linux-kernel - [PATCH v2 1/2] x86: Enable x2apic during resume from suspend if used previously

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Date:   Thu, 26 Oct 2023 12:03:29 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>
CC:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        "Namhyung Kim" <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        "Len Brown" <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Sandipan Das <sandipan.das@....com>,
        "open list:PERFORMANCE EVENTS SUBSYSTEM" 
        <linux-perf-users@...r.kernel.org>,
        "open list:PERFORMANCE EVENTS SUBSYSTEM" 
        <linux-kernel@...r.kernel.org>,
        "open list:SUSPEND TO RAM" <linux-pm@...r.kernel.org>,
        "open list:ACPI" <linux-acpi@...r.kernel.org>,
        Mario Limonciello <mario.limonciello@....com>
Subject: [PATCH v2 1/2] x86: Enable x2apic during resume from suspend if used previously

If x2apic was enabled during boot with parallel startup
it will be needed during resume from suspend to ram as well.

Store whether to enable into the smpboot_control global variable
and during startup re-enable it if necessary.

This fixes resume from suspend on workstation CPUs with x2apic
enabled.

It will also work on systems with one maxcpus=1 but still using
x2apic since x2apic is also re-enabled in lapic_resume().

Cc: stable@...r.kernel.org # 6.5
Fixes: 0c7ffa32dbd6 ("x86/smpboot/64: Implement arch_cpuhp_init_parallel_bringup() and enable it")
Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
v1->v2:
 * Clarify it's in workstations in commit message
 * Fix style issues in comment and curly braces
---
 arch/x86/include/asm/smp.h   |  1 +
 arch/x86/kernel/acpi/sleep.c | 13 +++++++++----
 arch/x86/kernel/head_64.S    | 15 +++++++++++++++
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index c31c633419fe..86584ffaebc3 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -190,6 +190,7 @@ extern unsigned long apic_mmio_base;
 #endif /* !__ASSEMBLY__ */
 
 /* Control bits for startup_64 */
+#define STARTUP_ENABLE_X2APIC	0x40000000
 #define STARTUP_READ_APICID	0x80000000
 
 /* Top 8 bits are reserved for control */
diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index 6dfecb27b846..10d8921b4bb8 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -11,6 +11,7 @@
 #include <linux/dmi.h>
 #include <linux/cpumask.h>
 #include <linux/pgtable.h>
+#include <asm/apic.h>
 #include <asm/segment.h>
 #include <asm/desc.h>
 #include <asm/cacheflush.h>
@@ -129,12 +130,16 @@ int x86_acpi_suspend_lowlevel(void)
 	 */
 	current->thread.sp = (unsigned long)temp_stack + sizeof(temp_stack);
 	/*
-	 * Ensure the CPU knows which one it is when it comes back, if
-	 * it isn't in parallel mode and expected to work that out for
-	 * itself.
+	 * Ensure x2apic is re-enabled if necessary and the CPU knows which
+	 * one it is when it comes back, if it isn't in parallel mode and
+	 * expected to work that out for itself.
 	 */
-	if (!(smpboot_control & STARTUP_PARALLEL_MASK))
+	if (smpboot_control & STARTUP_PARALLEL_MASK) {
+		if (x2apic_enabled())
+			smpboot_control |= STARTUP_ENABLE_X2APIC;
+	} else {
 		smpboot_control = smp_processor_id();
+	}
 #endif
 	initial_code = (unsigned long)wakeup_long64;
 	saved_magic = 0x123456789abcdef0L;
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index ea6995920b7a..300901af9fa3 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -237,9 +237,14 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
 	 * CPU number is encoded in smpboot_control.
 	 *
 	 * Bit 31	STARTUP_READ_APICID (Read APICID from APIC)
+	 * Bit 30	STARTUP_ENABLE_X2APIC (Enable X2APIC mode)
 	 * Bit 0-23	CPU# if STARTUP_xx flags are not set
 	 */
 	movl	smpboot_control(%rip), %ecx
+
+	testl	$STARTUP_ENABLE_X2APIC, %ecx
+	jnz	.Lenable_x2apic
+
 	testl	$STARTUP_READ_APICID, %ecx
 	jnz	.Lread_apicid
 	/*
@@ -249,6 +254,16 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
 	andl	$(~STARTUP_PARALLEL_MASK), %ecx
 	jmp	.Lsetup_cpu
 
+.Lenable_x2apic:
+	/* Enable X2APIC if disabled */
+	mov	$MSR_IA32_APICBASE, %ecx
+	rdmsr
+	testl	$X2APIC_ENABLE, %eax
+	jnz	.Lread_apicid_msr
+	orl	$X2APIC_ENABLE, %eax
+	wrmsr
+	jmp	.Lread_apicid_msr
+
 .Lread_apicid:
 	/* Check whether X2APIC mode is already enabled */
 	mov	$MSR_IA32_APICBASE, %ecx
-- 
2.34.1