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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* AMD Memory Encryption Support
*
* Copyright (C) 2017 Advanced Micro Devices, Inc.
*
* Author: Tom Lendacky <thomas.lendacky@amd.com>
*/
#include <linux/linkage.h>
#include <asm/processor-flags.h>
#include <asm/msr.h>
#include <asm/asm-offsets.h>
.text
.code32
SYM_FUNC_START(get_sev_encryption_bit)
xor %eax, %eax
#ifdef CONFIG_AMD_MEM_ENCRYPT
push %ebx
push %ecx
push %edx
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 */
jmp .Lsev_exit
.Lno_sev:
xor %eax, %eax
.Lsev_exit:
pop %edx
pop %ecx
pop %ebx
#endif /* CONFIG_AMD_MEM_ENCRYPT */
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 success, 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
/*
* Sanity check CPUID results from the Hypervisor. See comment in
* do_vc_no_ghcb() for more details on why this is necessary.
*/
/* Fail if SEV leaf not available in CPUID[0x80000000].EAX */
cmpl $0x80000000, %ebx
jne .Lcheck_sev
cmpl $0x8000001f, 12(%esp)
jb .Lfail
jmp .Ldone
.Lcheck_sev:
/* Fail if SEV bit not set in CPUID[0x8000001f].EAX[1] */
cmpl $0x8000001f, %ebx
jne .Ldone
btl $1, 12(%esp)
jnc .Lfail
.Ldone:
popl %edx
popl %ecx
popl %ebx
popl %eax
/* Remove error code */
addl $4, %esp
/* Jump over CPUID instruction */
addl $2, (%esp)
iret
.Lfail:
/* Send terminate request to Hypervisor */
movl $0x100, %eax
xorl %edx, %edx
movl $MSR_AMD64_SEV_ES_GHCB, %ecx
wrmsr
rep; vmmcall
/* If request fails, go to hlt loop */
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
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
bts %rax, sme_me_mask(%rip) /* Create the encryption mask */
/*
* Read MSR_AMD64_SEV again and store it to sev_status. Can't do this in
* get_sev_encryption_bit() because this function is 32-bit code and
* shared between 64-bit and 32-bit boot path.
*/
movl $MSR_AMD64_SEV, %ecx /* Read the SEV MSR */
rdmsr
/* Store MSR value in sev_status */
shlq $32, %rdx
orq %rdx, %rax
movq %rax, sev_status(%rip)
.Lno_sev_mask:
movq %rbp, %rsp /* Restore original stack pointer */
pop %rdx
pop %rbp
#endif
xor %rax, %rax
RET
SYM_FUNC_END(set_sev_encryption_mask)
.data
#ifdef CONFIG_AMD_MEM_ENCRYPT
.balign 8
SYM_DATA(sme_me_mask, .quad 0)
SYM_DATA(sev_status, .quad 0)
SYM_DATA(sev_check_data, .quad 0)
#endif
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