From:   Brian Gerst <brgerst@gmail.com>
To:     linux-kernel@vger.kernel.org, x86@kernel.org
Cc:     David Woodhouse <dwmw2@infradead.org>,
        Usama Arif <usama.arif@bytedance.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Brian Gerst <brgerst@gmail.com>,
        David Woodhouse <dwmw@amazon.co.uk>
Subject: [PATCH v2 2/5] x86/smpboot: Remove early_gdt_descr on 64-bit
Date:   Fri, 24 Feb 2023 10:42:32 -0500
Message-Id: <20230224154235.277350-3-brgerst@gmail.com>
In-Reply-To: <20230224154235.277350-1-brgerst@gmail.com>
References: <20230224154235.277350-1-brgerst@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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>
---
 arch/x86/kernel/acpi/sleep.c |  2 --
 arch/x86/kernel/head_64.S    | 19 +++++++------------
 2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index 008fda8b1982..6538ddb55f28 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -114,8 +114,6 @@ int x86_acpi_suspend_lowlevel(void)
 #else /* CONFIG_64BIT */
 #ifdef CONFIG_SMP
 	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());
 	/* Force the startup into boot mode */
 	saved_smpboot_ctrl = xchg(&smpboot_control, 0);
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index f7905ba4b992..0dd57d573a0e 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -245,7 +245,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
 #ifdef CONFIG_SMP
 	/*
 	 * Is this the boot CPU coming up? If so everything is available
-	 * in initial_gs and early_gdt_descr.
+	 * in initial_gs.
 	 */
 	movl	smpboot_control(%rip), %edx
 	testl	$STARTUP_SECONDARY, %edx
@@ -313,11 +313,6 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
 	/* Save it for GS BASE setup */
 	movq	%rbx, initial_gs(%rip)
 
-	/* Calculate the GDT address */
-	movq	$gdt_page, %rcx
-	addq	%rbx, %rcx
-	movq	%rcx, early_gdt_descr_base(%rip)
-
 	movq	%rbx, %rdx
 #else
 	xorl	%edx, %edx
@@ -339,7 +334,12 @@ 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
@@ -754,11 +754,6 @@ 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
-- 
2.39.2