[PATCH v2 1/7] x86/boot/compressed/64: Cleanup exception handling before booting kernel

[Joerg Roedel]

From: Joerg Roedel <jroe...@suse.de>

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 <jroe...@suse.de>
---
 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);
-- 
2.30.1