From:   Usama Arif <usama.arif@bytedance.com>
To:     dwmw2@infradead.org, tglx@linutronix.de, kim.phillips@amd.com,
        brgerst@gmail.com
Cc:     piotrgorski@cachyos.org, oleksandr@natalenko.name,
        arjan@linux.intel.com, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org,
        pbonzini@redhat.com, paulmck@kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        rcu@vger.kernel.org, mimoja@mimoja.de, hewenliang4@huawei.com,
        thomas.lendacky@amd.com, seanjc@google.com, pmenzel@molgen.mpg.de,
        fam.zheng@bytedance.com, punit.agrawal@bytedance.com,
        simon.evans@bytedance.com, liangma@liangbit.com,
        David Woodhouse <dwmw@amazon.co.uk>,
        Usama Arif <usama.arif@bytedance.com>,
        "Guilherme G . Piccoli" <gpiccoli@igalia.com>
Subject: [PATCH v14 07/12] x86/smpboot: Remove early_gdt_descr on 64-bit
Date:   Wed,  8 Mar 2023 17:13:23 +0000
Message-Id: <20230308171328.1562857-8-usama.arif@bytedance.com>
In-Reply-To: <20230308171328.1562857-1-usama.arif@bytedance.com>
References: <20230308171328.1562857-1-usama.arif@bytedance.com>
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From: Brian Gerst <brgerst@gmail.com>

Build the GDT descriptor on the stack instead.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Tested-by: Usama Arif <usama.arif@bytedance.com>
Signed-off-by: Usama Arif <usama.arif@bytedance.com>
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
---
 arch/x86/kernel/acpi/sleep.c |  2 --
 arch/x86/kernel/head_64.S    | 11 ++++++-----
 arch/x86/kernel/smpboot.c    |  2 +-
 3 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index 1b4c43d0819a..de89bb4719d0 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -127,8 +127,6 @@ int x86_acpi_suspend_lowlevel(void)
 	 * value is in the actual %rsp register.
 	 */
 	current->thread.sp = (unsigned long)temp_stack + sizeof(temp_stack);
-	early_gdt_descr.address =
-			(unsigned long)get_cpu_gdt_rw(smp_processor_id());
 	initial_gs = per_cpu_offset(smp_processor_id());
 	smpboot_control = smp_processor_id();
 #endif
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index cc1b145055ac..a5b46c2fba05 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -265,7 +265,12 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
 	 * addresses where we're currently running on. We have to do that here
 	 * because in 32bit we couldn't load a 64bit linear address.
 	 */
-	lgdt	early_gdt_descr(%rip)
+	subq	$16, %rsp
+	movw	$(GDT_SIZE-1), (%rsp)
+	leaq	gdt_page(%rdx), %rax
+	movq	%rax, 2(%rsp)
+	lgdt	(%rsp)
+	addq	$16, %rsp
 
 	/* set up data segments */
 	xorl %eax,%eax
@@ -667,10 +672,6 @@ SYM_DATA_END(level1_fixmap_pgt)
 	.data
 	.align 16
 
-SYM_DATA(early_gdt_descr,		.word GDT_ENTRIES*8-1)
-SYM_DATA_LOCAL(early_gdt_descr_base,	.quad INIT_PER_CPU_VAR(gdt_page))
-
-	.align 16
 SYM_DATA(smpboot_control,		.long 0)
 
 	.align 16
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 62e3bf37f0b8..a22460a07cf8 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1110,10 +1110,10 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle,
 		start_ip = real_mode_header->trampoline_start64;
 #endif
 	idle->thread.sp = (unsigned long)task_pt_regs(idle);
-	early_gdt_descr.address = (unsigned long)get_cpu_gdt_rw(cpu);
 	initial_code = (unsigned long)start_secondary;
 
 	if (IS_ENABLED(CONFIG_X86_32)) {
+		early_gdt_descr.address = (unsigned long)get_cpu_gdt_rw(cpu);
 		initial_stack  = idle->thread.sp;
 	} else {
 		smpboot_control = cpu;
-- 
2.25.1