linux-kernel - [tip:x86/asm] x86/vdso: Initialize the CPU/node NR segment descriptor earlier

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Message-ID: <tip-b2e2ba578e016a091eb31565849990fe68c7c599@git.kernel.org>
Date:   Mon, 8 Oct 2018 02:58:47 -0700
From:   "tip-bot for Chang S. Bae" <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     luto@...nel.org, riel@...riel.com, ravi.v.shankar@...el.com,
        markus.t.metzger@...el.com, mingo@...nel.org,
        chang.seok.bae@...el.com, hpa@...or.com, peterz@...radead.org,
        dvlasenk@...hat.com, linux-kernel@...r.kernel.org,
        dave.hansen@...ux.intel.com, luto@...capital.net,
        tglx@...utronix.de, brgerst@...il.com,
        torvalds@...ux-foundation.org, bp@...en8.de
Subject: [tip:x86/asm] x86/vdso: Initialize the CPU/node NR segment
 descriptor earlier

Commit-ID:  b2e2ba578e016a091eb31565849990fe68c7c599
Gitweb:     https://git.kernel.org/tip/b2e2ba578e016a091eb31565849990fe68c7c599
Author:     Chang S. Bae <chang.seok.bae@...el.com>
AuthorDate: Tue, 18 Sep 2018 16:08:59 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 8 Oct 2018 10:41:10 +0200

x86/vdso: Initialize the CPU/node NR segment descriptor earlier

Currently the CPU/node NR segment descriptor (GDT_ENTRY_CPU_NUMBER) is
initialized relatively late during CPU init, from the vCPU code, which
has a number of disadvantages, such as hotplug CPU notifiers and SMP
cross-calls.

Instead just initialize it much earlier, directly in cpu_init().

This reduces complexity and increases robustness.

[ mingo: Wrote new changelog. ]

Suggested-by: H. Peter Anvin <hpa@...or.com>
Suggested-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Markus T Metzger <markus.t.metzger@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ravi Shankar <ravi.v.shankar@...el.com>
Cc: Rik van Riel <riel@...riel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1537312139-5580-9-git-send-email-chang.seok.bae@intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/entry/vdso/vma.c    | 33 +--------------------------------
 arch/x86/kernel/cpu/common.c | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 39b5584c5808..3f9d43f26f63 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -332,35 +332,6 @@ static __init int vdso_setup(char *s)
 	return 0;
 }
 __setup("vdso=", vdso_setup);
-#endif
-
-#ifdef CONFIG_X86_64
-static void vgetcpu_cpu_init(void *arg)
-{
-	int cpu = smp_processor_id();
-	struct desc_struct d = { };
-	unsigned long cpudata = vdso_encode_cpu_node(cpu, cpu_to_node(cpu));
-
-	if (static_cpu_has(X86_FEATURE_RDTSCP))
-		write_rdtscp_aux(cpudata);
-
-	/* Store CPU and node number in limit */
-	d.limit0 = cpudata;
-	d.limit1 = cpudata >> 16;
-
-	d.type = 5;		/* RO data, expand down, accessed */
-	d.dpl = 3;		/* Visible to user code */
-	d.s = 1;		/* Not a system segment */
-	d.p = 1;		/* Present */
-	d.d = 1;		/* 32-bit */
-
-	write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_CPU_NUMBER, &d, DESCTYPE_S);
-}
-
-static int vgetcpu_online(unsigned int cpu)
-{
-	return smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);
-}
 
 static int __init init_vdso(void)
 {
@@ -370,9 +341,7 @@ static int __init init_vdso(void)
 	init_vdso_image(&vdso_image_x32);
 #endif
 
-	/* notifier priority > KVM */
-	return cpuhp_setup_state(CPUHP_AP_X86_VDSO_VMA_ONLINE,
-				 "x86/vdso/vma:online", vgetcpu_online, NULL);
+	return 0;
 }
 subsys_initcall(init_vdso);
 #endif /* CONFIG_X86_64 */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 44c4ef3d989b..a148d18a1ef0 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1669,6 +1669,29 @@ static void wait_for_master_cpu(int cpu)
 #endif
 }
 
+#ifdef CONFIG_X86_64
+static void setup_getcpu(int cpu)
+{
+	unsigned long cpudata = vdso_encode_cpu_node(cpu, early_cpu_to_node(cpu));
+	struct desc_struct d = { };
+
+	if (static_cpu_has(X86_FEATURE_RDTSCP))
+		write_rdtscp_aux(cpudata);
+
+	/* Store CPU and node number in limit. */
+	d.limit0 = cpudata;
+	d.limit1 = cpudata >> 16;
+
+	d.type = 5;		/* RO data, expand down, accessed */
+	d.dpl = 3;		/* Visible to user code */
+	d.s = 1;		/* Not a system segment */
+	d.p = 1;		/* Present */
+	d.d = 1;		/* 32-bit */
+
+	write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_CPU_NUMBER, &d, DESCTYPE_S);
+}
+#endif
+
 /*
  * cpu_init() initializes state that is per-CPU. Some data is already
  * initialized (naturally) in the bootstrap process, such as the GDT
@@ -1706,6 +1729,7 @@ void cpu_init(void)
 	    early_cpu_to_node(cpu) != NUMA_NO_NODE)
 		set_numa_node(early_cpu_to_node(cpu));
 #endif
+	setup_getcpu(cpu);
 
 	me = current;