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Message-ID: <20240226220544.70769-1-brgerst@gmail.com>
Date: Mon, 26 Feb 2024 17:05:44 -0500
From: Brian Gerst <brgerst@...il.com>
To: linux-kernel@...r.kernel.org,
x86@...nel.org
Cc: Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>,
"H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Ard Biesheuvel <ardb@...nel.org>,
Brian Gerst <brgerst@...il.com>
Subject: [PATCH v2] x86/boot/64: Load kernel GDT in early boot
Instead of loading a duplicate GDT just for early boot, load the kernel
GDT from its physical address.
Signed-off-by: Brian Gerst <brgerst@...il.com>
---
v2: Updated to latest tip tree
arch/x86/include/asm/desc.h | 1 +
arch/x86/kernel/head64.c | 13 ++-----------
2 files changed, 3 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index ec95fe44fa3a..62dc9f59ea76 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -46,6 +46,7 @@ struct gdt_page {
} __attribute__((aligned(PAGE_SIZE)));
DECLARE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page);
+DECLARE_INIT_PER_CPU(gdt_page);
/* Provide the original GDT */
static inline struct desc_struct *get_cpu_gdt_rw(unsigned int cpu)
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 72351c3121a6..fd77a266f29d 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -68,15 +68,6 @@ unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE_L4;
EXPORT_SYMBOL(vmemmap_base);
#endif
-/*
- * GDT used on the boot CPU before switching to virtual addresses.
- */
-static struct desc_struct startup_gdt[GDT_ENTRIES] __initdata = {
- [GDT_ENTRY_KERNEL32_CS] = GDT_ENTRY_INIT(DESC_CODE32, 0, 0xfffff),
- [GDT_ENTRY_KERNEL_CS] = GDT_ENTRY_INIT(DESC_CODE64, 0, 0xfffff),
- [GDT_ENTRY_KERNEL_DS] = GDT_ENTRY_INIT(DESC_DATA64, 0, 0xfffff),
-};
-
#ifdef CONFIG_X86_5LEVEL
static void __head *fixup_pointer(void *ptr, unsigned long physaddr)
{
@@ -589,8 +580,8 @@ void __head startup_64_setup_gdt_idt(void)
void *handler = NULL;
struct desc_ptr startup_gdt_descr = {
- .address = (unsigned long)&RIP_REL_REF(startup_gdt),
- .size = sizeof(startup_gdt) - 1,
+ .address = (unsigned long)&RIP_REL_REF(init_per_cpu_var(gdt_page.gdt)),
+ .size = GDT_SIZE - 1,
};
/* Load GDT */
base-commit: afb9cce6ad6e808cf659f43925941be96f61b9c9
--
2.43.2
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