From b099155e2df7dadf8b1ad9828158b89f5639f654 Mon Sep 17 00:00:00 2001
From: Joerg Roedel <jroedel@suse.de>
Date: Wed, 10 Mar 2021 09:43:19 +0100
Subject: [PATCH] x86/boot/compressed/64: Cleanup exception handling before
 booting kernel

Disable the exception handling before booting the kernel to make sure
any exceptions that happen during early kernel boot are not directed to
the pre-decompression code.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210312123824.306-2-joro@8bytes.org
---
 arch/x86/boot/compressed/idt_64.c | 14 ++++++++++++++
 arch/x86/boot/compressed/misc.c   |  7 ++-----
 arch/x86/boot/compressed/misc.h   |  6 ++++++
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/compressed/idt_64.c b/arch/x86/boot/compressed/idt_64.c
index 804a502ee0d2..9b93567d663a 100644
--- a/arch/x86/boot/compressed/idt_64.c
+++ b/arch/x86/boot/compressed/idt_64.c
@@ -52,3 +52,17 @@ void load_stage2_idt(void)
 
 	load_boot_idt(&boot_idt_desc);
 }
+
+void cleanup_exception_handling(void)
+{
+	/*
+	 * Flush GHCB from cache and map it encrypted again when running as
+	 * SEV-ES guest.
+	 */
+	sev_es_shutdown_ghcb();
+
+	/* Set a null-idt, disabling #PF and #VC handling */
+	boot_idt_desc.size    = 0;
+	boot_idt_desc.address = 0;
+	load_boot_idt(&boot_idt_desc);
+}
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 267e7f93050e..cc9fd0e8766a 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -443,11 +443,8 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 	handle_relocations(output, output_len, virt_addr);
 	debug_putstr("done.\nBooting the kernel.\n");
 
-	/*
-	 * Flush GHCB from cache and map it encrypted again when running as
-	 * SEV-ES guest.
-	 */
-	sev_es_shutdown_ghcb();
+	/* Disable exception handling before booting the kernel */
+	cleanup_exception_handling();
 
 	return output;
 }
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 901ea5ebec22..e5612f035498 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -155,6 +155,12 @@ extern pteval_t __default_kernel_pte_mask;
 extern gate_desc boot_idt[BOOT_IDT_ENTRIES];
 extern struct desc_ptr boot_idt_desc;
 
+#ifdef CONFIG_X86_64
+void cleanup_exception_handling(void);
+#else
+static inline void cleanup_exception_handling(void) { }
+#endif
+
 /* IDT Entry Points */
 void boot_page_fault(void);
 void boot_stage1_vc(void);