From patchwork Mon Apr 10 08:14:22 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Li, Xin3" X-Patchwork-Id: 13206178 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41722C77B6F for ; Mon, 10 Apr 2023 08:41:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229605AbjDJIll (ORCPT ); Mon, 10 Apr 2023 04:41:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49544 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229731AbjDJIlJ (ORCPT ); Mon, 10 Apr 2023 04:41:09 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8187C270E; Mon, 10 Apr 2023 01:41:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1681116068; x=1712652068; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=AvdDrUuw1vqZ65Zb2UmH3skaRlzxRNLvEln+YufnpOQ=; b=W75aq+h2qPxmCsJEi6aoRZEqzui6zJfUF9cvOULGWMI8n1B/8hZrDOhd +/LwRTB4uBlTcXEn2ZkbqXQUmB5qUAXipb3DjF4loUxonXER6OWnMGp7M k1JKfhfOrvcA32PBwF1hr0Xh3a/MKWzOLHsdJvI3vcuj04M8lOW6FTb/b jTIaAcdT98cU5lpGi5HPVaSJPuJbF6eEdcSIEwd3tHyYRpktHOzJtuVrg Kcs9WVk34fyf4+u0ZECjVaAeUQg54dvwe83JvPjWhUWlEzei3PMZz44p4 KOdrqhC7alZQyCWsIvMZIKI1JYG+2RlhbvjOhG+KLp/+jeFZf90YUzIga A==; X-IronPort-AV: E=McAfee;i="6600,9927,10675"; a="342078043" X-IronPort-AV: E=Sophos;i="5.98,333,1673942400"; d="scan'208";a="342078043" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Apr 2023 01:41:05 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10675"; a="799436307" X-IronPort-AV: E=Sophos;i="5.98,333,1673942400"; d="scan'208";a="799436307" Received: from unknown (HELO fred..) ([172.25.112.68]) by fmsmga002.fm.intel.com with ESMTP; 10 Apr 2023 01:41:05 -0700 From: Xin Li To: linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org, andrew.cooper3@citrix.com, seanjc@google.com, pbonzini@redhat.com, ravi.v.shankar@intel.com, jiangshanlai@gmail.com, shan.kang@intel.com Subject: [PATCH v8 17/33] x86/fred: add a debug fault entry stub for FRED Date: Mon, 10 Apr 2023 01:14:22 -0700 Message-Id: <20230410081438.1750-18-xin3.li@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230410081438.1750-1-xin3.li@intel.com> References: <20230410081438.1750-1-xin3.li@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: "H. Peter Anvin (Intel)" Add a debug fault entry stub for FRED. On a FRED system, the debug trap status information (DR6) is passed on the stack, to avoid the problem of transient state. Furthermore, FRED transitions avoid a lot of ugly corner cases the handling of which can, and should be, skipped. The FRED debug trap status information saved on the stack differs from DR6 in both stickiness and polarity; it is exactly what debug_read_clear_dr6() returns, and exc_debug_user()/exc_debug_kernel() expect. Signed-off-by: H. Peter Anvin (Intel) Tested-by: Shan Kang Signed-off-by: Xin Li --- Changes since v1: * call irqentry_nmi_{enter,exit}() in both IDT and FRED debug fault kernel handler (Peter Zijlstra). --- arch/x86/include/asm/fred.h | 1 + arch/x86/kernel/traps.c | 56 +++++++++++++++++++++++++++---------- 2 files changed, 42 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h index 4ff05d350066..f670430aaa54 100644 --- a/arch/x86/include/asm/fred.h +++ b/arch/x86/include/asm/fred.h @@ -99,6 +99,7 @@ static __always_inline unsigned long fred_event_data(struct pt_regs *regs) #define DEFINE_FRED_HANDLER(f) noinstr DECLARE_FRED_HANDLER(f) typedef DECLARE_FRED_HANDLER((*fred_handler)); +DECLARE_FRED_HANDLER(fred_exc_debug); DECLARE_FRED_HANDLER(fred_exc_page_fault); #endif /* __ASSEMBLY__ */ diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index f86cd233b00b..549f7f962f8f 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -47,6 +47,7 @@ #include #include #include +#include #include #include #include @@ -1020,21 +1021,9 @@ static bool notify_debug(struct pt_regs *regs, unsigned long *dr6) return false; } -static __always_inline void exc_debug_kernel(struct pt_regs *regs, - unsigned long dr6) +static __always_inline void debug_kernel_common(struct pt_regs *regs, + unsigned long dr6) { - /* - * Disable breakpoints during exception handling; recursive exceptions - * are exceedingly 'fun'. - * - * Since this function is NOKPROBE, and that also applies to - * HW_BREAKPOINT_X, we can't hit a breakpoint before this (XXX except a - * HW_BREAKPOINT_W on our stack) - * - * Entry text is excluded for HW_BP_X and cpu_entry_area, which - * includes the entry stack is excluded for everything. - */ - unsigned long dr7 = local_db_save(); irqentry_state_t irq_state = irqentry_nmi_enter(regs); instrumentation_begin(); @@ -1062,7 +1051,8 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs, * Catch SYSENTER with TF set and clear DR_STEP. If this hit a * watchpoint at the same time then that will still be handled. */ - if ((dr6 & DR_STEP) && is_sysenter_singlestep(regs)) + if (!cpu_feature_enabled(X86_FEATURE_FRED) && + (dr6 & DR_STEP) && is_sysenter_singlestep(regs)) dr6 &= ~DR_STEP; /* @@ -1090,7 +1080,25 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs, out: instrumentation_end(); irqentry_nmi_exit(regs, irq_state); +} +static __always_inline void exc_debug_kernel(struct pt_regs *regs, + unsigned long dr6) +{ + /* + * Disable breakpoints during exception handling; recursive exceptions + * are exceedingly 'fun'. + * + * Since this function is NOKPROBE, and that also applies to + * HW_BREAKPOINT_X, we can't hit a breakpoint before this (XXX except a + * HW_BREAKPOINT_W on our stack) + * + * Entry text is excluded for HW_BP_X and cpu_entry_area, which + * includes the entry stack is excluded for everything. + */ + unsigned long dr7 = local_db_save(); + + debug_kernel_common(regs, dr6); local_db_restore(dr7); } @@ -1179,6 +1187,24 @@ DEFINE_IDTENTRY_DEBUG_USER(exc_debug) { exc_debug_user(regs, debug_read_clear_dr6()); } + +# ifdef CONFIG_X86_FRED +DEFINE_FRED_HANDLER(fred_exc_debug) +{ + /* + * The FRED debug information saved onto stack differs from + * DR6 in both stickiness and polarity; it is exactly what + * debug_read_clear_dr6() returns. + */ + unsigned long dr6 = fred_event_data(regs); + + if (user_mode(regs)) + exc_debug_user(regs, dr6); + else + debug_kernel_common(regs, dr6); +} +# endif /* CONFIG_X86_FRED */ + #else /* 32 bit does not have separate entry points. */ DEFINE_IDTENTRY_RAW(exc_debug)