Commit 1cd9c22f authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Ingo Molnar
Browse files

x86/mm/encrypt: Move page table helpers into separate translation unit 



There are bunch of functions in mem_encrypt.c that operate on the
identity mapping, which means they want virtual addresses to be equal to
physical one, without PAGE_OFFSET shift.

We also need to avoid paravirtualizaion call there.

Getting this done is tricky. We cannot use usual page table helpers.
It forces us to open-code a lot of things. It makes code ugly and hard
to modify.

We can get it work with the page table helpers, but it requires few
preprocessor tricks. These tricks may have side effects for the rest of
the file.

Let's isolate such functions into own translation unit.

Tested-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180131135404.40692-2-kirill.shutemov@linux.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 515ab7c4

arch/x86/include/asm/mem_encrypt.h

+1 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#ifdef CONFIG_AMD_MEM_ENCRYPT



extern u64 sme_me_mask;

extern bool sev_enabled;



void sme_encrypt_execute(unsigned long encrypted_kernel_vaddr,

			 unsigned long decrypted_kernel_vaddr,

arch/x86/mm/Makefile

+9 −5
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0

# Kernel does not boot with instrumentation of tlb.c and mem_encrypt.c

# Kernel does not boot with instrumentation of tlb.c and mem_encrypt*.c

KCOV_INSTRUMENT_tlb.o			:= n

KCOV_INSTRUMENT_mem_encrypt.o		:= n

KCOV_INSTRUMENT_mem_encrypt_identity.o	:= n



KASAN_SANITIZE_mem_encrypt.o		:= n

KASAN_SANITIZE_mem_encrypt_identity.o	:= n



ifdef CONFIG_FUNCTION_TRACER

CFLAGS_REMOVE_mem_encrypt.o		= -pg

CFLAGS_REMOVE_mem_encrypt_identity.o	= -pg

endif



obj-y	:=  init.o init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \
@@ -47,4 +50,5 @@ obj-$(CONFIG_RANDOMIZE_MEMORY) += kaslr.o 
obj-$(CONFIG_PAGE_TABLE_ISOLATION)		+= pti.o



obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt.o

obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_identity.o

obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_boot.o

arch/x86/mm/mem_encrypt.c

+1 −577
Original line number Diff line number Diff line
@@ -25,17 +25,12 @@ 
#include <asm/bootparam.h>

#include <asm/set_memory.h>

#include <asm/cacheflush.h>

#include <asm/sections.h>

#include <asm/processor-flags.h>

#include <asm/msr.h>

#include <asm/cmdline.h>



#include "mm_internal.h"



static char sme_cmdline_arg[] __initdata = "mem_encrypt";

static char sme_cmdline_on[]  __initdata = "on";

static char sme_cmdline_off[] __initdata = "off";



/*

 * Since SME related variables are set early in the boot process they must

 * reside in the .data section so as not to be zeroed out when the .bss
@@ -46,7 +41,7 @@ EXPORT_SYMBOL(sme_me_mask); 
DEFINE_STATIC_KEY_FALSE(sev_enable_key);

EXPORT_SYMBOL_GPL(sev_enable_key);



static bool sev_enabled __section(.data);

bool sev_enabled __section(.data);



/* Buffer used for early in-place encryption by BSP, no locking needed */

static char sme_early_buffer[PAGE_SIZE] __aligned(PAGE_SIZE);
@@ -463,574 +458,3 @@ void swiotlb_set_mem_attributes(void *vaddr, unsigned long size) 
	/* Make the SWIOTLB buffer area decrypted */

	set_memory_decrypted((unsigned long)vaddr, size >> PAGE_SHIFT);

}
 


struct sme_populate_pgd_data {

	void	*pgtable_area;

	pgd_t	*pgd;



	pmdval_t pmd_flags;

	pteval_t pte_flags;

	unsigned long paddr;



	unsigned long vaddr;

	unsigned long vaddr_end;

};



static void __init sme_clear_pgd(struct sme_populate_pgd_data *ppd)

{

	unsigned long pgd_start, pgd_end, pgd_size;

	pgd_t *pgd_p;



	pgd_start = ppd->vaddr & PGDIR_MASK;

	pgd_end = ppd->vaddr_end & PGDIR_MASK;



	pgd_size = (((pgd_end - pgd_start) / PGDIR_SIZE) + 1) * sizeof(pgd_t);



	pgd_p = ppd->pgd + pgd_index(ppd->vaddr);



	memset(pgd_p, 0, pgd_size);

}



#define PGD_FLAGS		_KERNPG_TABLE_NOENC

#define P4D_FLAGS		_KERNPG_TABLE_NOENC

#define PUD_FLAGS		_KERNPG_TABLE_NOENC

#define PMD_FLAGS		_KERNPG_TABLE_NOENC



#define PMD_FLAGS_LARGE		(__PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL)



#define PMD_FLAGS_DEC		PMD_FLAGS_LARGE

#define PMD_FLAGS_DEC_WP	((PMD_FLAGS_DEC & ~_PAGE_CACHE_MASK) | \

				 (_PAGE_PAT | _PAGE_PWT))



#define PMD_FLAGS_ENC		(PMD_FLAGS_LARGE | _PAGE_ENC)



#define PTE_FLAGS		(__PAGE_KERNEL_EXEC & ~_PAGE_GLOBAL)



#define PTE_FLAGS_DEC		PTE_FLAGS

#define PTE_FLAGS_DEC_WP	((PTE_FLAGS_DEC & ~_PAGE_CACHE_MASK) | \

				 (_PAGE_PAT | _PAGE_PWT))



#define PTE_FLAGS_ENC		(PTE_FLAGS | _PAGE_ENC)



static pmd_t __init *sme_prepare_pgd(struct sme_populate_pgd_data *ppd)

{

	pgd_t *pgd_p;

	p4d_t *p4d_p;

	pud_t *pud_p;

	pmd_t *pmd_p;



	pgd_p = ppd->pgd + pgd_index(ppd->vaddr);

	if (native_pgd_val(*pgd_p)) {

		if (IS_ENABLED(CONFIG_X86_5LEVEL))

			p4d_p = (p4d_t *)(native_pgd_val(*pgd_p) & ~PTE_FLAGS_MASK);

		else

			pud_p = (pud_t *)(native_pgd_val(*pgd_p) & ~PTE_FLAGS_MASK);

	} else {

		pgd_t pgd;



		if (IS_ENABLED(CONFIG_X86_5LEVEL)) {

			p4d_p = ppd->pgtable_area;

			memset(p4d_p, 0, sizeof(*p4d_p) * PTRS_PER_P4D);

			ppd->pgtable_area += sizeof(*p4d_p) * PTRS_PER_P4D;



			pgd = native_make_pgd((pgdval_t)p4d_p + PGD_FLAGS);

		} else {

			pud_p = ppd->pgtable_area;

			memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);

			ppd->pgtable_area += sizeof(*pud_p) * PTRS_PER_PUD;



			pgd = native_make_pgd((pgdval_t)pud_p + PGD_FLAGS);

		}

		native_set_pgd(pgd_p, pgd);

	}



	if (IS_ENABLED(CONFIG_X86_5LEVEL)) {

		p4d_p += p4d_index(ppd->vaddr);

		if (native_p4d_val(*p4d_p)) {

			pud_p = (pud_t *)(native_p4d_val(*p4d_p) & ~PTE_FLAGS_MASK);

		} else {

			p4d_t p4d;



			pud_p = ppd->pgtable_area;

			memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);

			ppd->pgtable_area += sizeof(*pud_p) * PTRS_PER_PUD;



			p4d = native_make_p4d((pudval_t)pud_p + P4D_FLAGS);

			native_set_p4d(p4d_p, p4d);

		}

	}



	pud_p += pud_index(ppd->vaddr);

	if (native_pud_val(*pud_p)) {

		if (native_pud_val(*pud_p) & _PAGE_PSE)

			return NULL;



		pmd_p = (pmd_t *)(native_pud_val(*pud_p) & ~PTE_FLAGS_MASK);

	} else {

		pud_t pud;



		pmd_p = ppd->pgtable_area;

		memset(pmd_p, 0, sizeof(*pmd_p) * PTRS_PER_PMD);

		ppd->pgtable_area += sizeof(*pmd_p) * PTRS_PER_PMD;



		pud = native_make_pud((pmdval_t)pmd_p + PUD_FLAGS);

		native_set_pud(pud_p, pud);

	}



	return pmd_p;

}



static void __init sme_populate_pgd_large(struct sme_populate_pgd_data *ppd)

{

	pmd_t *pmd_p;



	pmd_p = sme_prepare_pgd(ppd);

	if (!pmd_p)

		return;



	pmd_p += pmd_index(ppd->vaddr);

	if (!native_pmd_val(*pmd_p) || !(native_pmd_val(*pmd_p) & _PAGE_PSE))

		native_set_pmd(pmd_p, native_make_pmd(ppd->paddr | ppd->pmd_flags));

}



static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd)

{

	pmd_t *pmd_p;

	pte_t *pte_p;



	pmd_p = sme_prepare_pgd(ppd);

	if (!pmd_p)

		return;



	pmd_p += pmd_index(ppd->vaddr);

	if (native_pmd_val(*pmd_p)) {

		if (native_pmd_val(*pmd_p) & _PAGE_PSE)

			return;



		pte_p = (pte_t *)(native_pmd_val(*pmd_p) & ~PTE_FLAGS_MASK);

	} else {

		pmd_t pmd;



		pte_p = ppd->pgtable_area;

		memset(pte_p, 0, sizeof(*pte_p) * PTRS_PER_PTE);

		ppd->pgtable_area += sizeof(*pte_p) * PTRS_PER_PTE;



		pmd = native_make_pmd((pteval_t)pte_p + PMD_FLAGS);

		native_set_pmd(pmd_p, pmd);

	}



	pte_p += pte_index(ppd->vaddr);

	if (!native_pte_val(*pte_p))

		native_set_pte(pte_p, native_make_pte(ppd->paddr | ppd->pte_flags));

}



static void __init __sme_map_range_pmd(struct sme_populate_pgd_data *ppd)

{

	while (ppd->vaddr < ppd->vaddr_end) {

		sme_populate_pgd_large(ppd);



		ppd->vaddr += PMD_PAGE_SIZE;

		ppd->paddr += PMD_PAGE_SIZE;

	}

}



static void __init __sme_map_range_pte(struct sme_populate_pgd_data *ppd)

{

	while (ppd->vaddr < ppd->vaddr_end) {

		sme_populate_pgd(ppd);



		ppd->vaddr += PAGE_SIZE;

		ppd->paddr += PAGE_SIZE;

	}

}



static void __init __sme_map_range(struct sme_populate_pgd_data *ppd,

				   pmdval_t pmd_flags, pteval_t pte_flags)

{

	unsigned long vaddr_end;



	ppd->pmd_flags = pmd_flags;

	ppd->pte_flags = pte_flags;



	/* Save original end value since we modify the struct value */

	vaddr_end = ppd->vaddr_end;



	/* If start is not 2MB aligned, create PTE entries */

	ppd->vaddr_end = ALIGN(ppd->vaddr, PMD_PAGE_SIZE);

	__sme_map_range_pte(ppd);



	/* Create PMD entries */

	ppd->vaddr_end = vaddr_end & PMD_PAGE_MASK;

	__sme_map_range_pmd(ppd);



	/* If end is not 2MB aligned, create PTE entries */

	ppd->vaddr_end = vaddr_end;

	__sme_map_range_pte(ppd);

}



static void __init sme_map_range_encrypted(struct sme_populate_pgd_data *ppd)

{

	__sme_map_range(ppd, PMD_FLAGS_ENC, PTE_FLAGS_ENC);

}



static void __init sme_map_range_decrypted(struct sme_populate_pgd_data *ppd)

{

	__sme_map_range(ppd, PMD_FLAGS_DEC, PTE_FLAGS_DEC);

}



static void __init sme_map_range_decrypted_wp(struct sme_populate_pgd_data *ppd)

{

	__sme_map_range(ppd, PMD_FLAGS_DEC_WP, PTE_FLAGS_DEC_WP);

}



static unsigned long __init sme_pgtable_calc(unsigned long len)

{

	unsigned long p4d_size, pud_size, pmd_size, pte_size;

	unsigned long total;



	/*

	 * Perform a relatively simplistic calculation of the pagetable

	 * entries that are needed. Those mappings will be covered mostly

	 * by 2MB PMD entries so we can conservatively calculate the required

	 * number of P4D, PUD and PMD structures needed to perform the

	 * mappings.  For mappings that are not 2MB aligned, PTE mappings

	 * would be needed for the start and end portion of the address range

	 * that fall outside of the 2MB alignment.  This results in, at most,

	 * two extra pages to hold PTE entries for each range that is mapped.

	 * Incrementing the count for each covers the case where the addresses

	 * cross entries.

	 */

	if (IS_ENABLED(CONFIG_X86_5LEVEL)) {

		p4d_size = (ALIGN(len, PGDIR_SIZE) / PGDIR_SIZE) + 1;

		p4d_size *= sizeof(p4d_t) * PTRS_PER_P4D;

		pud_size = (ALIGN(len, P4D_SIZE) / P4D_SIZE) + 1;

		pud_size *= sizeof(pud_t) * PTRS_PER_PUD;

	} else {

		p4d_size = 0;

		pud_size = (ALIGN(len, PGDIR_SIZE) / PGDIR_SIZE) + 1;

		pud_size *= sizeof(pud_t) * PTRS_PER_PUD;

	}

	pmd_size = (ALIGN(len, PUD_SIZE) / PUD_SIZE) + 1;

	pmd_size *= sizeof(pmd_t) * PTRS_PER_PMD;

	pte_size = 2 * sizeof(pte_t) * PTRS_PER_PTE;



	total = p4d_size + pud_size + pmd_size + pte_size;



	/*

	 * Now calculate the added pagetable structures needed to populate

	 * the new pagetables.

	 */

	if (IS_ENABLED(CONFIG_X86_5LEVEL)) {

		p4d_size = ALIGN(total, PGDIR_SIZE) / PGDIR_SIZE;

		p4d_size *= sizeof(p4d_t) * PTRS_PER_P4D;

		pud_size = ALIGN(total, P4D_SIZE) / P4D_SIZE;

		pud_size *= sizeof(pud_t) * PTRS_PER_PUD;

	} else {

		p4d_size = 0;

		pud_size = ALIGN(total, PGDIR_SIZE) / PGDIR_SIZE;

		pud_size *= sizeof(pud_t) * PTRS_PER_PUD;

	}

	pmd_size = ALIGN(total, PUD_SIZE) / PUD_SIZE;

	pmd_size *= sizeof(pmd_t) * PTRS_PER_PMD;



	total += p4d_size + pud_size + pmd_size;



	return total;

}



void __init __nostackprotector sme_encrypt_kernel(struct boot_params *bp)

{

	unsigned long workarea_start, workarea_end, workarea_len;

	unsigned long execute_start, execute_end, execute_len;

	unsigned long kernel_start, kernel_end, kernel_len;

	unsigned long initrd_start, initrd_end, initrd_len;

	struct sme_populate_pgd_data ppd;

	unsigned long pgtable_area_len;

	unsigned long decrypted_base;



	if (!sme_active())

		return;



	/*

	 * Prepare for encrypting the kernel and initrd by building new

	 * pagetables with the necessary attributes needed to encrypt the

	 * kernel in place.

	 *

	 *   One range of virtual addresses will map the memory occupied

	 *   by the kernel and initrd as encrypted.

	 *

	 *   Another range of virtual addresses will map the memory occupied

	 *   by the kernel and initrd as decrypted and write-protected.

	 *

	 *     The use of write-protect attribute will prevent any of the

	 *     memory from being cached.

	 */



	/* Physical addresses gives us the identity mapped virtual addresses */

	kernel_start = __pa_symbol(_text);

	kernel_end = ALIGN(__pa_symbol(_end), PMD_PAGE_SIZE);

	kernel_len = kernel_end - kernel_start;



	initrd_start = 0;

	initrd_end = 0;

	initrd_len = 0;

#ifdef CONFIG_BLK_DEV_INITRD

	initrd_len = (unsigned long)bp->hdr.ramdisk_size |

		     ((unsigned long)bp->ext_ramdisk_size << 32);

	if (initrd_len) {

		initrd_start = (unsigned long)bp->hdr.ramdisk_image |

			       ((unsigned long)bp->ext_ramdisk_image << 32);

		initrd_end = PAGE_ALIGN(initrd_start + initrd_len);

		initrd_len = initrd_end - initrd_start;

	}

#endif



	/* Set the encryption workarea to be immediately after the kernel */

	workarea_start = kernel_end;



	/*

	 * Calculate required number of workarea bytes needed:

	 *   executable encryption area size:

	 *     stack page (PAGE_SIZE)

	 *     encryption routine page (PAGE_SIZE)

	 *     intermediate copy buffer (PMD_PAGE_SIZE)

	 *   pagetable structures for the encryption of the kernel

	 *   pagetable structures for workarea (in case not currently mapped)

	 */

	execute_start = workarea_start;

	execute_end = execute_start + (PAGE_SIZE * 2) + PMD_PAGE_SIZE;

	execute_len = execute_end - execute_start;



	/*

	 * One PGD for both encrypted and decrypted mappings and a set of

	 * PUDs and PMDs for each of the encrypted and decrypted mappings.

	 */

	pgtable_area_len = sizeof(pgd_t) * PTRS_PER_PGD;

	pgtable_area_len += sme_pgtable_calc(execute_end - kernel_start) * 2;

	if (initrd_len)

		pgtable_area_len += sme_pgtable_calc(initrd_len) * 2;



	/* PUDs and PMDs needed in the current pagetables for the workarea */

	pgtable_area_len += sme_pgtable_calc(execute_len + pgtable_area_len);



	/*

	 * The total workarea includes the executable encryption area and

	 * the pagetable area. The start of the workarea is already 2MB

	 * aligned, align the end of the workarea on a 2MB boundary so that

	 * we don't try to create/allocate PTE entries from the workarea

	 * before it is mapped.

	 */

	workarea_len = execute_len + pgtable_area_len;

	workarea_end = ALIGN(workarea_start + workarea_len, PMD_PAGE_SIZE);



	/*

	 * Set the address to the start of where newly created pagetable

	 * structures (PGDs, PUDs and PMDs) will be allocated. New pagetable

	 * structures are created when the workarea is added to the current

	 * pagetables and when the new encrypted and decrypted kernel

	 * mappings are populated.

	 */

	ppd.pgtable_area = (void *)execute_end;



	/*

	 * Make sure the current pagetable structure has entries for

	 * addressing the workarea.

	 */

	ppd.pgd = (pgd_t *)native_read_cr3_pa();

	ppd.paddr = workarea_start;

	ppd.vaddr = workarea_start;

	ppd.vaddr_end = workarea_end;

	sme_map_range_decrypted(&ppd);



	/* Flush the TLB - no globals so cr3 is enough */

	native_write_cr3(__native_read_cr3());



	/*

	 * A new pagetable structure is being built to allow for the kernel

	 * and initrd to be encrypted. It starts with an empty PGD that will

	 * then be populated with new PUDs and PMDs as the encrypted and

	 * decrypted kernel mappings are created.

	 */

	ppd.pgd = ppd.pgtable_area;

	memset(ppd.pgd, 0, sizeof(pgd_t) * PTRS_PER_PGD);

	ppd.pgtable_area += sizeof(pgd_t) * PTRS_PER_PGD;



	/*

	 * A different PGD index/entry must be used to get different

	 * pagetable entries for the decrypted mapping. Choose the next

	 * PGD index and convert it to a virtual address to be used as

	 * the base of the mapping.

	 */

	decrypted_base = (pgd_index(workarea_end) + 1) & (PTRS_PER_PGD - 1);

	if (initrd_len) {

		unsigned long check_base;



		check_base = (pgd_index(initrd_end) + 1) & (PTRS_PER_PGD - 1);

		decrypted_base = max(decrypted_base, check_base);

	}

	decrypted_base <<= PGDIR_SHIFT;



	/* Add encrypted kernel (identity) mappings */

	ppd.paddr = kernel_start;

	ppd.vaddr = kernel_start;

	ppd.vaddr_end = kernel_end;

	sme_map_range_encrypted(&ppd);



	/* Add decrypted, write-protected kernel (non-identity) mappings */

	ppd.paddr = kernel_start;

	ppd.vaddr = kernel_start + decrypted_base;

	ppd.vaddr_end = kernel_end + decrypted_base;

	sme_map_range_decrypted_wp(&ppd);



	if (initrd_len) {

		/* Add encrypted initrd (identity) mappings */

		ppd.paddr = initrd_start;

		ppd.vaddr = initrd_start;

		ppd.vaddr_end = initrd_end;

		sme_map_range_encrypted(&ppd);

		/*

		 * Add decrypted, write-protected initrd (non-identity) mappings

		 */

		ppd.paddr = initrd_start;

		ppd.vaddr = initrd_start + decrypted_base;

		ppd.vaddr_end = initrd_end + decrypted_base;

		sme_map_range_decrypted_wp(&ppd);

	}



	/* Add decrypted workarea mappings to both kernel mappings */

	ppd.paddr = workarea_start;

	ppd.vaddr = workarea_start;

	ppd.vaddr_end = workarea_end;

	sme_map_range_decrypted(&ppd);



	ppd.paddr = workarea_start;

	ppd.vaddr = workarea_start + decrypted_base;

	ppd.vaddr_end = workarea_end + decrypted_base;

	sme_map_range_decrypted(&ppd);



	/* Perform the encryption */

	sme_encrypt_execute(kernel_start, kernel_start + decrypted_base,

			    kernel_len, workarea_start, (unsigned long)ppd.pgd);



	if (initrd_len)

		sme_encrypt_execute(initrd_start, initrd_start + decrypted_base,

				    initrd_len, workarea_start,

				    (unsigned long)ppd.pgd);



	/*

	 * At this point we are running encrypted.  Remove the mappings for

	 * the decrypted areas - all that is needed for this is to remove

	 * the PGD entry/entries.

	 */

	ppd.vaddr = kernel_start + decrypted_base;

	ppd.vaddr_end = kernel_end + decrypted_base;

	sme_clear_pgd(&ppd);



	if (initrd_len) {

		ppd.vaddr = initrd_start + decrypted_base;

		ppd.vaddr_end = initrd_end + decrypted_base;

		sme_clear_pgd(&ppd);

	}



	ppd.vaddr = workarea_start + decrypted_base;

	ppd.vaddr_end = workarea_end + decrypted_base;

	sme_clear_pgd(&ppd);



	/* Flush the TLB - no globals so cr3 is enough */

	native_write_cr3(__native_read_cr3());

}



void __init __nostackprotector sme_enable(struct boot_params *bp)

{

	const char *cmdline_ptr, *cmdline_arg, *cmdline_on, *cmdline_off;

	unsigned int eax, ebx, ecx, edx;

	unsigned long feature_mask;

	bool active_by_default;

	unsigned long me_mask;

	char buffer[16];

	u64 msr;



	/* Check for the SME/SEV support leaf */

	eax = 0x80000000;

	ecx = 0;

	native_cpuid(&eax, &ebx, &ecx, &edx);

	if (eax < 0x8000001f)

		return;



#define AMD_SME_BIT	BIT(0)

#define AMD_SEV_BIT	BIT(1)

	/*

	 * Set the feature mask (SME or SEV) based on whether we are

	 * running under a hypervisor.

	 */

	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:

	 *   CPUID Fn8000_001F[EAX]

	 *   - Bit 0 - Secure Memory Encryption support

	 *   - Bit 1 - Secure Encrypted Virtualization support

	 *   CPUID Fn8000_001F[EBX]

	 *   - Bits 5:0 - Pagetable bit position used to indicate encryption

	 */

	eax = 0x8000001f;

	ecx = 0;

	native_cpuid(&eax, &ebx, &ecx, &edx);

	if (!(eax & feature_mask))

		return;



	me_mask = 1UL << (ebx & 0x3f);



	/* Check if memory encryption is enabled */

	if (feature_mask == AMD_SME_BIT) {

		/* For SME, check the SYSCFG MSR */

		msr = __rdmsr(MSR_K8_SYSCFG);

		if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT))

			return;

	} else {

		/* For SEV, check the SEV MSR */

		msr = __rdmsr(MSR_AMD64_SEV);

		if (!(msr & MSR_AMD64_SEV_ENABLED))

			return;



		/* SEV state cannot be controlled by a command line option */

		sme_me_mask = me_mask;

		sev_enabled = true;

		return;

	}



	/*

	 * Fixups have not been applied to phys_base yet and we're running

	 * identity mapped, so we must obtain the address to the SME command

	 * line argument data using rip-relative addressing.

	 */

	asm ("lea sme_cmdline_arg(%%rip), %0"

	     : "=r" (cmdline_arg)

	     : "p" (sme_cmdline_arg));

	asm ("lea sme_cmdline_on(%%rip), %0"

	     : "=r" (cmdline_on)

	     : "p" (sme_cmdline_on));

	asm ("lea sme_cmdline_off(%%rip), %0"

	     : "=r" (cmdline_off)

	     : "p" (sme_cmdline_off));



	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT))

		active_by_default = true;

	else

		active_by_default = false;



	cmdline_ptr = (const char *)((u64)bp->hdr.cmd_line_ptr |

				     ((u64)bp->ext_cmd_line_ptr << 32));



	cmdline_find_option(cmdline_ptr, cmdline_arg, buffer, sizeof(buffer));



	if (!strncmp(buffer, cmdline_on, sizeof(buffer)))

		sme_me_mask = me_mask;

	else if (!strncmp(buffer, cmdline_off, sizeof(buffer)))

		sme_me_mask = 0;

	else

		sme_me_mask = active_by_default ? me_mask : 0;

}

arch/x86/mm/mem_encrypt_identity.c

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