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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Sohil Mehta <sohil.mehta@intel.com>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     x86@kernel.org, Tom Lendacky <thomas.lendacky@amd.com>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        Arjan van de Ven <arjan@linux.intel.com>,
        Huang Rui <ray.huang@amd.com>, Juergen Gross <jgross@suse.com>,
        Dimitri Sivanich <dimitri.sivanich@hpe.com>,
        Michael Kelley <mikelley@microsoft.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Zhang Rui <rui.zhang@intel.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Feng Tang <feng.tang@intel.com>,
        Andy Shevchenko <andy@infradead.org>
Subject: Re: [patch 00/53] x86/topology: The final installment
In-Reply-To: <7ef60626-28ab-a4cc-2f24-4f35e3d946aa@intel.com>
References: <20230807130108.853357011@linutronix.de>
 <c8ca9e16-ce03-1fe0-cf9f-f6cc2302dbac@intel.com> <87h6p9l58u.ffs@tglx>
 <7ef60626-28ab-a4cc-2f24-4f35e3d946aa@intel.com>
Date:   Tue, 08 Aug 2023 22:41:51 +0200
Message-ID: <87edkdl10w.ffs@tglx>
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On Tue, Aug 08 2023 at 13:30, Sohil Mehta wrote:
> There are compile issues with the ACPI hunk.
>
>> arch/x86/kernel/acpi/boot.c: In function =E2=80=98acpi_parse_lapic=E2=80=
=99:
>> arch/x86/kernel/acpi/boot.c:250:31: error: =E2=80=98apic_id=E2=80=99 und=
eclared (first use in this function)
>>   250 |         if (has_lapic_cpus && apic_id < 0xff)
>>       |                               ^~~~~~~
>> arch/x86/kernel/acpi/boot.c:250:31: note: each undeclared identifier is =
reported only once for each function it appears in
>> arch/x86/kernel/acpi/boot.c: In function =E2=80=98acpi_parse_madt_lapic_=
entries=E2=80=99:
>> arch/x86/kernel/acpi/boot.c:1097:47: error: =E2=80=98ACPI_MADT_TYPE_LOCA=
L_LAPIC=E2=80=99 undeclared (first use in this function); did you mean =E2=
=80=98ACPI_MADT_TYPE_LOCAL_SAPIC=E2=80=99?
>>  1097 |                 count =3D acpi_table_parse_madt(ACPI_MADT_TYPE_L=
OCAL_LAPIC,
>>       |                                               ^~~~~~~~~~~~~~~~~~=
~~~~~~~~
>>       |                                               ACPI_MADT_TYPE_LOC=
AL_SAPIC
>

Duh. Yes. I just picked the thing from the list and hacked it
up. Compilable variant below.

Thanks,

        tglx
---
 arch/x86/kernel/acpi/boot.c    |   35 +++++++++++++++++------------------
 arch/x86/kernel/cpu/topology.c |    2 ++
 2 files changed, 19 insertions(+), 18 deletions(-)

--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -171,6 +171,8 @@ static bool __init acpi_is_processor_usa
 	return false;
 }
=20
+static bool has_lapic_cpus;
+
 static int __init
 acpi_parse_x2apic(union acpi_subtable_headers *header, const unsigned long=
 end)
 {
@@ -241,6 +243,14 @@ acpi_parse_lapic(union acpi_subtable_hea
 		return 0;
=20
 	/*
+	 * According to https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programm=
ing_Model.html#processor-local-x2apic-structure
+	 * when MADT provides both valid LAPIC and x2APIC entries, the APIC ID
+	 * in x2APIC must be equal or greater than 0xff.
+	 */
+	if (has_lapic_cpus && processor->id < 0xff)
+		return 0;
+
+	/*
 	 * We need to register disabled CPU as well to permit
 	 * counting disabled CPUs. This allows us to size
 	 * cpus_possible_map more accurately, to permit
@@ -1072,10 +1082,8 @@ static int __init early_acpi_parse_madt_
=20
 static int __init acpi_parse_madt_lapic_entries(void)
 {
-	int count;
 	int x2count =3D 0;
-	int ret;
-	struct acpi_subtable_proc madt_proc[2];
+	int count;
=20
 	if (!boot_cpu_has(X86_FEATURE_APIC))
 		return -ENODEV;
@@ -1084,21 +1092,12 @@ static int __init acpi_parse_madt_lapic_
 				      acpi_parse_sapic, MAX_LOCAL_APIC);
=20
 	if (!count) {
-		memset(madt_proc, 0, sizeof(madt_proc));
-		madt_proc[0].id =3D ACPI_MADT_TYPE_LOCAL_APIC;
-		madt_proc[0].handler =3D acpi_parse_lapic;
-		madt_proc[1].id =3D ACPI_MADT_TYPE_LOCAL_X2APIC;
-		madt_proc[1].handler =3D acpi_parse_x2apic;
-		ret =3D acpi_table_parse_entries_array(ACPI_SIG_MADT,
-				sizeof(struct acpi_table_madt),
-				madt_proc, ARRAY_SIZE(madt_proc), MAX_LOCAL_APIC);
-		if (ret < 0) {
-			pr_err("Error parsing LAPIC/X2APIC entries\n");
-			return ret;
-		}
-
-		count =3D madt_proc[0].count;
-		x2count =3D madt_proc[1].count;
+		count =3D acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC,
+					      acpi_parse_lapic, MAX_LOCAL_APIC);
+		if (count > 0)
+			has_lapic_cpus =3D true;
+		x2count =3D acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_X2APIC,
+						acpi_parse_x2apic, MAX_LOCAL_APIC);
 	}
 	if (!count && !x2count) {
 		pr_err("No LAPIC entries present\n");