@ -1822,7 +1822,7 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc, > tcg_out_movi32(s, COND_AL, base, ptr - dil); > } > tcg_out_ld32_12(s, COND_AL, TCG_REG_PC, base, dil); > - s->tb_jmp_reset_offset[args[0]] = tcg_current_code_size(s); > + set_jmp_reset_offset(s, args[0]); > } > break; > case INDEX_op_goto_ptr: > diff --git a/tcg/i386/tcg-target.inc.c b/tcg/i386/tcg-target.inc.c > index 0d0ff524b7..e87b0d445e 100644 > --- a/tcg/i386/tcg-target.inc.c > +++ b/tcg/i386/tcg-target.inc.c > @@ -2245,7 +2245,7 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc, > tcg_out_modrm_offset(s, OPC_GRP5, EXT5_JMPN_Ev, -1, > (intptr_t)(s->tb_jmp_target_addr + a0)); > } > - s->tb_jmp_reset_offset[a0] = tcg_current_code_size(s); > + set_jmp_reset_offset(s, a0); > break; > case INDEX_op_goto_ptr: > /* jmp to the given host address (could be epilogue) */ > diff --git a/tcg/mips/tcg-target.inc.c b/tcg/mips/tcg-target.inc.c > index ca5f1d4894..cff525373b 100644 > --- a/tcg/mips/tcg-target.inc.c > +++ b/tcg/mips/tcg-target.inc.c > @@ -1744,7 +1744,7 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc, > tcg_out_opc_reg(s, OPC_JR, 0, TCG_TMP0, 0); > } > tcg_out_nop(s); > - s->tb_jmp_reset_offset[a0] = tcg_current_code_size(s); > + set_jmp_reset_offset(s, a0); > break; > case INDEX_op_goto_ptr: > /* jmp to the given host address (could be epilogue) */ > diff --git a/tcg/ppc/tcg-target.inc.c b/tcg/ppc/tcg-target.inc.c > index 86f7de5f7e..c2f729ee8f 100644 > --- a/tcg/ppc/tcg-target.inc.c > +++ b/tcg/ppc/tcg-target.inc.c > @@ -2025,10 +2025,10 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, const TCGArg *args, > } > tcg_out32(s, MTSPR | RS(TCG_REG_TB) | CTR); > tcg_out32(s, BCCTR | BO_ALWAYS); > - s->tb_jmp_reset_offset[args[0]] = c = tcg_current_code_size(s); > + set_jmp_reset_offset(s, args[0]); > if (USE_REG_TB) { > /* For the unlinked case, need to reset TCG_REG_TB. */ > - c = -c; > + c = -tcg_current_code_size(s); > assert(c == (int16_t)c); > tcg_out32(s, ADDI | TAI(TCG_REG_TB, TCG_REG_TB, c)); > } > diff --git a/tcg/s390/tcg-target.inc.c b/tcg/s390/tcg-target.inc.c > index 9af6dcef05..17c435ade5 100644 > --- a/tcg/s390/tcg-target.inc.c > +++ b/tcg/s390/tcg-target.inc.c > @@ -1783,7 +1783,7 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc, > /* and go there */ > tcg_out_insn(s, RR, BCR, S390_CC_ALWAYS, TCG_REG_TB); > } > - s->tb_jmp_reset_offset[a0] = tcg_current_code_size(s); > + set_jmp_reset_offset(s, a0); > > /* For the unlinked path of goto_tb, we need to reset > TCG_REG_TB to the beginning of this TB. */ > diff --git a/tcg/sparc/tcg-target.inc.c b/tcg/sparc/tcg-target.inc.c > index bc673bd8c6..04bdc3df5e 100644 > --- a/tcg/sparc/tcg-target.inc.c > +++ b/tcg/sparc/tcg-target.inc.c > @@ -1388,12 +1388,12 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, > tcg_out_arithi(s, TCG_REG_G0, TCG_REG_TB, 0, JMPL); > tcg_out_nop(s); > } > - s->tb_jmp_reset_offset[a0] = c = tcg_current_code_size(s); > + set_jmp_reset_offset(s, a0); > > /* For the unlinked path of goto_tb, we need to reset > TCG_REG_TB to the beginning of this TB. */ > if (USE_REG_TB) { > - c = -c; > + c = -tcg_current_code_size(s); > if (check_fit_i32(c, 13)) { > tcg_out_arithi(s, TCG_REG_TB, TCG_REG_TB, c, ARITH_ADD); > } else { > diff --git a/tcg/tcg.c b/tcg/tcg.c > index 1d1dfd7f7c..f27b22bd3c 100644 > --- a/tcg/tcg.c > +++ b/tcg/tcg.c > @@ -306,6 +306,14 @@ TCGLabel *gen_new_label(void) > return l; > } > > +static void set_jmp_reset_offset(TCGContext *s, int which) > +{ > + size_t off = tcg_current_code_size(s); > + s->tb_jmp_reset_offset[which] = off; > + /* Make sure that we didn't overflow the stored offset. */ > + assert(s->tb_jmp_reset_offset[which] == off); > +} > + > #include "tcg-target.inc.c" > > /* compare a pointer @ptr and a tb_tc @s */ > @@ -3532,7 +3540,10 @@ int tcg_gen_code(TCGContext *s, TranslationBlock *tb) > break; > case INDEX_op_insn_start: > if (num_insns >= 0) { > - s->gen_insn_end_off[num_insns] = tcg_current_code_size(s); > + size_t off = tcg_current_code_size(s); > + s->gen_insn_end_off[num_insns] = off; > + /* Assert that we do not overflow our stored offset. */ > + assert(s->gen_insn_end_off[num_insns] == off); > } > num_insns++; > for (i = 0; i < TARGET_INSN_START_WORDS; ++i) { > diff --git a/tcg/tci/tcg-target.inc.c b/tcg/tci/tcg-target.inc.c > index cc949bea85..62ed097254 100644 > --- a/tcg/tci/tcg-target.inc.c > +++ b/tcg/tci/tcg-target.inc.c > @@ -574,7 +574,7 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, const TCGArg *args, > /* Indirect jump method. */ > TODO(); > } > - s->tb_jmp_reset_offset[args[0]] = tcg_current_code_size(s); > + set_jmp_reset_offset(s, args[0]); > break; > case INDEX_op_br: > tci_out_label(s, arg_label(args[0])); > -- > 2.17.1