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 3F57F2E03E6 for ; Tue, 15 Jul 2025 12:37:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752583079; cv=none; b=NDXrpmTR2mtyJ66tGVoaa+kksokPPwKTFtSug566t4sBIDsXD18Ku/IGNubaDBqmCGOe0jla+F6p4ipuu1yU4GJLwYnwkMsRaQLtcudTKLLU+uIgbsLG42nBwKbOdMPf8B1UhoAbNz5PPPgS7C7uU3LjnqIUQW7X1yWMbZVhs9w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752583079; c=relaxed/simple; bh=3U8CioD//EHXa4TGtNQG4LsvdJb9pJ1awimIt098WcI=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bJ05T836ApxHJ5mph+naUYr/Prg3WX0Dcv22iOxf4GSF1mp6zTJsCj2Z9Ef4iDkE7ga4jFWtZOJr7hSX9+H+AvxdMyy0cRHITszzOtROPncmyxNYgJ2pTwbgzGL5kQqR1VE8V9BhMCoAVXrQrZ+4z6cc8gtKuKINKREru82wtRg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MDkqOVvv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MDkqOVvv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30D7FC4CEF1; Tue, 15 Jul 2025 12:37:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752583078; bh=3U8CioD//EHXa4TGtNQG4LsvdJb9pJ1awimIt098WcI=; h=From:To:Subject:Date:In-Reply-To:References:From; b=MDkqOVvvsO11DKbJEW6Bu2hKw5bNQWnQMpbsVlxBN67llhuf6UasK0X/QTku9HoxI zfZMXi0ztYDdDOnS8hAXRk7kP2mQX4tK09wl7tzPP4SplyclPJKWyOSMcklpa3xh8x c7Cz99dXAD9UM4wBl2/yXJz2U9PcC6QQZU3u+ToP/BSN/Zq6vnJnke7gJHP1JuLCiC L1GdVW0YqaOJERUk9lOTGmJ4KDAjFPIbrfyGgeoTwyIL8eP+rtXu/fkrClLBiRNUHJ NKCkBNWBsxAf+cwmeNrwFJ760wEVL67pMdHMqVAlSrJrn5VZXDBm8QTtU4KGRSAXW2 Qb4QZAyZWCRhw== From: Borislav Petkov To: Subject: [PATCH 5/5] x86/process: Move the buffer clearing before MONITOR Date: Tue, 15 Jul 2025 14:37:49 +0200 Message-ID: <20250715123749.4610-6-bp@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250715123749.4610-1-bp@kernel.org> References: <20250715123749.4610-1-bp@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Borislav Petkov (AMD)" Commit 8e786a85c0a3c0fffae6244733fb576eeabd9dec upstream. Move the VERW clearing before the MONITOR so that VERW doesn't disarm it and the machine never enters C1. Original idea by Kim Phillips . Suggested-by: Andrew Cooper Signed-off-by: Borislav Petkov (AMD) --- arch/x86/include/asm/mwait.h | 16 +++++++++++----- arch/x86/kernel/process.c | 15 ++++++++++++--- 2 files changed, 23 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index 20b33e6370c3..2a2de4f3cb20 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -43,8 +43,6 @@ static inline void __monitorx(const void *eax, unsigned long ecx, static inline void __mwait(unsigned long eax, unsigned long ecx) { - x86_idle_clear_cpu_buffers(); - /* "mwait %eax, %ecx;" */ asm volatile(".byte 0x0f, 0x01, 0xc9;" :: "a" (eax), "c" (ecx)); @@ -88,7 +86,6 @@ static inline void __mwaitx(unsigned long eax, unsigned long ebx, static inline void __sti_mwait(unsigned long eax, unsigned long ecx) { - x86_idle_clear_cpu_buffers(); /* "mwait %eax, %ecx;" */ asm volatile("sti; .byte 0x0f, 0x01, 0xc9;" @@ -107,6 +104,11 @@ static inline void __sti_mwait(unsigned long eax, unsigned long ecx) */ static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx) { + if (need_resched()) + return; + + x86_idle_clear_cpu_buffers(); + if (static_cpu_has_bug(X86_BUG_MONITOR) || !current_set_polling_and_test()) { if (static_cpu_has_bug(X86_BUG_CLFLUSH_MONITOR)) { mb(); @@ -115,9 +117,13 @@ static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx) } __monitor((void *)¤t_thread_info()->flags, 0, 0); - if (!need_resched()) - __mwait(eax, ecx); + if (need_resched()) + goto out; + + __mwait(eax, ecx); } + +out: current_clr_polling(); } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 38c517a786f4..8f984b553590 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -819,6 +819,11 @@ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c) */ static __cpuidle void mwait_idle(void) { + if (need_resched()) + return; + + x86_idle_clear_cpu_buffers(); + if (!current_set_polling_and_test()) { if (this_cpu_has(X86_BUG_CLFLUSH_MONITOR)) { mb(); /* quirk */ @@ -827,13 +832,17 @@ static __cpuidle void mwait_idle(void) } __monitor((void *)¤t_thread_info()->flags, 0, 0); - if (!need_resched()) - __sti_mwait(0, 0); - else + if (need_resched()) { raw_local_irq_enable(); + goto out; + } + + __sti_mwait(0, 0); } else { raw_local_irq_enable(); } + +out: __current_clr_polling(); } -- 2.43.0