| /* |
| * AMD Memory Encryption Support |
| * |
| * Copyright (C) 2017 Advanced Micro Devices, Inc. |
| * |
| * Author: Tom Lendacky <thomas.lendacky@amd.com> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| */ |
| |
| #include <linux/linkage.h> |
| |
| #include <asm/processor-flags.h> |
| #include <asm/msr.h> |
| #include <asm/asm-offsets.h> |
| |
| .text |
| .code32 |
| ENTRY(get_sev_encryption_bit) |
| xor %eax, %eax |
| |
| #ifdef CONFIG_AMD_MEM_ENCRYPT |
| push %ebx |
| push %ecx |
| push %edx |
| push %edi |
| |
| /* |
| * RIP-relative addressing is needed to access the encryption bit |
| * variable. Since we are running in 32-bit mode we need this call/pop |
| * sequence to get the proper relative addressing. |
| */ |
| call 1f |
| 1: popl %edi |
| subl $1b, %edi |
| |
| movl enc_bit(%edi), %eax |
| cmpl $0, %eax |
| jge .Lsev_exit |
| |
| /* Check if running under a hypervisor */ |
| movl $1, %eax |
| cpuid |
| bt $31, %ecx /* Check the hypervisor bit */ |
| jnc .Lno_sev |
| |
| movl $0x80000000, %eax /* CPUID to check the highest leaf */ |
| cpuid |
| cmpl $0x8000001f, %eax /* See if 0x8000001f is available */ |
| jb .Lno_sev |
| |
| /* |
| * Check for the SEV feature: |
| * CPUID Fn8000_001F[EAX] - Bit 1 |
| * CPUID Fn8000_001F[EBX] - Bits 5:0 |
| * Pagetable bit position used to indicate encryption |
| */ |
| movl $0x8000001f, %eax |
| cpuid |
| bt $1, %eax /* Check if SEV is available */ |
| jnc .Lno_sev |
| |
| movl $MSR_AMD64_SEV, %ecx /* Read the SEV MSR */ |
| rdmsr |
| bt $MSR_AMD64_SEV_ENABLED_BIT, %eax /* Check if SEV is active */ |
| jnc .Lno_sev |
| |
| movl %ebx, %eax |
| andl $0x3f, %eax /* Return the encryption bit location */ |
| movl %eax, enc_bit(%edi) |
| jmp .Lsev_exit |
| |
| .Lno_sev: |
| xor %eax, %eax |
| movl %eax, enc_bit(%edi) |
| |
| .Lsev_exit: |
| pop %edi |
| pop %edx |
| pop %ecx |
| pop %ebx |
| |
| #endif /* CONFIG_AMD_MEM_ENCRYPT */ |
| |
| ret |
| ENDPROC(get_sev_encryption_bit) |
| |
| .code64 |
| ENTRY(get_sev_encryption_mask) |
| xor %rax, %rax |
| |
| #ifdef CONFIG_AMD_MEM_ENCRYPT |
| push %rbp |
| push %rdx |
| |
| movq %rsp, %rbp /* Save current stack pointer */ |
| |
| call get_sev_encryption_bit /* Get the encryption bit position */ |
| testl %eax, %eax |
| jz .Lno_sev_mask |
| |
| xor %rdx, %rdx |
| bts %rax, %rdx /* Create the encryption mask */ |
| mov %rdx, %rax /* ... and return it */ |
| |
| .Lno_sev_mask: |
| movq %rbp, %rsp /* Restore original stack pointer */ |
| |
| pop %rdx |
| pop %rbp |
| #endif |
| |
| ret |
| ENDPROC(get_sev_encryption_mask) |
| |
| .data |
| enc_bit: |
| .int 0xffffffff |
