From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33134) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1chD0c-0008Gn-EW for qemu-devel@nongnu.org; Fri, 24 Feb 2017 05:21:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1chD0Y-0001SE-Cf for qemu-devel@nongnu.org; Fri, 24 Feb 2017 05:21:54 -0500 Received: from mail-wr0-x22a.google.com ([2a00:1450:400c:c0c::22a]:36444) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1chD0Y-0001Qd-2K for qemu-devel@nongnu.org; Fri, 24 Feb 2017 05:21:50 -0500 Received: by mail-wr0-x22a.google.com with SMTP id 89so10027895wrr.3 for ; Fri, 24 Feb 2017 02:21:49 -0800 (PST) References: <1487914949-1294-1-git-send-email-bobby.prani@gmail.com> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <1487914949-1294-1-git-send-email-bobby.prani@gmail.com> Date: Fri, 24 Feb 2017 10:21:46 +0000 Message-ID: <87y3wvlwhx.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH v2] mttcg/i386: Patch instruction using async_safe_* framework List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Pranith Kumar Cc: qemu-devel@nongnu.org, Richard Henderson , Peter Maydell Pranith Kumar writes: > In mttcg, calling pause_all_vcpus() during execution from the > generated TBs causes a deadlock if some vCPU is waiting for exclusive > execution in start_exclusive(). Fix this by using the aync_safe_* > framework instead of pausing vcpus for patching instructions. > > CC: Richard Henderson > CC: Peter Maydell > CC: Alex Bennée > Signed-off-by: Pranith Kumar > --- > hw/i386/kvmvapic.c | 82 ++++++++++++++++++++++++++++++++++-------------------- > 1 file changed, 52 insertions(+), 30 deletions(-) > > diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c > index 82a4955..11b0d49 100644 > --- a/hw/i386/kvmvapic.c > +++ b/hw/i386/kvmvapic.c > @@ -383,8 +383,7 @@ static void patch_byte(X86CPU *cpu, target_ulong addr, uint8_t byte) > cpu_memory_rw_debug(CPU(cpu), addr, &byte, 1, 1); > } > > -static void patch_call(VAPICROMState *s, X86CPU *cpu, target_ulong ip, > - uint32_t target) > +static void patch_call(X86CPU *cpu, target_ulong ip, uint32_t target) > { > uint32_t offset; > > @@ -393,23 +392,24 @@ static void patch_call(VAPICROMState *s, X86CPU *cpu, target_ulong ip, > cpu_memory_rw_debug(CPU(cpu), ip + 1, (void *)&offset, sizeof(offset), 1); > } > > -static void patch_instruction(VAPICROMState *s, X86CPU *cpu, target_ulong ip) > +struct PatchInfo { > + VAPICHandlers *handler; > + target_ulong ip; > +}; > + > +static void do_patch_instruction(CPUState *cs, run_on_cpu_data data) > { > - CPUState *cs = CPU(cpu); > - CPUX86State *env = &cpu->env; > - VAPICHandlers *handlers; > + X86CPU *x86_cpu = X86_CPU(cs); > + CPUX86State *env = &x86_cpu->env; > + struct PatchInfo *info = (struct PatchInfo *) data.host_ptr; > + VAPICHandlers *handlers = info->handler; > + target_ulong ip = info->ip; > uint8_t opcode[2]; > uint32_t imm32 = 0; > target_ulong current_pc = 0; > target_ulong current_cs_base = 0; > uint32_t current_flags = 0; > > - if (smp_cpus == 1) { > - handlers = &s->rom_state.up; > - } else { > - handlers = &s->rom_state.mp; > - } > - > if (!kvm_enabled()) { > cpu_get_tb_cpu_state(env, ¤t_pc, ¤t_cs_base, > ¤t_flags); > @@ -421,48 +421,70 @@ static void patch_instruction(VAPICROMState *s, X86CPU *cpu, target_ulong ip) > } > } > > - pause_all_vcpus(); > - > cpu_memory_rw_debug(cs, ip, opcode, sizeof(opcode), 0); > > switch (opcode[0]) { > case 0x89: /* mov r32 to r/m32 */ > - patch_byte(cpu, ip, 0x50 + modrm_reg(opcode[1])); /* push reg */ > - patch_call(s, cpu, ip + 1, handlers->set_tpr); > + patch_byte(x86_cpu, ip, 0x50 + modrm_reg(opcode[1])); /* push reg */ > + patch_call(x86_cpu, ip + 1, handlers->set_tpr); > break; > case 0x8b: /* mov r/m32 to r32 */ > - patch_byte(cpu, ip, 0x90); > - patch_call(s, cpu, ip + 1, handlers->get_tpr[modrm_reg(opcode[1])]); > + patch_byte(x86_cpu, ip, 0x90); > + patch_call(x86_cpu, ip + 1, handlers->get_tpr[modrm_reg(opcode[1])]); > break; > case 0xa1: /* mov abs to eax */ > - patch_call(s, cpu, ip, handlers->get_tpr[0]); > + patch_call(x86_cpu, ip, handlers->get_tpr[0]); > break; > case 0xa3: /* mov eax to abs */ > - patch_call(s, cpu, ip, handlers->set_tpr_eax); > + patch_call(x86_cpu, ip, handlers->set_tpr_eax); > break; > case 0xc7: /* mov imm32, r/m32 (c7/0) */ > - patch_byte(cpu, ip, 0x68); /* push imm32 */ > + patch_byte(x86_cpu, ip, 0x68); /* push imm32 */ > cpu_memory_rw_debug(cs, ip + 6, (void *)&imm32, sizeof(imm32), 0); > cpu_memory_rw_debug(cs, ip + 1, (void *)&imm32, sizeof(imm32), 1); > - patch_call(s, cpu, ip + 5, handlers->set_tpr); > + patch_call(x86_cpu, ip + 5, handlers->set_tpr); > break; > case 0xff: /* push r/m32 */ > - patch_byte(cpu, ip, 0x50); /* push eax */ > - patch_call(s, cpu, ip + 1, handlers->get_tpr_stack); > + patch_byte(x86_cpu, ip, 0x50); /* push eax */ > + patch_call(x86_cpu, ip + 1, handlers->get_tpr_stack); > break; > default: > abort(); > } > > - resume_all_vcpus(); > + g_free(info); > +} > + > +static void patch_instruction(VAPICROMState *s, X86CPU *cpu, target_ulong ip) > +{ > + CPUState *cs = CPU(cpu); > + VAPICHandlers *handlers; > + struct PatchInfo *info; > + > + if (smp_cpus == 1) { > + handlers = &s->rom_state.up; > + } else { > + handlers = &s->rom_state.mp; > + } > + > + info = g_new(struct PatchInfo, 1); > + info->handler = handlers; > + info->ip = ip; > > if (!kvm_enabled()) { > - /* Both tb_lock and iothread_mutex will be reset when > - * longjmps back into the cpu_exec loop. */ > - tb_lock(); > - tb_gen_code(cs, current_pc, current_cs_base, current_flags, 1); > - cpu_loop_exit_noexc(cs); > + const run_on_cpu_func fn = do_patch_instruction; > + > + async_safe_run_on_cpu(cs, fn, RUN_ON_CPU_HOST_PTR(info)); > + cs->exception_index = EXCP_INTERRUPT; > + cpu_loop_exit(cs); > } > + > + pause_all_vcpus(); > + > + do_patch_instruction(cs, RUN_ON_CPU_HOST_PTR(info)); > + > + resume_all_vcpus(); > + g_free(info); I don't know if there is any benefit scheduling this as async work for KVM but I'll leave that up to Paolo to decide. From a TCG point of view I think its good: Reviewed-by: Alex Bennée > } > > void vapic_report_tpr_access(DeviceState *dev, CPUState *cs, target_ulong ip, -- Alex Bennée