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bh=pQJ0cFB/y9cWkLzdFv+zCeeLapn0Qvop2py0VkQ2On4=; b=2NNufubwUWNAO4hG2W0gxRRkRACJj/25P+uZo1ywkAG6KEEOS1JptqLhCwfFHQnUNowcqx AgjD4UAhJs/1xHDw== From: "tip-bot2 for Thomas Gleixner" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/core] x86/idle: Sanitize X86_BUG_AMD_E400 handling Cc: Borislav Petkov , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <877cim6sis.ffs@tglx> References: <877cim6sis.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <170932612368.398.10382603040701836222.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit The following commit has been merged into the x86/core branch of tip: Commit-ID: 3b9b8e89c8e1e97c76be6abc67db702ea978d89b Gitweb: https://git.kernel.org/tip/3b9b8e89c8e1e97c76be6abc67db702ea978d89b Author: Thomas Gleixner AuthorDate: Wed, 28 Feb 2024 23:13:00 +01:00 Committer: Borislav Petkov (AMD) CommitterDate: Fri, 01 Mar 2024 21:33:05 +01:00 x86/idle: Sanitize X86_BUG_AMD_E400 handling amd_e400_idle(), the idle routine for AMD CPUs which are affected by erratum 400 violates the RCU constraints by invoking tick_broadcast_enter() and tick_broadcast_exit() after the core code has marked RCU non-idle. The functions can end up in lockdep or tracing, which rightfully triggers a RCU warning. The core code provides now a static branch conditional invocation of the broadcast functions. Remove amd_e400_idle(), enforce default_idle() and enable the static branch on affected CPUs to cure this. Reported-by: Borislav Petkov Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/877cim6sis.ffs@tglx --- arch/x86/Kconfig | 1 +- arch/x86/kernel/process.c | 42 ++++++++------------------------------ 2 files changed, 10 insertions(+), 33 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 5029862..0802653 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -147,6 +147,7 @@ config X86 select EDAC_ATOMIC_SCRUB select EDAC_SUPPORT select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC) + select GENERIC_CLOCKEVENTS_BROADCAST_IDLE if GENERIC_CLOCKEVENTS_BROADCAST select GENERIC_CLOCKEVENTS_MIN_ADJUST select GENERIC_CMOS_UPDATE select GENERIC_CPU_AUTOPROBE diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 45a9d49..5853d56 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -846,31 +846,6 @@ void __noreturn stop_this_cpu(void *dummy) } /* - * AMD Erratum 400 aware idle routine. We handle it the same way as C3 power - * states (local apic timer and TSC stop). - * - * XXX this function is completely buggered vs RCU and tracing. - */ -static void amd_e400_idle(void) -{ - /* - * We cannot use static_cpu_has_bug() here because X86_BUG_AMD_APIC_C1E - * gets set after static_cpu_has() places have been converted via - * alternatives. - */ - if (!boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) { - default_idle(); - return; - } - - tick_broadcast_enter(); - - default_idle(); - - tick_broadcast_exit(); -} - -/* * Prefer MWAIT over HALT if MWAIT is supported, MWAIT_CPUID leaf * exists and whenever MONITOR/MWAIT extensions are present there is at * least one C1 substate. @@ -890,8 +865,8 @@ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c) if (!cpu_has(c, X86_FEATURE_MWAIT)) return 0; - /* Monitor has a bug. Fallback to HALT */ - if (boot_cpu_has_bug(X86_BUG_MONITOR)) + /* Monitor has a bug or APIC stops in C1E. Fallback to HALT */ + if (boot_cpu_has_bug(X86_BUG_MONITOR) || boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) return 0; cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); @@ -942,17 +917,15 @@ void select_idle_routine(const struct cpuinfo_x86 *c) if (x86_idle_set() || boot_option_idle_override == IDLE_POLL) return; - if (boot_cpu_has_bug(X86_BUG_AMD_E400)) { - pr_info("using AMD E400 aware idle routine\n"); - static_call_update(x86_idle, amd_e400_idle); - } else if (prefer_mwait_c1_over_halt(c)) { + if (prefer_mwait_c1_over_halt(c)) { pr_info("using mwait in idle threads\n"); static_call_update(x86_idle, mwait_idle); } else if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) { pr_info("using TDX aware idle routine\n"); static_call_update(x86_idle, tdx_safe_halt); - } else + } else { static_call_update(x86_idle, default_idle); + } } void amd_e400_c1e_apic_setup(void) @@ -985,7 +958,10 @@ void __init arch_post_acpi_subsys_init(void) if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) mark_tsc_unstable("TSC halt in AMD C1E"); - pr_info("System has AMD C1E enabled\n"); + + if (IS_ENABLED(GENERIC_CLOCKEVENTS_BROADCAST_IDLE)) + static_branch_enable(&arch_needs_tick_broadcast); + pr_info("System has AMD C1E erratum E400. Workaround enabled.\n"); } static int __init idle_setup(char *str)