From: Joerg Roedel <redacted>

Add a #VC exception handler which is used when the kernel still executes
in protected mode. This boot-path already uses CPUID, which will cause #VC
exceptions in an SEV-ES guest.

Signed-off-by: Joerg Roedel <redacted>
---
 arch/x86/boot/compressed/head_64.S     |  6 ++
 arch/x86/boot/compressed/mem_encrypt.S | 77 +++++++++++++++++++++++++-
 2 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 8deeec78cdb4..eadaa0a082b8 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S

@@ -34,6 +34,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/bootparam.h>
 #include <asm/desc_defs.h>
+#include <asm/trapnr.h>
 #include "pgtable.h"
 
 /*

@@ -856,6 +857,11 @@ SYM_FUNC_START(startup32_set_idt_entry)
 SYM_FUNC_END(startup32_set_idt_entry)
 
 SYM_FUNC_START(startup32_load_idt)
+	/* #VC handler */
+	leal    rva(startup32_vc_handler)(%ebp), %eax
+	movl    $X86_TRAP_VC, %edx
+	call    startup32_set_idt_entry
+
 	/* Load IDT */
 	leal	rva(boot32_idt)(%ebp), %eax
 	movl	%eax, rva(boot32_idt_desc+2)(%ebp)

diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S
index aa561795efd1..350ecb56c7e4 100644
--- a/arch/x86/boot/compressed/mem_encrypt.S
+++ b/arch/x86/boot/compressed/mem_encrypt.S

@@ -67,10 +67,85 @@ SYM_FUNC_START(get_sev_encryption_bit)
 	ret
 SYM_FUNC_END(get_sev_encryption_bit)
 
+/*
+ * Emit code to request an CPUID register from the Hypervisor using
+ * the MSR-based protocol.
+ *
+ * fn: The register containing the CPUID function
+ * reg: Register requested
+ *	1 = EAX
+ *	2 = EBX
+ *	3 = ECX
+ *	4 = EDX
+ *
+ * Result is in EDX. Jumps to .Lfail on error
+ */
+.macro	SEV_ES_REQ_CPUID fn:req reg:req