1/*
  2 * AMD Memory Encryption Support
  3 *
  4 * Copyright (C) 2017 Advanced Micro Devices, Inc.
  5 *
  6 * Author: Tom Lendacky <thomas.lendacky@amd.com>
  7 *
  8 * This program is free software; you can redistribute it and/or modify
  9 * it under the terms of the GNU General Public License version 2 as
 10 * published by the Free Software Foundation.
 11 */
 12
 13#include <linux/linkage.h>
 14
 15#include <asm/processor-flags.h>
 16#include <asm/msr.h>
 17#include <asm/asm-offsets.h>
 18
 19	.text
 20	.code32
 21ENTRY(get_sev_encryption_bit)
 22	xor	%eax, %eax
 23
 24#ifdef CONFIG_AMD_MEM_ENCRYPT
 25	push	%ebx
 26	push	%ecx
 27	push	%edx
 28	push	%edi
 29
 30	/*
 31	 * RIP-relative addressing is needed to access the encryption bit
 32	 * variable. Since we are running in 32-bit mode we need this call/pop
 33	 * sequence to get the proper relative addressing.
 34	 */
 35	call	1f
 361:	popl	%edi
 37	subl	$1b, %edi
 38
 39	movl	enc_bit(%edi), %eax
 40	cmpl	$0, %eax
 41	jge	.Lsev_exit
 42
 43	/* Check if running under a hypervisor */
 44	movl	$1, %eax
 45	cpuid
 46	bt	$31, %ecx		/* Check the hypervisor bit */
 47	jnc	.Lno_sev
 48
 49	movl	$0x80000000, %eax	/* CPUID to check the highest leaf */
 50	cpuid
 51	cmpl	$0x8000001f, %eax	/* See if 0x8000001f is available */
 52	jb	.Lno_sev
 53
 54	/*
 55	 * Check for the SEV feature:
 56	 *   CPUID Fn8000_001F[EAX] - Bit 1
 57	 *   CPUID Fn8000_001F[EBX] - Bits 5:0
 58	 *     Pagetable bit position used to indicate encryption
 59	 */
 60	movl	$0x8000001f, %eax
 61	cpuid
 62	bt	$1, %eax		/* Check if SEV is available */
 63	jnc	.Lno_sev
 64
 65	movl	$MSR_AMD64_SEV, %ecx	/* Read the SEV MSR */
 66	rdmsr
 67	bt	$MSR_AMD64_SEV_ENABLED_BIT, %eax	/* Check if SEV is active */
 68	jnc	.Lno_sev
 69
 70	movl	%ebx, %eax
 71	andl	$0x3f, %eax		/* Return the encryption bit location */
 72	movl	%eax, enc_bit(%edi)
 73	jmp	.Lsev_exit
 74
 75.Lno_sev:
 76	xor	%eax, %eax
 77	movl	%eax, enc_bit(%edi)
 78
 79.Lsev_exit:
 80	pop	%edi
 81	pop	%edx
 82	pop	%ecx
 83	pop	%ebx
 84
 85#endif	/* CONFIG_AMD_MEM_ENCRYPT */
 86
 87	ret
 88ENDPROC(get_sev_encryption_bit)
 89
 90	.code64
 91ENTRY(set_sev_encryption_mask)
 92#ifdef CONFIG_AMD_MEM_ENCRYPT
 93	push	%rbp
 94	push	%rdx
 95
 96	movq	%rsp, %rbp		/* Save current stack pointer */
 97
 98	call	get_sev_encryption_bit	/* Get the encryption bit position */
 99	testl	%eax, %eax
100	jz	.Lno_sev_mask
101
102	bts	%rax, sme_me_mask(%rip)	/* Create the encryption mask */
103
104.Lno_sev_mask:
105	movq	%rbp, %rsp		/* Restore original stack pointer */
106
107	pop	%rdx
108	pop	%rbp
109#endif
110
111	xor	%rax, %rax
112	ret
113ENDPROC(set_sev_encryption_mask)
114
115	.data
116enc_bit:
117	.int	0xffffffff
118
119#ifdef CONFIG_AMD_MEM_ENCRYPT
120	.balign	8
121GLOBAL(sme_me_mask)
122	.quad	0
123#endif