From: Joerg Roedel <jroe...@suse.de>
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 <jroe...@suse.de>
---
arch/x86/boot/compressed/head_64.S | 6 ++
arch/x86/boot/compressed/mem_encrypt.S | 96 +++++++++++++++++++++++++-
2 files changed, 101 insertions(+), 1 deletion(-)
diff --git a/arch/x86/boot/compressed/head_64.S
b/arch/x86/boot/compressed/head_64.S
index 2001c3bf0748..ee448aedb8b0 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"
/*
@@ -857,6 +858,11 @@ SYM_FUNC_END(startup32_set_idt_entry)
SYM_FUNC_START(startup32_load_idt)
#ifdef CONFIG_AMD_MEM_ENCRYPT
+ /* #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..2ca056a3707c 100644
--- a/arch/x86/boot/compressed/mem_encrypt.S
+++ b/arch/x86/boot/compressed/mem_encrypt.S
@@ -67,10 +67,104 @@ SYM_FUNC_START(get_sev_encryption_bit)
ret
SYM_FUNC_END(get_sev_encryption_bit)
+/**
+ * sev_es_req_cpuid - Request a CPUID value from the Hypervisor using
+ * the GHCB MSR protocol
+ *
+ * @%eax: Register to request (0=EAX, 1=EBX, 2=ECX, 3=EDX)
+ * @%edx: CPUID Function
+ *
+ * Returns 0 in %eax on sucess, non-zero on failure
+ * %edx returns CPUID value on success
+ */
+SYM_CODE_START_LOCAL(sev_es_req_cpuid)
+ shll $30, %eax
+ orl $0x00000004, %eax
+ movl $MSR_AMD64_SEV_ES_GHCB, %ecx
+ wrmsr
+ rep; vmmcall # VMGEXIT
+ rdmsr
+
+ /* Check response */
+ movl %eax, %ecx
+ andl $0x3ffff000, %ecx # Bits [12-29] MBZ
+ jnz 2f
+
+ /* Check return code */
+ andl $0xfff, %eax
+ cmpl $5, %eax
+ jne 2f
+
+ /* All good - return success */
+ xorl %eax, %eax
+1:
+ ret
+2:
+ movl $-1, %eax
+ jmp 1b
+SYM_CODE_END(sev_es_req_cpuid)
+
+SYM_CODE_START(startup32_vc_handler)
+ pushl %eax
+ pushl %ebx
+ pushl %ecx
+ pushl %edx
+
+ /* Keep CPUID function in %ebx */
+ movl %eax, %ebx
+
+ /* Check if error-code == SVM_EXIT_CPUID */
+ cmpl $0x72, 16(%esp)
+ jne .Lfail
+
+ movl $0, %eax # Request CPUID[fn].EAX
+ movl %ebx, %edx # CPUID fn
+ call sev_es_req_cpuid # Call helper
+ testl %eax, %eax # Check return code
+ jnz .Lfail
+ movl %edx, 12(%esp) # Store result
+
+ movl $1, %eax # Request CPUID[fn].EBX
+ movl %ebx, %edx # CPUID fn
+ call sev_es_req_cpuid # Call helper
+ testl %eax, %eax # Check return code
+ jnz .Lfail
+ movl %edx, 8(%esp) # Store result
+
+ movl $2, %eax # Request CPUID[fn].ECX
+ movl %ebx, %edx # CPUID fn
+ call sev_es_req_cpuid # Call helper
+ testl %eax, %eax # Check return code
+ jnz .Lfail
+ movl %edx, 4(%esp) # Store result
+
+ movl $3, %eax # Request CPUID[fn].EDX
+ movl %ebx, %edx # CPUID fn
+ call sev_es_req_cpuid # Call helper
+ testl %eax, %eax # Check return code
+ jnz .Lfail
+ movl %edx, 0(%esp) # Store result
+
+ popl %edx
+ popl %ecx
+ popl %ebx
+ popl %eax
+
+ /* Remove error code */
+ addl $4, %esp
+
+ /* Jump over CPUID instruction */
+ addl $2, (%esp)
+
+ iret
+.Lfail:
+ hlt
+ jmp .Lfail
+SYM_CODE_END(startup32_vc_handler)
+
.code64
#include "../../kernel/sev_verify_cbit.S"
-
SYM_FUNC_START(set_sev_encryption_mask)
#ifdef CONFIG_AMD_MEM_ENCRYPT
push %rbp
--
2.30.1
