linux-kernel - [PATCH v3 32/75] x86/head/64: Reload GDT after switch to virtual addresses

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Message-Id: <20200428151725.31091-33-joro@8bytes.org>
Date:   Tue, 28 Apr 2020 17:16:42 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH v3 32/75] x86/head/64: Reload GDT after switch to virtual addresses

From: Joerg Roedel <jroedel@...e.de>

Reload the GDT after switching to virtual addresses to make sure it will
not go away when the lower mappings are removed. This will also reload
the GDT for booting APs, which will need a working GDT too to handle #VC
exceptions.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/kernel/head_64.S | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 11a28c1fb51f..20a9df062088 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -163,6 +163,11 @@ SYM_CODE_START(secondary_startup_64)
 1:
 	UNWIND_HINT_EMPTY
 
+	/* Setup boot GDT descriptor and load boot GDT */
+	leaq	boot_gdt(%rip), %rax
+	movq	%rax, boot_gdt_base(%rip)
+	lgdt	boot_gdt_descr(%rip)
+
 	/* Check if nx is implemented */
 	movl	$0x80000001, %eax
 	cpuid
-- 
2.17.1