From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8EDDF17A305; Tue, 14 Oct 2025 22:54:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760482473; cv=none; b=LbA7buyG22vfFHqqNtOUXy0vVHVaHJOWU1XalC8JzgeURshrr8tvdNtwm8M19Rny+unJbOl9N+p7vXZx7fMilnPTthdlsfUaXo+C/NPyIj/T9F3UFHFlXwThRECQRjzLSFu/SQODuM69vRodHN4fcDXOqUE3pYa3uxtnrGDGTG0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760482473; c=relaxed/simple; bh=Eaw+QU5vhaHi+5xYUVnUTpSyuKHE4vIJbktJ0ZtgiUc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=dSgjV8IM1HPJqhWJFqHJM59p1Pz8s354VU+LyIT+H6qco0cyB58Wo5zfUQSh497qBDicAvd41ixfD9yRK8uzuA824oyXViPrZ3gg+GVEhQKHoR47Xgk4b685MDuAQpeTO6TjhrYk9Dci7IaOj9IGNvESykUw2M7hjrrjUdkC90Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 926CB1A32; Tue, 14 Oct 2025 15:54:21 -0700 (PDT) Received: from [192.168.20.16] (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E989F3F66E; Tue, 14 Oct 2025 15:54:24 -0700 (PDT) Message-ID: <57719c05-6470-40c8-8ecf-daa4ad1006da@arm.com> Date: Tue, 14 Oct 2025 17:54:14 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ACPI: PPTT: Dump PPTT table when error detected To: Feng Tang , "Rafael J . Wysocki" , Len Brown , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Sudeep Holla , James Morse References: <20251014085154.59557-1-feng.tang@linux.alibaba.com> Content-Language: en-US From: Jeremy Linton In-Reply-To: <20251014085154.59557-1-feng.tang@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi, On 10/14/25 3:51 AM, Feng Tang wrote: > There was warning message about PPTT table: > "ACPI PPTT: PPTT table found, but unable to locate core 1 (1)", > and it in turn caused scheduler warnings when building up the system. > It took a while to root cause the problem be related a broken PPTT > table which has wrong cache information. > > To speedup debugging similar issues, dump the PPTT table when there > is warning about it. > > The dumped info on a ARM server is like: > > ACPI PPTT: Processors: > P[ 0][0x0024]: parent=0x0000 acpi_proc_id= 0 num_res=1 flags=0x11(package) > P[ 1][0x005a]: parent=0x0024 acpi_proc_id= 0 num_res=1 flags=0x12() > P[ 2][0x008a]: parent=0x005a acpi_proc_id= 0 num_res=3 flags=0x1a(leaf) > P[ 3][0x00f2]: parent=0x005a acpi_proc_id= 1 num_res=3 flags=0x1a(leaf) > P[ 4][0x015a]: parent=0x005a acpi_proc_id= 2 num_res=3 flags=0x1a(leaf) > ... > ACPI PPTT: Caches: > C[ 0][0x0072]: flags=0x7f next_level=0x0000 size=0x4000000 sets=65536 way=16 attribute=0xa line_size=64 > C[ 1][0x00aa]: flags=0x7f next_level=0x00da size=0x10000 sets=256 way=4 attribute=0x4 line_size=64 > C[ 2][0x00c2]: flags=0x7f next_level=0x00da size=0x10000 sets=256 way=4 attribute=0x2 line_size=64 > C[ 3][0x00da]: flags=0x7f next_level=0x0000 size=0x100000 sets=2048 way=8 attribute=0xa line_size=64 This is an interesting idea, particularly if the dump is smarter and acts like a linter, but i'm not sure the output right now would have helped with the original problem. In that respect simply sprinkling a lot of pr_debug information around during the parsing might be more helpful to understand the context around parse errors. I was under the impression doing that was frowned on, as I ended up removing quite a number of them during the initial reviews. I wonder if simply print_hex_dump'ing the table on certain errors with some acpi=debug like option is just as useful. Particularly if someone writes a better userspace pptt pretty printer, since the iasl output isn't helpful to understand the tree relationships. > ... > > From it, we can see the processor/cache info and the hierarchy relation > between them. > > Signed-off-by: Feng Tang > --- > drivers/acpi/pptt.c | 75 +++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 75 insertions(+) > > diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c > index 54676e3d82dd..e7b48a77a12f 100644 > --- a/drivers/acpi/pptt.c > +++ b/drivers/acpi/pptt.c > @@ -498,6 +498,79 @@ static void acpi_pptt_warn_missing(void) > pr_warn_once("No PPTT table found, CPU and cache topology may be inaccurate\n"); > } > > +static void acpi_dump_pptt_table(struct acpi_table_header *table_hdr) > +{ > + struct acpi_subtable_header *entry, *entry_start; > + unsigned long end; > + struct acpi_pptt_processor *cpu; > + struct acpi_pptt_cache *cache; > + u32 entry_sz, i; > + u8 len; > + static bool dumped; > + > + /* PPTT table could be pretty big, no need to dump it twice */ > + if (dumped) > + return; > + dumped = true; > + > + end = (unsigned long)table_hdr + table_hdr->length; > + entry_start = ACPI_ADD_PTR(struct acpi_subtable_header, table_hdr, > + sizeof(struct acpi_table_pptt)); > + > + pr_info("Processors:\n"); > + entry_sz = sizeof(struct acpi_pptt_processor); > + entry = entry_start; > + i = 0; > + while ((unsigned long)entry + entry_sz <= end) { > + len = entry->length; > + if (!len) { > + pr_warn("Invalid zero length subtable\n"); > + return; > + } > + > + cpu = (struct acpi_pptt_processor *)entry; > + entry = ACPI_ADD_PTR(struct acpi_subtable_header, entry, len); > + > + if (cpu->header.type != ACPI_PPTT_TYPE_PROCESSOR) > + continue; > + > + printk(KERN_INFO "P[%3d][0x%04lx]: parent=0x%04x acpi_proc_id=%3d num_res=%d flags=0x%02x(%s%s%s)\n", > + i++, (unsigned long)cpu - (unsigned long)table_hdr, > + cpu->parent, cpu->acpi_processor_id, > + cpu->number_of_priv_resources, cpu->flags, > + cpu->flags & ACPI_PPTT_PHYSICAL_PACKAGE ? "package" : "", > + cpu->flags & ACPI_PPTT_ACPI_LEAF_NODE ? "leaf" : "", > + cpu->flags & ACPI_PPTT_ACPI_PROCESSOR_IS_THREAD ? ", thread" : "" > + ); > + > + } > + > + pr_info("Caches:\n"); > + entry_sz = sizeof(struct acpi_pptt_cache); > + entry = entry_start; > + i = 0; > + while ((unsigned long)entry + entry_sz <= end) { > + len = entry->length; > + if (!len) { > + pr_warn("Invalid zero length subtable\n"); > + return; > + } > + > + cache = (struct acpi_pptt_cache *)entry; > + entry = ACPI_ADD_PTR(struct acpi_subtable_header, entry, len); > + > + if (cache->header.type != ACPI_PPTT_TYPE_CACHE) > + continue; > + > + printk(KERN_INFO "C[%4d][0x%04lx]: flags=0x%02x next_level=0x%04x size=0x%-8x sets=%-6d way=%-2d attribute=0x%-2x line_size=%d\n", > + i++, (unsigned long)cache - (unsigned long)table_hdr, > + cache->flags, cache->next_level_of_cache, cache->size, > + cache->number_of_sets, cache->associativity, > + cache->attributes, cache->line_size > + ); > + } > +} > + > /** > * topology_get_acpi_cpu_tag() - Find a unique topology value for a feature > * @table: Pointer to the head of the PPTT table > @@ -534,6 +607,8 @@ static int topology_get_acpi_cpu_tag(struct acpi_table_header *table, > } > pr_warn_once("PPTT table found, but unable to locate core %d (%d)\n", > cpu, acpi_cpu_id); > + > + acpi_dump_pptt_table(table); > return -ENOENT; > } >