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[2600:6c4a:4d3f:6d5c::1019]) by smtp.gmail.com with ESMTPSA id lh10-20020a05621454ca00b0068fbe6d38f6sm949541qvb.54.2024.02.22.10.24.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Feb 2024 10:24:09 -0800 (PST) From: Brian Gerst To: linux-kernel@vger.kernel.org, x86@kernel.org Cc: Ingo Molnar , Thomas Gleixner , Borislav Petkov , "H . Peter Anvin" , Peter Zijlstra , Ard Biesheuvel , Brian Gerst Subject: [PATCH] x86/boot/64: Load kernel GDT in early boot Date: Thu, 22 Feb 2024 13:23:56 -0500 Message-ID: <20240222182356.69549-1-brgerst@gmail.com> X-Mailer: git-send-email 2.43.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Instead of loading a duplicate GDT just for early boot, load the kernel GDT from its physical address. Signed-off-by: Brian Gerst --- arch/x86/include/asm/desc.h | 1 + arch/x86/kernel/head64.c | 14 +++----------- 2 files changed, 4 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))); =20 DECLARE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page); +DECLARE_INIT_PER_CPU(gdt_page); =20 /* 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 dc0956067944..09c67e6add62 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -67,21 +67,12 @@ unsigned long vmemmap_base __ro_after_init =3D __VMEMMA= P_BASE_L4; EXPORT_SYMBOL(vmemmap_base); #endif =20 -/* - * GDT used on the boot CPU before switching to virtual addresses. - */ -static struct desc_struct startup_gdt[GDT_ENTRIES] __initdata =3D { - [GDT_ENTRY_KERNEL32_CS] =3D GDT_ENTRY_INIT(DESC_CODE32, 0, 0xffff= f), - [GDT_ENTRY_KERNEL_CS] =3D GDT_ENTRY_INIT(DESC_CODE64, 0, 0xffff= f), - [GDT_ENTRY_KERNEL_DS] =3D GDT_ENTRY_INIT(DESC_DATA64, 0, 0xffff= f), -}; - /* * Address needs to be set at runtime because it references the startup_gdt * while the kernel still uses a direct mapping. */ static struct desc_ptr startup_gdt_descr __initdata =3D { - .size =3D sizeof(startup_gdt)-1, + .size =3D GDT_SIZE - 1, .address =3D 0, }; =20 @@ -624,7 +615,8 @@ void early_setup_idt(void) void __head startup_64_setup_env(unsigned long physbase) { /* Load GDT */ - startup_gdt_descr.address =3D (unsigned long)fixup_pointer(startup_gdt, p= hysbase); + startup_gdt_descr.address =3D + (unsigned long)fixup_pointer(&init_per_cpu_var(gdt_page.gdt), physbase); native_load_gdt(&startup_gdt_descr); =20 /* New GDT is live - reload data segment registers */ base-commit: c56ac217a3c00d12e23606e0635cc95d6eb8c36a --=20 2.43.2