Commit 26a4ef7e authored by Linus Torvalds's avatar Linus Torvalds

Merge tag 'x86_seves_for_v5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 AMD secure virtualization (SEV-ES) updates from Borislav Petkov:
 "Add support for SEV-ES guests booting through the 32-bit boot path,
  along with cleanups, fixes and improvements"

* tag 'x86_seves_for_v5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/sev-es: Optimize __sev_es_ist_enter() for better readability
  x86/sev-es: Replace open-coded hlt-loops with sev_es_terminate()
  x86/boot/compressed/64: Check SEV encryption in the 32-bit boot-path
  x86/boot/compressed/64: Add CPUID sanity check to 32-bit boot-path
  x86/boot/compressed/64: Add 32-bit boot #VC handler
  x86/boot/compressed/64: Setup IDT in startup_32 boot path
  x86/boot/compressed/64: Reload CS in startup_32
  x86/sev: Do not require Hypervisor CPUID bit for SEV guests
  x86/boot/compressed/64: Cleanup exception handling before booting kernel
  x86/virtio: Have SEV guests enforce restricted virtio memory access
  x86/sev-es: Remove subtraction of res variable
parents 98ee795b 799de1ba
...@@ -1519,6 +1519,7 @@ config AMD_MEM_ENCRYPT ...@@ -1519,6 +1519,7 @@ config AMD_MEM_ENCRYPT
select ARCH_USE_MEMREMAP_PROT select ARCH_USE_MEMREMAP_PROT
select ARCH_HAS_FORCE_DMA_UNENCRYPTED select ARCH_HAS_FORCE_DMA_UNENCRYPTED
select INSTRUCTION_DECODER select INSTRUCTION_DECODER
select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
help help
Say yes to enable support for the encryption of system memory. Say yes to enable support for the encryption of system memory.
This requires an AMD processor that supports Secure Memory This requires an AMD processor that supports Secure Memory
......
...@@ -34,6 +34,7 @@ ...@@ -34,6 +34,7 @@
#include <asm/asm-offsets.h> #include <asm/asm-offsets.h>
#include <asm/bootparam.h> #include <asm/bootparam.h>
#include <asm/desc_defs.h> #include <asm/desc_defs.h>
#include <asm/trapnr.h>
#include "pgtable.h" #include "pgtable.h"
/* /*
...@@ -107,9 +108,19 @@ SYM_FUNC_START(startup_32) ...@@ -107,9 +108,19 @@ SYM_FUNC_START(startup_32)
movl %eax, %gs movl %eax, %gs
movl %eax, %ss movl %eax, %ss
/* setup a stack and make sure cpu supports long mode. */ /* Setup a stack and load CS from current GDT */
leal rva(boot_stack_end)(%ebp), %esp leal rva(boot_stack_end)(%ebp), %esp
pushl $__KERNEL32_CS
leal rva(1f)(%ebp), %eax
pushl %eax
lretl
1:
/* Setup Exception handling for SEV-ES */
call startup32_load_idt
/* Make sure cpu supports long mode. */
call verify_cpu call verify_cpu
testl %eax, %eax testl %eax, %eax
jnz .Lno_longmode jnz .Lno_longmode
...@@ -172,11 +183,21 @@ SYM_FUNC_START(startup_32) ...@@ -172,11 +183,21 @@ SYM_FUNC_START(startup_32)
*/ */
call get_sev_encryption_bit call get_sev_encryption_bit
xorl %edx, %edx xorl %edx, %edx
#ifdef CONFIG_AMD_MEM_ENCRYPT
testl %eax, %eax testl %eax, %eax
jz 1f jz 1f
subl $32, %eax /* Encryption bit is always above bit 31 */ subl $32, %eax /* Encryption bit is always above bit 31 */
bts %eax, %edx /* Set encryption mask for page tables */ bts %eax, %edx /* Set encryption mask for page tables */
/*
* Mark SEV as active in sev_status so that startup32_check_sev_cbit()
* will do a check. The sev_status memory will be fully initialized
* with the contents of MSR_AMD_SEV_STATUS later in
* set_sev_encryption_mask(). For now it is sufficient to know that SEV
* is active.
*/
movl $1, rva(sev_status)(%ebp)
1: 1:
#endif
/* Initialize Page tables to 0 */ /* Initialize Page tables to 0 */
leal rva(pgtable)(%ebx), %edi leal rva(pgtable)(%ebx), %edi
...@@ -261,6 +282,9 @@ SYM_FUNC_START(startup_32) ...@@ -261,6 +282,9 @@ SYM_FUNC_START(startup_32)
movl %esi, %edx movl %esi, %edx
1: 1:
#endif #endif
/* Check if the C-bit position is correct when SEV is active */
call startup32_check_sev_cbit
pushl $__KERNEL_CS pushl $__KERNEL_CS
pushl %eax pushl %eax
...@@ -694,6 +718,19 @@ SYM_DATA_START(boot_idt) ...@@ -694,6 +718,19 @@ SYM_DATA_START(boot_idt)
.endr .endr
SYM_DATA_END_LABEL(boot_idt, SYM_L_GLOBAL, boot_idt_end) SYM_DATA_END_LABEL(boot_idt, SYM_L_GLOBAL, boot_idt_end)
#ifdef CONFIG_AMD_MEM_ENCRYPT
SYM_DATA_START(boot32_idt_desc)
.word boot32_idt_end - boot32_idt - 1
.long 0
SYM_DATA_END(boot32_idt_desc)
.balign 8
SYM_DATA_START(boot32_idt)
.rept 32
.quad 0
.endr
SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLOBAL, boot32_idt_end)
#endif
#ifdef CONFIG_EFI_STUB #ifdef CONFIG_EFI_STUB
SYM_DATA(image_offset, .long 0) SYM_DATA(image_offset, .long 0)
#endif #endif
...@@ -786,6 +823,137 @@ SYM_DATA_START_LOCAL(loaded_image_proto) ...@@ -786,6 +823,137 @@ SYM_DATA_START_LOCAL(loaded_image_proto)
SYM_DATA_END(loaded_image_proto) SYM_DATA_END(loaded_image_proto)
#endif #endif
#ifdef CONFIG_AMD_MEM_ENCRYPT
__HEAD
.code32
/*
* Write an IDT entry into boot32_idt
*
* Parameters:
*
* %eax: Handler address
* %edx: Vector number
*
* Physical offset is expected in %ebp
*/
SYM_FUNC_START(startup32_set_idt_entry)
push %ebx
push %ecx
/* IDT entry address to %ebx */
leal rva(boot32_idt)(%ebp), %ebx
shl $3, %edx
addl %edx, %ebx
/* Build IDT entry, lower 4 bytes */
movl %eax, %edx
andl $0x0000ffff, %edx # Target code segment offset [15:0]
movl $__KERNEL32_CS, %ecx # Target code segment selector
shl $16, %ecx
orl %ecx, %edx
/* Store lower 4 bytes to IDT */
movl %edx, (%ebx)
/* Build IDT entry, upper 4 bytes */
movl %eax, %edx
andl $0xffff0000, %edx # Target code segment offset [31:16]
orl $0x00008e00, %edx # Present, Type 32-bit Interrupt Gate
/* Store upper 4 bytes to IDT */
movl %edx, 4(%ebx)
pop %ecx
pop %ebx
ret
SYM_FUNC_END(startup32_set_idt_entry)
#endif
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)
lidt rva(boot32_idt_desc)(%ebp)
#endif
ret
SYM_FUNC_END(startup32_load_idt)
/*
* Check for the correct C-bit position when the startup_32 boot-path is used.
*
* The check makes use of the fact that all memory is encrypted when paging is
* disabled. The function creates 64 bits of random data using the RDRAND
* instruction. RDRAND is mandatory for SEV guests, so always available. If the
* hypervisor violates that the kernel will crash right here.
*
* The 64 bits of random data are stored to a memory location and at the same
* time kept in the %eax and %ebx registers. Since encryption is always active
* when paging is off the random data will be stored encrypted in main memory.
*
* Then paging is enabled. When the C-bit position is correct all memory is
* still mapped encrypted and comparing the register values with memory will
* succeed. An incorrect C-bit position will map all memory unencrypted, so that
* the compare will use the encrypted random data and fail.
*/
SYM_FUNC_START(startup32_check_sev_cbit)
#ifdef CONFIG_AMD_MEM_ENCRYPT
pushl %eax
pushl %ebx
pushl %ecx
pushl %edx
/* Check for non-zero sev_status */
movl rva(sev_status)(%ebp), %eax
testl %eax, %eax
jz 4f
/*
* Get two 32-bit random values - Don't bail out if RDRAND fails
* because it is better to prevent forward progress if no random value
* can be gathered.
*/
1: rdrand %eax
jnc 1b
2: rdrand %ebx
jnc 2b
/* Store to memory and keep it in the registers */
movl %eax, rva(sev_check_data)(%ebp)
movl %ebx, rva(sev_check_data+4)(%ebp)
/* Enable paging to see if encryption is active */
movl %cr0, %edx /* Backup %cr0 in %edx */
movl $(X86_CR0_PG | X86_CR0_PE), %ecx /* Enable Paging and Protected mode */
movl %ecx, %cr0
cmpl %eax, rva(sev_check_data)(%ebp)
jne 3f
cmpl %ebx, rva(sev_check_data+4)(%ebp)
jne 3f
movl %edx, %cr0 /* Restore previous %cr0 */
jmp 4f
3: /* Check failed - hlt the machine */
hlt
jmp 3b
4:
popl %edx
popl %ecx
popl %ebx
popl %eax
#endif
ret
SYM_FUNC_END(startup32_check_sev_cbit)
/* /*
* Stack and heap for uncompression * Stack and heap for uncompression
*/ */
......
...@@ -52,3 +52,17 @@ void load_stage2_idt(void) ...@@ -52,3 +52,17 @@ void load_stage2_idt(void)
load_boot_idt(&boot_idt_desc); load_boot_idt(&boot_idt_desc);
} }
void cleanup_exception_handling(void)
{
/*
* Flush GHCB from cache and map it encrypted again when running as
* SEV-ES guest.
*/
sev_es_shutdown_ghcb();
/* Set a null-idt, disabling #PF and #VC handling */
boot_idt_desc.size = 0;
boot_idt_desc.address = 0;
load_boot_idt(&boot_idt_desc);
}
...@@ -23,12 +23,6 @@ SYM_FUNC_START(get_sev_encryption_bit) ...@@ -23,12 +23,6 @@ SYM_FUNC_START(get_sev_encryption_bit)
push %ecx push %ecx
push %edx push %edx
/* 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 */ movl $0x80000000, %eax /* CPUID to check the highest leaf */
cpuid cpuid
cmpl $0x8000001f, %eax /* See if 0x8000001f is available */ cmpl $0x8000001f, %eax /* See if 0x8000001f is available */
...@@ -67,10 +61,132 @@ SYM_FUNC_START(get_sev_encryption_bit) ...@@ -67,10 +61,132 @@ SYM_FUNC_START(get_sev_encryption_bit)
ret ret
SYM_FUNC_END(get_sev_encryption_bit) 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 .code64
#include "../../kernel/sev_verify_cbit.S" #include "../../kernel/sev_verify_cbit.S"
SYM_FUNC_START(set_sev_encryption_mask) SYM_FUNC_START(set_sev_encryption_mask)
#ifdef CONFIG_AMD_MEM_ENCRYPT #ifdef CONFIG_AMD_MEM_ENCRYPT
push %rbp push %rbp
......
...@@ -443,11 +443,8 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, ...@@ -443,11 +443,8 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
handle_relocations(output, output_len, virt_addr); handle_relocations(output, output_len, virt_addr);
debug_putstr("done.\nBooting the kernel.\n"); debug_putstr("done.\nBooting the kernel.\n");
/* /* Disable exception handling before booting the kernel */
* Flush GHCB from cache and map it encrypted again when running as cleanup_exception_handling();
* SEV-ES guest.
*/
sev_es_shutdown_ghcb();
return output; return output;
} }
......
...@@ -155,6 +155,12 @@ extern pteval_t __default_kernel_pte_mask; ...@@ -155,6 +155,12 @@ extern pteval_t __default_kernel_pte_mask;
extern gate_desc boot_idt[BOOT_IDT_ENTRIES]; extern gate_desc boot_idt[BOOT_IDT_ENTRIES];
extern struct desc_ptr boot_idt_desc; extern struct desc_ptr boot_idt_desc;
#ifdef CONFIG_X86_64
void cleanup_exception_handling(void);
#else
static inline void cleanup_exception_handling(void) { }
#endif
/* IDT Entry Points */ /* IDT Entry Points */
void boot_page_fault(void); void boot_page_fault(void);
void boot_stage1_vc(void); void boot_stage1_vc(void);
......
...@@ -200,14 +200,8 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code) ...@@ -200,14 +200,8 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
} }
finish: finish:
if (result == ES_OK) { if (result == ES_OK)
vc_finish_insn(&ctxt); vc_finish_insn(&ctxt);
} else if (result != ES_RETRY) { else if (result != ES_RETRY)
/* sev_es_terminate(GHCB_SEV_ES_REASON_GENERAL_REQUEST);
* For now, just halt the machine. That makes debugging easier,
* later we just call sev_es_terminate() here.
*/
while (true)
asm volatile("hlt\n");
}
} }
...@@ -24,7 +24,7 @@ static bool __init sev_es_check_cpu_features(void) ...@@ -24,7 +24,7 @@ static bool __init sev_es_check_cpu_features(void)
return true; return true;
} }
static void sev_es_terminate(unsigned int reason) static void __noreturn sev_es_terminate(unsigned int reason)
{ {
u64 val = GHCB_SEV_TERMINATE; u64 val = GHCB_SEV_TERMINATE;
...@@ -186,7 +186,6 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) ...@@ -186,7 +186,6 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
* make it accessible to the hypervisor. * make it accessible to the hypervisor.
* *
* In particular, check for: * In particular, check for:
* - Hypervisor CPUID bit
* - Availability of CPUID leaf 0x8000001f * - Availability of CPUID leaf 0x8000001f
* - SEV CPUID bit. * - SEV CPUID bit.
* *
...@@ -194,10 +193,7 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) ...@@ -194,10 +193,7 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
* can't be checked here. * can't be checked here.
*/ */
if ((fn == 1 && !(regs->cx & BIT(31)))) if (fn == 0x80000000 && (regs->ax < 0x8000001f))
/* Hypervisor bit */
goto fail;
else if (fn == 0x80000000 && (regs->ax < 0x8000001f))
/* SEV leaf check */ /* SEV leaf check */
goto fail; goto fail;
else if ((fn == 0x8000001f && !(regs->ax & BIT(1)))) else if ((fn == 0x8000001f && !(regs->ax & BIT(1))))
...@@ -210,12 +206,8 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) ...@@ -210,12 +206,8 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
return; return;
fail: fail:
sev_es_wr_ghcb_msr(GHCB_SEV_TERMINATE); /* Terminate the guest */
VMGEXIT(); sev_es_terminate(GHCB_SEV_ES_REASON_GENERAL_REQUEST);
/* Shouldn't get here - if we do halt the machine */
while (true)
asm volatile("hlt\n");
} }
static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt, static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt,
......
...@@ -137,29 +137,41 @@ static __always_inline bool on_vc_stack(struct pt_regs *regs) ...@@ -137,29 +137,41 @@ static __always_inline bool on_vc_stack(struct pt_regs *regs)
} }
/* /*
* This function handles the case when an NMI is raised in the #VC exception * This function handles the case when an NMI is raised in the #VC
* handler entry code. In this case, the IST entry for #VC must be adjusted, so * exception handler entry code, before the #VC handler has switched off
* that any subsequent #VC exception will not overwrite the stack contents of the * its IST stack. In this case, the IST entry for #VC must be adjusted,
* interrupted #VC handler. * so that any nested #VC exception will not overwrite the stack
* contents of the interrupted #VC handler.
* *
* The IST entry is adjusted unconditionally so that it can be also be * The IST entry is adjusted unconditionally so that it can be also be
* unconditionally adjusted back in sev_es_ist_exit(). Otherwise a nested * unconditionally adjusted back in __sev_es_ist_exit(). Otherwise a
* sev_es_ist_exit() call may adjust back the IST entry too early. * nested sev_es_ist_exit() call may adjust back the IST entry too
* early.
*
* The __sev_es_ist_enter() and __sev_es_ist_exit() functions always run
* on the NMI IST stack, as they are only called from NMI handling code
* right now.
*/ */
void noinstr __sev_es_ist_enter(struct pt_regs *regs) void noinstr __sev_es_ist_enter(struct pt_regs *regs)
{ {
unsigned long old_ist, new_ist; unsigned long old_ist, new_ist;
/* Read old IST entry */ /* Read old IST entry */
old_ist = __this_cpu_read(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC]); new_ist = old_ist = __this_cpu_read(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC]);
/* Make room on the IST stack */ /*
* If NMI happened while on the #VC IST stack, set the new IST
* value below regs->sp, so that the interrupted stack frame is
* not overwritten by subsequent #VC exceptions.
*/
if (on_vc_stack(regs)) if (on_vc_stack(regs))
new_ist = ALIGN_DOWN(regs->sp, 8) - sizeof(old_ist); new_ist = regs->sp;
else
new_ist = old_ist - sizeof(old_ist);
/* Store old IST entry */ /*
* Reserve additional 8 bytes and store old IST value so this
* adjustment can be unrolled in __sev_es_ist_exit().
*/
new_ist -= sizeof(old_ist);
*(unsigned long *)new_ist = old_ist; *(unsigned long *)new_ist = old_ist;
/* Set new IST entry */ /* Set new IST entry */
...@@ -277,7 +289,7 @@ static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt) ...@@ -277,7 +289,7 @@ static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
return ES_EXCEPTION; return ES_EXCEPTION;
} }
insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE - res, 1); insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE, 1);
insn_get_length(&ctxt->insn); insn_get_length(&ctxt->insn);
} }
......
...@@ -19,6 +19,7 @@ ...@@ -19,6 +19,7 @@
#include <linux/kernel.h> #include <linux/kernel.h>
#include <linux/bitops.h> #include <linux/bitops.h>
#include <linux/dma-mapping.h> #include <linux/dma-mapping.h>
#include <linux/virtio_config.h>
#include <asm/tlbflush.h> #include <asm/tlbflush.h>
#include <asm/fixmap.h> #include <asm/fixmap.h>
...@@ -484,3 +485,8 @@ void __init mem_encrypt_init(void) ...@@ -484,3 +485,8 @@ void __init mem_encrypt_init(void)
print_mem_encrypt_feature_info(); print_mem_encrypt_feature_info();
} }
int arch_has_restricted_virtio_memory_access(void)
{
return sev_active();
}
EXPORT_SYMBOL_GPL(arch_has_restricted_virtio_memory_access);
...@@ -503,14 +503,10 @@ void __init sme_enable(struct boot_params *bp) ...@@ -503,14 +503,10 @@ void __init sme_enable(struct boot_params *bp)
#define AMD_SME_BIT BIT(0) #define AMD_SME_BIT BIT(0)
#define AMD_SEV_BIT BIT(1) #define AMD_SEV_BIT BIT(1)
/*
* Set the feature mask (SME or SEV) based on whether we are /* Check the SEV MSR whether SEV or SME is enabled */
* running under a hypervisor. sev_status = __rdmsr(MSR_AMD64_SEV);
*/ feature_mask = (sev_status & MSR_AMD64_SEV_ENABLED) ? AMD_SEV_BIT : AMD_SME_BIT;
eax = 1;
ecx = 0;
native_cpuid(&eax, &ebx, &ecx, &edx);
feature_mask = (ecx & BIT(31)) ? AMD_SEV_BIT : AMD_SME_BIT;
/* /*
* Check for the SME/SEV feature: * Check for the SME/SEV feature:
...@@ -530,19 +526,26 @@ void __init sme_enable(struct boot_params *bp) ...@@ -530,19 +526,26 @@ void __init sme_enable(struct boot_params *bp)
/* Check if memory encryption is enabled */ /* Check if memory encryption is enabled */
if (feature_mask == AMD_SME_BIT) { if (feature_mask == AMD_SME_BIT) {
/*
* No SME if Hypervisor bit is set. This check is here to
* prevent a guest from trying to enable SME. For running as a
* KVM guest the MSR_K8_SYSCFG will be sufficient, but there
* might be other hypervisors which emulate that MSR as non-zero
* or even pass it through to the guest.
* A malicious hypervisor can still trick a guest into this
* path, but there is no way to protect against that.
*/
eax = 1;
ecx = 0;
native_cpuid(&eax, &ebx, &ecx, &edx);
if (ecx & BIT(31))
return;
/* For SME, check the SYSCFG MSR */ /* For SME, check the SYSCFG MSR */
msr = __rdmsr(MSR_K8_SYSCFG); msr = __rdmsr(MSR_K8_SYSCFG);
if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT)) if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT))
return; return;
} else { } else {
/* For SEV, check the SEV MSR */
msr = __rdmsr(MSR_AMD64_SEV);
if (!(msr & MSR_AMD64_SEV_ENABLED))
return;
/* Save SEV_STATUS to avoid reading MSR again */
sev_status = msr;
/* SEV state cannot be controlled by a command line option */ /* SEV state cannot be controlled by a command line option */
sme_me_mask = me_mask; sme_me_mask = me_mask;
sev_enabled = true; sev_enabled = true;
......
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