From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C264E7469 for ; Sun, 17 Sep 2023 20:25:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31155C433C8; Sun, 17 Sep 2023 20:25:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1694982345; bh=0YGOQaKOmSZetTWVpuMPRCg3YoOB3wA1MMLmoONH/B8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rf3p6jvsp2UrjcQsVGJCDnIOnhIGSHIRaa7R9fblPsnE+w+9z9s66PG3yFMCBXFJ5 LEF352Lw4T07eGcT9ow0V6Hr0v6xyEMc/bCoblPdd06j9cInuVE4nmtnv1SwZ/uFSk py1po+E1uddKysk+52MqWnaueTQSbOqytv0FCtFA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Russell Currey , Michael Ellerman , Sasha Levin Subject: [PATCH 5.15 224/511] powerpc/pseries: Rework lppaca_shared_proc() to avoid DEBUG_PREEMPT Date: Sun, 17 Sep 2023 21:10:51 +0200 Message-ID: <20230917191119.218102256@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230917191113.831992765@linuxfoundation.org> References: <20230917191113.831992765@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Russell Currey [ Upstream commit eac030b22ea12cdfcbb2e941c21c03964403c63f ] lppaca_shared_proc() takes a pointer to the lppaca which is typically accessed through get_lppaca(). With DEBUG_PREEMPT enabled, this leads to checking if preemption is enabled, for example: BUG: using smp_processor_id() in preemptible [00000000] code: grep/10693 caller is lparcfg_data+0x408/0x19a0 CPU: 4 PID: 10693 Comm: grep Not tainted 6.5.0-rc3 #2 Call Trace: dump_stack_lvl+0x154/0x200 (unreliable) check_preemption_disabled+0x214/0x220 lparcfg_data+0x408/0x19a0 ... This isn't actually a problem however, as it does not matter which lppaca is accessed, the shared proc state will be the same. vcpudispatch_stats_procfs_init() already works around this by disabling preemption, but the lparcfg code does not, erroring any time /proc/powerpc/lparcfg is accessed with DEBUG_PREEMPT enabled. Instead of disabling preemption on the caller side, rework lppaca_shared_proc() to not take a pointer and instead directly access the lppaca, bypassing any potential preemption checks. Fixes: f13c13a00512 ("powerpc: Stop using non-architected shared_proc field in lppaca") Signed-off-by: Russell Currey [mpe: Rework to avoid needing a definition in paca.h and lppaca.h] Signed-off-by: Michael Ellerman Link: https://msgid.link/20230823055317.751786-4-mpe@ellerman.id.au Signed-off-by: Sasha Levin --- arch/powerpc/include/asm/lppaca.h | 11 +++++++++-- arch/powerpc/platforms/pseries/lpar.c | 10 +--------- arch/powerpc/platforms/pseries/lparcfg.c | 4 ++-- arch/powerpc/platforms/pseries/setup.c | 2 +- drivers/cpuidle/cpuidle-pseries.c | 8 +------- 5 files changed, 14 insertions(+), 21 deletions(-) diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h index 5d509ba0550b5..1412e643122e4 100644 --- a/arch/powerpc/include/asm/lppaca.h +++ b/arch/powerpc/include/asm/lppaca.h @@ -45,6 +45,7 @@ #include #include #include +#include /* * The lppaca is the "virtual processor area" registered with the hypervisor, @@ -123,14 +124,20 @@ struct lppaca { */ #define LPPACA_OLD_SHARED_PROC 2 -static inline bool lppaca_shared_proc(struct lppaca *l) +#ifdef CONFIG_PPC_PSERIES +/* + * All CPUs should have the same shared proc value, so directly access the PACA + * to avoid false positives from DEBUG_PREEMPT. + */ +static inline bool lppaca_shared_proc(void) { + struct lppaca *l = local_paca->lppaca_ptr; + if (!firmware_has_feature(FW_FEATURE_SPLPAR)) return false; return !!(l->__old_status & LPPACA_OLD_SHARED_PROC); } -#ifdef CONFIG_PPC_PSERIES #define get_lppaca() (get_paca()->lppaca_ptr) #endif diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 3df6bdfea475a..d133597a84ca0 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -638,16 +638,8 @@ static const struct proc_ops vcpudispatch_stats_freq_proc_ops = { static int __init vcpudispatch_stats_procfs_init(void) { - /* - * Avoid smp_processor_id while preemptible. All CPUs should have - * the same value for lppaca_shared_proc. - */ - preempt_disable(); - if (!lppaca_shared_proc(get_lppaca())) { - preempt_enable(); + if (!lppaca_shared_proc()) return 0; - } - preempt_enable(); if (!proc_create("powerpc/vcpudispatch_stats", 0600, NULL, &vcpudispatch_stats_proc_ops)) diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c index f71eac74ea92a..19503a8797823 100644 --- a/arch/powerpc/platforms/pseries/lparcfg.c +++ b/arch/powerpc/platforms/pseries/lparcfg.c @@ -205,7 +205,7 @@ static void parse_ppp_data(struct seq_file *m) ppp_data.active_system_procs); /* pool related entries are appropriate for shared configs */ - if (lppaca_shared_proc(get_lppaca())) { + if (lppaca_shared_proc()) { unsigned long pool_idle_time, pool_procs; seq_printf(m, "pool=%d\n", ppp_data.pool_num); @@ -529,7 +529,7 @@ static int pseries_lparcfg_data(struct seq_file *m, void *v) partition_potential_processors); seq_printf(m, "shared_processor_mode=%d\n", - lppaca_shared_proc(get_lppaca())); + lppaca_shared_proc()); #ifdef CONFIG_PPC_BOOK3S_64 seq_printf(m, "slb_size=%d\n", mmu_slb_size); diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c index c2b3752684b5f..d25053755c8b8 100644 --- a/arch/powerpc/platforms/pseries/setup.c +++ b/arch/powerpc/platforms/pseries/setup.c @@ -816,7 +816,7 @@ static void __init pSeries_setup_arch(void) if (firmware_has_feature(FW_FEATURE_LPAR)) { vpa_init(boot_cpuid); - if (lppaca_shared_proc(get_lppaca())) { + if (lppaca_shared_proc()) { static_branch_enable(&shared_processor); pv_spinlocks_init(); } diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c index 7e7ab5597d7ac..0590001db6532 100644 --- a/drivers/cpuidle/cpuidle-pseries.c +++ b/drivers/cpuidle/cpuidle-pseries.c @@ -410,13 +410,7 @@ static int __init pseries_idle_probe(void) return -ENODEV; if (firmware_has_feature(FW_FEATURE_SPLPAR)) { - /* - * Use local_paca instead of get_lppaca() since - * preemption is not disabled, and it is not required in - * fact, since lppaca_ptr does not need to be the value - * associated to the current CPU, it can be from any CPU. - */ - if (lppaca_shared_proc(local_paca->lppaca_ptr)) { + if (lppaca_shared_proc()) { cpuidle_state_table = shared_states; max_idle_state = ARRAY_SIZE(shared_states); } else { -- 2.40.1