linux-kernel - [PATCH 2/2] x86/apic: remove boot_cpu_physical

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Date:   Mon,  8 Jun 2020 17:44:49 -0700
From:   Kevin Mitchell <kevmitch@...sta.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
        Kevin Mitchell <kevmitch@...sta.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Luck <tony.luck@...el.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        David Rientjes <rientjes@...gle.com>,
        Dou Liyang <douly.fnst@...fujitsu.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] x86/apic: remove boot_cpu_physical_apicid hacks

Now that mpparse can be relied upon to not sabotage
boot_cpu_physical_apicid with nonsense, the hacks that tried to work
around that nonsense can be removed.

Signed-off-by: Kevin Mitchell <kevmitch@...sta.com>
---
 arch/x86/kernel/apic/apic.c | 30 +-----------------------------
 1 file changed, 1 insertion(+), 29 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 4b1d31be50b4..c1722a71aca5 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2361,27 +2361,8 @@ int generic_processor_info(int apicid, int version)
 	bool boot_cpu_detected = physid_isset(boot_cpu_physical_apicid,
 				phys_cpu_present_map);
 
-	/*
-	 * boot_cpu_physical_apicid is designed to have the apicid
-	 * returned by read_apic_id(), i.e, the apicid of the
-	 * currently booting-up processor. However, on some platforms,
-	 * it is temporarily modified by the apicid reported as BSP
-	 * through MP table. Concretely:
-	 *
-	 * - arch/x86/kernel/mpparse.c: MP_processor_info()
-	 * - arch/x86/mm/amdtopology.c: amd_numa_init()
-	 *
-	 * This function is executed with the modified
-	 * boot_cpu_physical_apicid. So, disabled_cpu_apicid kernel
-	 * parameter doesn't work to disable APs on kdump 2nd kernel.
-	 *
-	 * Since fixing handling of boot_cpu_physical_apicid requires
-	 * another discussion and tests on each platform, we leave it
-	 * for now and here we use read_apic_id() directly in this
-	 * function, generic_processor_info().
-	 */
 	if (disabled_cpu_apicid != BAD_APICID &&
-	    disabled_cpu_apicid != read_apic_id() &&
+	    disabled_cpu_apicid != boot_cpu_physical_apicid &&
 	    disabled_cpu_apicid == apicid) {
 		int thiscpu = num_processors + disabled_cpus;
 
@@ -2498,15 +2479,6 @@ static void __init apic_bsp_up_setup(void)
 {
 #ifdef CONFIG_X86_64
 	apic_write(APIC_ID, apic->set_apic_id(boot_cpu_physical_apicid));
-#else
-	/*
-	 * Hack: In case of kdump, after a crash, kernel might be booting
-	 * on a cpu with non-zero lapic id. But boot_cpu_physical_apicid
-	 * might be zero if read from MP tables. Get it from LAPIC.
-	 */
-# ifdef CONFIG_CRASH_DUMP
-	boot_cpu_physical_apicid = read_apic_id();
-# endif
 #endif
 	physid_set_mask_of_physid(boot_cpu_physical_apicid, &phys_cpu_present_map);
 }
-- 
2.26.2