From: Joerg Roedel <jroedel@xxxxxxx> 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 <jroedel@xxxxxxx> --- 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 + /* Request CPUID[%ebx].EAX */ + movl $\reg, %eax + shll $30, %eax + orl $0x00000004, %eax + movl \fn, %edx + movl $MSR_AMD64_SEV_ES_GHCB, %ecx + wrmsr + rep; vmmcall + rdmsr + /* Check response code */ + andl $0xfff, %eax + cmpl $5, %eax + jne .Lfail + /* All good */ +.endm + +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 + + /* Request CPUID[%ebx].EAX */ + SEV_ES_REQ_CPUID fn=%ebx reg=0 + movl %edx, 12(%esp) + + /* Request CPUID[%ebx].EBX */ + SEV_ES_REQ_CPUID fn=%ebx reg=1 + movl %edx, 8(%esp) + + /* Request CPUID[%ebx].ECX */ + SEV_ES_REQ_CPUID fn=%ebx reg=2 + movl %edx, 4(%esp) + + /* Request CPUID[%ebx].EDX */ + SEV_ES_REQ_CPUID fn=%ebx reg=3 + movl %edx, (%esp) + + 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 -- 2.30.0
