linux-kernel - [RFC PATCH 02/15] x86/apic: Fix smp init delay for extended Intel families

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Message-ID: <20241220213711.1892696-3-sohil.mehta@intel.com>
Date: Fri, 20 Dec 2024 21:36:57 +0000
From: Sohil Mehta <sohil.mehta@...el.com>
To: x86@...nel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Tony Luck <tony.luck@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	"H . Peter Anvin" <hpa@...or.com>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Zhang Rui <rui.zhang@...el.com>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	linux-pm@...r.kernel.org,
	linux-hwmon@...r.kernel.org
Subject: [RFC PATCH 02/15] x86/apic: Fix smp init delay for extended Intel families

The MP specification version 1.4 references the i486 and early Pentium
processors in family 5. However, all processors starting with family 6
likely do not need the 10 msec INIT delay. The omission of the Pentium
4s (family 15) seems like an oversight in the original check.

With some risk, choose a simpler check and extend the quirk to all
recent and upcoming Intel processors.

While at it, fix the command line parameter comment to match with the
actual name.

Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
---
 arch/x86/kernel/smpboot.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index b5a8f0891135..6c98e9178963 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -668,7 +668,7 @@ static void impress_friends(void)
  * But that slows boot and resume on modern processors, which include
  * many cores and don't require that delay.
  *
- * Cmdline "init_cpu_udelay=" is available to over-ride this delay.
+ * Cmdline "cpu_init_udelay=" is available to override this delay.
  * Modern processor families are quirked to remove the delay entirely.
  */
 #define UDELAY_10MS_DEFAULT 10000
@@ -690,9 +690,9 @@ static void __init smp_quirk_init_udelay(void)
 		return;
 
 	/* if modern processor, use no delay */
-	if (((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) && (boot_cpu_data.x86 == 6)) ||
-	    ((boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) && (boot_cpu_data.x86 >= 0x18)) ||
-	    ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && (boot_cpu_data.x86 >= 0xF))) {
+	if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL && boot_cpu_data.x86_vfm >= INTEL_PENTIUM_PRO) ||
+	    (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON && boot_cpu_data.x86 >= 0x18) ||
+	    (boot_cpu_data.x86_vendor == X86_VENDOR_AMD && boot_cpu_data.x86 >= 0xF)) {
 		init_udelay = 0;
 		return;
 	}
-- 
2.43.0