From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.15]) (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 EF31163A9; Sun, 7 Jul 2024 03:43:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720323794; cv=none; b=t6KZtlBrGYMOEBKFdeCHs0O3jGiiTd3w6QF2K15JMYpfyjajeT/R9CTSRIziSR8V9U42w675k4bNhZ40JJLLkoCbveWthZ+KxQpvkHjsJwBXI/Tdpn0k+YWykL4Ia9KdIUmU9PihtEK4KpiKp/vlyASWHSmPMA8nwIaVwl15/P8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720323794; c=relaxed/simple; bh=ghVROWVIc3c3/fThPWcJa4BMe5iC/W72kb0OfZCohb4=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=RLalEJGmEXklIO1mBrUr49c0YEEUporTVZ+a0RoWLacVnSvtbQdR68ZlGsAka3BrU00jRAFqM84PFsYUsdbs/dpARsT1Gg4rtSADWb8uZnRG92KJt/P16uZsq+/PQt8mVZXjED12jiD3ycXZzK6nnxedv0tGCuxCD23Am+f4fYg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=C4OxZvRQ; arc=none smtp.client-ip=192.198.163.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="C4OxZvRQ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1720323793; x=1751859793; h=date:from:to:cc:subject:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=ghVROWVIc3c3/fThPWcJa4BMe5iC/W72kb0OfZCohb4=; b=C4OxZvRQx+qPdpy1MM66XaMwJCbPtzzKgzbp4THZTnM45UnLl+jKEC68 2p2TKTpdi6x3dJAmU6VRN8MnkjHX+6T4khJGUJqDi0O+PJaGsxXXhRgxa crn01O3pHh7VvRItZewQ+vfw6gdCkjcoVSq1cCfXoymfz8TjiJOwkZgIG +4pG01sykmdo3Z/GeOYf+w3v/YaTq1YenLYRkfbSBa4QeyTLk0tR8ZSl/ dy8IeCNvWvvpwonG9YKnrUt17oIPQvVJhdvHa4mO9ghlBw9bqyDXLdmvC FRrf3UCbwz16exO59rCQXqyxeMfSZn3m4AcJq99Po7XUOglDH67cu63Yz g==; X-CSE-ConnectionGUID: 0x7JrpbQREarfkA+THOdAA== X-CSE-MsgGUID: erh0eyFLSfqy2CqpIpZ2Gw== X-IronPort-AV: E=McAfee;i="6700,10204,11125"; a="17683427" X-IronPort-AV: E=Sophos;i="6.09,189,1716274800"; d="scan'208";a="17683427" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jul 2024 20:43:12 -0700 X-CSE-ConnectionGUID: IEsGSMbYT1qNjZBdXdu9Xg== X-CSE-MsgGUID: fwRK/Zk0RL+OJ+G/vY46TA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.09,189,1716274800"; d="scan'208";a="47169545" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.54.39.125]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jul 2024 20:43:12 -0700 Date: Sat, 6 Jul 2024 20:48:26 -0700 From: Jacob Pan To: Xin Li Cc: X86 Kernel , Sean Christopherson , LKML , Thomas Gleixner , Dave Hansen , "H. Peter Anvin" , Ingo Molnar , Borislav Petkov , Xin Li , linux-perf-users@vger.kernel.org, Peter Zijlstra , Paolo Bonzini , Tony Luck , Andy Lutomirski , acme@kernel.org, kan.liang@linux.intel.com, Andi Kleen , "Mehta, Sohil" , jacob.jun.pan@linux.intel.com Subject: Re: [PATCH v3 05/11] x86/irq: Process nmi sources in NMI handler Message-ID: <20240706204826.1eda1bcd@jacob-builder> In-Reply-To: <3177880c-6538-4a18-bb2b-2926c69ef434@zytor.com> References: <20240628201839.673086-1-jacob.jun.pan@linux.intel.com> <20240628201839.673086-6-jacob.jun.pan@linux.intel.com> <3177880c-6538-4a18-bb2b-2926c69ef434@zytor.com> Organization: OTC X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 28 Jun 2024 20:39:24 -0700, Xin Li wrote: > On 6/28/2024 1:18 PM, Jacob Pan wrote: > > With NMI source reporting enabled, NMI handler can prioritize the > > handling of sources reported explicitly. If the source is unknown, then > > resume the existing processing flow. i.e. invoke all NMI handlers. > > > > Signed-off-by: Jacob Pan > > The code looks good to me, however please improve coding styles and > comments, see below. > > > > > --- > > v3: > > - Use a static flag to disable NMIs in case of HW failure > > - Optimize the case when unknown NMIs are mixed with known NMIs(HPA) > > v2: > > - Disable NMI source reporting once garbage data is given in FRED > > return stack. (HPA) > > --- > > arch/x86/kernel/nmi.c | 73 +++++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 70 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c > > index 639a34e78bc9..c3a10af7f26b 100644 > > --- a/arch/x86/kernel/nmi.c > > +++ b/arch/x86/kernel/nmi.c > > @@ -149,23 +149,90 @@ static inline int do_handle_nmi(struct nmiaction > > *a, struct pt_regs *regs, unsig return thishandled; > > } > > > > +static int nmi_handle_src(unsigned int type, struct pt_regs *regs, > > unsigned long *handled_mask) +{ > > + static bool nmi_source_disabled; > > + bool has_unknown_src = false; > > + unsigned long source_bitmask; > > + struct nmiaction *a; > > + int handled = 0; > > + int vec = 1; > > + > > + if (!cpu_feature_enabled(X86_FEATURE_NMI_SOURCE) || > > + type != NMI_LOCAL || nmi_source_disabled) > > Harder to read, no need to break into 2 lines. ok. > > + return 0; > > + > > + source_bitmask = fred_event_data(regs); > > + if (!source_bitmask) { > > unlikely()? yes. > > > + pr_warn("NMI received without source information! > > Disable source reporting.\n"); > > It sounds you're disabling some hardware functionality. Better to say, > maybe: > > Buggy hardware? Disable NMI source handling. > yes, this is more clear. > > + nmi_source_disabled = true; > > + return 0; > > + } > > + > > + /* > > + * Per NMI source specification, there is no guarantee that a > > valid > > + * NMI vector is always delivered, even when the source > > specified > > + * one. It is software's responsibility to check all available > > NMI > > + * sources when bit 0 is set in the NMI source bitmap. i.e. we > > have > > s/i.e./I.e.,/ will fix > > > + * to call every handler as if we have no NMI source. > > This comment is misleading, because you do skip NMI handlers with source > bits set in polling. At a high level, it is still accurate to say that every handler is invoked, whether by the NMI-source handling code or subsequently in the polling code. How about this: * in the NMI-source reporting bitmap. I.e. we have to call every * handler as if there is no NMI-source reporting feature enabled. * * In this case, handlers for the known NMI sources will be called * first, followed by the remaining handlers, which are called * during the subsequent polling code. > > And add an empty line to ease review. will do > > > + * On the other hand, if we do get non-zero vectors, we know > > exactly > > + * what the sources are. So we only call the handlers with the > > bit set. > > + */ > > + if (source_bitmask & BIT(NMI_SOURCE_VEC_UNKNOWN)) { > > + pr_warn_ratelimited("NMI received with unknown > > source\n"); > > s/source/sources/ > > > + has_unknown_src = true; > > + } > > + > > + rcu_read_lock(); > > Add an empty line. > > > + /* Bit 0 is for unknown NMI sources, skip it. */ > > Put "vec = 1 " close to this comment. yes > > > + for_each_set_bit_from(vec, &source_bitmask, > > NR_NMI_SOURCE_VECTORS) { > > + a = rcu_dereference(nmiaction_src_table[vec]); > > + if (!a) { > > + pr_warn_ratelimited("NMI received %d no > > handler", vec); > > Use a better log message. pr_warn_ratelimited("NMI-source vector %d has no handler!", vec); > > > + continue; > > + } > > Empty line again. will add > > > + handled += do_handle_nmi(a, regs, type); > > Ditto. yes > > > + /* > > + * Needs polling if unknown source bit is set, > > handled_mask is > > ^the got that. > > > + * used to tell the polling code which NMIs can be > > skipped. > > + */ > > + if (has_unknown_src) > > + *handled_mask |= BIT(vec); > > + } > > empty line please. will add > > > + rcu_read_unlock(); > > + > > + return handled; > > +} > > + > > static int nmi_handle(unsigned int type, struct pt_regs *regs) > > { > > struct nmi_desc *desc = nmi_to_desc(type); > > + unsigned long handled_mask = 0; > > struct nmiaction *a; > > int handled=0; > > > > - rcu_read_lock(); > > + /* > > + * Check if the NMI source handling is complete, otherwise > > polling is > > + * still required. handled_mask is non-zero if NMI source > > handling is > > + * partial due to unknown NMI sources. > > + */ > > + handled = nmi_handle_src(type, regs, &handled_mask); > > + if (handled && !handled_mask) > > + return handled; > > > > + rcu_read_lock(); > > keep original empty lines around it. ok > > > /* > > * NMIs are edge-triggered, which means if you have enough > > * of them concurrently, you can lose some because only one > > * can be latched at any given time. Walk the whole list > > * to handle those situations. > > */ > > - list_for_each_entry_rcu(a, &desc->head, list) > > + list_for_each_entry_rcu(a, &desc->head, list) { > > + /* Skip NMIs handled earlier with source info */ > > + if (BIT(a->source_vec) & handled_mask) > > + continue; > > handled += do_handle_nmi(a, regs, type); > > - > > + } > > rcu_read_unlock(); > > keep original empty lines around it. ok Thanks, Jacob