From patchwork Tue Apr 14 11:11:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Nicholas Piggin X-Patchwork-Id: 1270235 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20161025 header.b=IyIzmXDD; dkim-atps=neutral Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 491jXt2Tzzz9sSG for ; Tue, 14 Apr 2020 21:13:50 +1000 (AEST) Received: from localhost ([::1]:58424 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jOJVk-0001BY-91 for incoming@patchwork.ozlabs.org; Tue, 14 Apr 2020 07:13:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52847) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jOJVM-00019e-6M for qemu-devel@nongnu.org; Tue, 14 Apr 2020 07:13:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jOJVK-0001mm-79 for qemu-devel@nongnu.org; Tue, 14 Apr 2020 07:13:24 -0400 Received: from mail-pl1-x641.google.com ([2607:f8b0:4864:20::641]:37247) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1jOJVJ-0001l9-VG; Tue, 14 Apr 2020 07:13:22 -0400 Received: by mail-pl1-x641.google.com with SMTP id m16so4537400pls.4; Tue, 14 Apr 2020 04:13:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=JN1UqE6+YpRxsawyrbRFyMn4vRzqFqThSa1A+kyrG+o=; b=IyIzmXDDnIi8UmpT6LSqcb6LiMSqzFsL/KxsBAsf0ptE9J9EFJKXnl49SjFGxriGVX tjLvXFkdCX0wnI7fe5Gq7UdrG1C19jQDTSqZ6OTlwdxzEkJNPn++LwZKx2Q1vdqdj6d/ Zy10RKLKk1fKZav9BFvB04dn9AbEROTxP5B5tnNTKZiiIHNZeSFww80O2/Hgy2p4xmFP ipb6JDktNwZmlIvdmsW3HUC8gCb2NDSjyKlqB1EvEq9oTPyrwSgKd0g6HrbXC4v8wSD9 DlUXJmBp8qrCL6ekQqtbG6x6StQTqfPh8shx1qjl4fFLyQp3hUu1uCOMSkmAEA+cneLz UbRw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=JN1UqE6+YpRxsawyrbRFyMn4vRzqFqThSa1A+kyrG+o=; b=oybOfjfpUgOha39l5gltL3a79atqRgvl+Axhe6yg0HaKtZQ1DVbfYbjDp4mNtctFnx NAT5Vu2pcNris5F0Xks7T0Krp2y0ATRE09F0Vm3gQsrxTsHHEkWb0OPSt7bGyaOqTk31 Ri+NzOAGrXCzqCq0lUkQbOrR/v3A15W5V044KntY4Kw9YZnC/hQssGEp6qA3PxTgSm/w SKNn5m/BNBNi9entH02zf9rSdFXghw6NjP7GQ8GCh2aLOLiwhGoRlUvdbpQcsO9sdPyV 6DFhvJLwZmDcP9rNbc3faiOPwvD7EjQLPxLKq4xE2oug7N2uMyXnBimjluBgkRRRw6Y3 sFVA== X-Gm-Message-State: AGi0PuanuRiB4jSi1ccHqFComgFP7GdM7GGYm6UXgmK6NOawe9cKXwGD mMFvylxkbCX4YdpiuxGzWmEwazKQirk= X-Google-Smtp-Source: APiQypJTyy97hXUH7vlb5EFbV8+CT0KEr49ENndCyCV/dlGiTpAT+FRcLAr9xHW/+45J/ZQYta41kg== X-Received: by 2002:a17:90a:d596:: with SMTP id v22mr26475077pju.169.1586862800008; Tue, 14 Apr 2020 04:13:20 -0700 (PDT) Received: from bobo.ozlabs.ibm.com ([203.18.28.220]) by smtp.gmail.com with ESMTPSA id u44sm10311030pgn.81.2020.04.14.04.13.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2020 04:13:19 -0700 (PDT) From: Nicholas Piggin To: qemu-devel@nongnu.org Subject: [PATCH] target/ppc: Fix mtmsr(d) L=1 variant that loses interrupts Date: Tue, 14 Apr 2020 21:11:31 +1000 Message-Id: <20200414111131.465560-1-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::641 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-stable@nongnu.org, Nicholas Piggin , =?utf-8?q?C?= =?utf-8?q?=C3=A9dric_Le_Goater?= , qemu-ppc@nongnu.org, Nathan Chancellor , Anton Blanchard , linuxppc-dev@lists.ozlabs.org, David Gibson Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" If mtmsr L=1 sets MSR[EE] while there is a maskable exception pending, it does not cause an interrupt. This causes the test case to hang: https://lists.gnu.org/archive/html/qemu-ppc/2019-10/msg00826.html More recently, Linux reduced the occurance of operations (e.g., rfi) which stop translation and allow pending interrupts to be processed. This started causing hangs in Linux boot in long-running kernel tests, running with '-d int' shows the decrementer stops firing despite DEC wrapping and MSR[EE]=1. https://lists.ozlabs.org/pipermail/linuxppc-dev/2020-April/208301.html The cause is the broken mtmsr L=1 behaviour, which is contrary to the architecture. From Power ISA v3.0B, p.977, Move To Machine State Register, Programming Note states: If MSR[EE]=0 and an External, Decrementer, or Performance Monitor exception is pending, executing an mtmsrd instruction that sets MSR[EE] to 1 will cause the interrupt to occur before the next instruction is executed, if no higher priority exception exists Fix this by handling L=1 exactly the same way as L=0, modulo the MSR bits altered. The confusion arises from L=0 being "context synchronizing" whereas L=1 is "execution synchronizing", which is a weaker semantic. However this is not a relaxation of the requirement that these exceptions cause interrupts when MSR[EE]=1 (e.g., when mtmsr executes to completion as TCG is doing here), rather it specifies how a pipelined processor can have multiple instructions in flight where one may influence how another behaves. Cc: qemu-stable@nongnu.org Reported-by: Anton Blanchard Reported-by: Nathan Chancellor Tested-by: Nathan Chancellor Signed-off-by: Nicholas Piggin Reviewed-by: Cédric Le Goater Tested-by: Cédric Le Goater --- Thanks very much to Nathan for reporting and testing it, I added his Tested-by tag despite a more polished patch, as the the basics are still the same (and still fixes his test case here). This bug possibly goes back to early v2.04 / mtmsrd L=1 support around 2007, and the code has been changed several times since then so may require some backporting. 32-bit / mtmsr untested at the moment, I don't have an environment handy. target/ppc/translate.c | 46 +++++++++++++++++++++++++----------------- 1 file changed, 27 insertions(+), 19 deletions(-) diff --git a/target/ppc/translate.c b/target/ppc/translate.c index b207fb5386..9959259dba 100644 --- a/target/ppc/translate.c +++ b/target/ppc/translate.c @@ -4361,30 +4361,34 @@ static void gen_mtmsrd(DisasContext *ctx) CHK_SV; #if !defined(CONFIG_USER_ONLY) + if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) { + gen_io_start(); + } if (ctx->opcode & 0x00010000) { - /* Special form that does not need any synchronisation */ + /* L=1 form only updates EE and RI */ TCGv t0 = tcg_temp_new(); + TCGv t1 = tcg_temp_new(); tcg_gen_andi_tl(t0, cpu_gpr[rS(ctx->opcode)], (1 << MSR_RI) | (1 << MSR_EE)); - tcg_gen_andi_tl(cpu_msr, cpu_msr, + tcg_gen_andi_tl(t1, cpu_msr, ~(target_ulong)((1 << MSR_RI) | (1 << MSR_EE))); - tcg_gen_or_tl(cpu_msr, cpu_msr, t0); + tcg_gen_or_tl(t1, t1, t0); + + gen_helper_store_msr(cpu_env, t1); tcg_temp_free(t0); + tcg_temp_free(t1); + } else { /* * XXX: we need to update nip before the store if we enter * power saving mode, we will exit the loop directly from * ppc_store_msr */ - if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) { - gen_io_start(); - } gen_update_nip(ctx, ctx->base.pc_next); gen_helper_store_msr(cpu_env, cpu_gpr[rS(ctx->opcode)]); - /* Must stop the translation as machine state (may have) changed */ - /* Note that mtmsr is not always defined as context-synchronizing */ - gen_stop_exception(ctx); } + /* Must stop the translation as machine state (may have) changed */ + gen_stop_exception(ctx); #endif /* !defined(CONFIG_USER_ONLY) */ } #endif /* defined(TARGET_PPC64) */ @@ -4394,15 +4398,23 @@ static void gen_mtmsr(DisasContext *ctx) CHK_SV; #if !defined(CONFIG_USER_ONLY) - if (ctx->opcode & 0x00010000) { - /* Special form that does not need any synchronisation */ + if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) { + gen_io_start(); + } + if (ctx->opcode & 0x00010000) { + /* L=1 form only updates EE and RI */ TCGv t0 = tcg_temp_new(); + TCGv t1 = tcg_temp_new(); tcg_gen_andi_tl(t0, cpu_gpr[rS(ctx->opcode)], (1 << MSR_RI) | (1 << MSR_EE)); - tcg_gen_andi_tl(cpu_msr, cpu_msr, + tcg_gen_andi_tl(t1, cpu_msr, ~(target_ulong)((1 << MSR_RI) | (1 << MSR_EE))); - tcg_gen_or_tl(cpu_msr, cpu_msr, t0); + tcg_gen_or_tl(t1, t1, t0); + + gen_helper_store_msr(cpu_env, t1); tcg_temp_free(t0); + tcg_temp_free(t1); + } else { TCGv msr = tcg_temp_new(); @@ -4411,9 +4423,6 @@ static void gen_mtmsr(DisasContext *ctx) * power saving mode, we will exit the loop directly from * ppc_store_msr */ - if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) { - gen_io_start(); - } gen_update_nip(ctx, ctx->base.pc_next); #if defined(TARGET_PPC64) tcg_gen_deposit_tl(msr, cpu_msr, cpu_gpr[rS(ctx->opcode)], 0, 32); @@ -4422,10 +4431,9 @@ static void gen_mtmsr(DisasContext *ctx) #endif gen_helper_store_msr(cpu_env, msr); tcg_temp_free(msr); - /* Must stop the translation as machine state (may have) changed */ - /* Note that mtmsr is not always defined as context-synchronizing */ - gen_stop_exception(ctx); } + /* Must stop the translation as machine state (may have) changed */ + gen_stop_exception(ctx); #endif }