Commit 20f07a04 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Borislav Petkov
Browse files

x86/sev: Move common memory encryption code to mem_encrypt.c 



SEV and TDX both protect guest memory from host accesses. They both use
guest physical address bits to communicate to the hardware which pages
receive protection or not. SEV and TDX both assume that all I/O (real
devices and virtio) must be performed to pages *without* protection.

To add this support, AMD SEV code forces force_dma_unencrypted() to
decrypt DMA pages when DMA pages were allocated for I/O. It also uses
swiotlb_update_mem_attributes() to update decryption bits in SWIOTLB DMA
buffers.

Since TDX also uses a similar memory sharing design, all the above
mentioned changes can be reused. So move force_dma_unencrypted(),
SWIOTLB update code and virtio changes out of mem_encrypt_amd.c to
mem_encrypt.c.

Introduce a new config option X86_MEM_ENCRYPT that can be selected by
platforms which use x86 memory encryption features (needed in both AMD
SEV and Intel TDX guest platforms).

Since the code is moved from mem_encrypt_amd.c, inherit the same make
flags.

This is preparation for enabling TDX memory encryption support and it
has no functional changes.

Co-developed-by: default avatarKuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: default avatarKuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarAndi Kleen <ak@linux.intel.com>
Reviewed-by: default avatarTony Luck <tony.luck@intel.com>
Reviewed-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Tested-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20211206135505.75045-4-kirill.shutemov@linux.intel.com
parent dbca5e1a

arch/x86/Kconfig

+7 −3
Original line number Diff line number Diff line
@@ -1523,16 +1523,20 @@ config X86_CPA_STATISTICS 
	  helps to determine the effectiveness of preserving large and huge

	  page mappings when mapping protections are changed.



config X86_MEM_ENCRYPT

	select ARCH_HAS_FORCE_DMA_UNENCRYPTED

	select DYNAMIC_PHYSICAL_MASK

	select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS

	def_bool n



config AMD_MEM_ENCRYPT

	bool "AMD Secure Memory Encryption (SME) support"

	depends on X86_64 && CPU_SUP_AMD

	select DMA_COHERENT_POOL

	select DYNAMIC_PHYSICAL_MASK

	select ARCH_USE_MEMREMAP_PROT

	select ARCH_HAS_FORCE_DMA_UNENCRYPTED

	select INSTRUCTION_DECODER

	select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS

	select ARCH_HAS_CC_PLATFORM

	select X86_MEM_ENCRYPT

	help

	  Say yes to enable support for the encryption of system memory.

	  This requires an AMD processor that supports Secure Memory

arch/x86/mm/Makefile

+5 −0
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

KCOV_INSTRUMENT_tlb.o			:= n

KCOV_INSTRUMENT_mem_encrypt.o		:= n

KCOV_INSTRUMENT_mem_encrypt_amd.o	:= n

KCOV_INSTRUMENT_mem_encrypt_identity.o	:= n



KASAN_SANITIZE_mem_encrypt.o		:= n

KASAN_SANITIZE_mem_encrypt_amd.o	:= n

KASAN_SANITIZE_mem_encrypt_identity.o	:= n
@@ -12,6 +14,7 @@ KASAN_SANITIZE_mem_encrypt_identity.o := n 
KCSAN_SANITIZE := n



ifdef CONFIG_FUNCTION_TRACER

CFLAGS_REMOVE_mem_encrypt.o		= -pg

CFLAGS_REMOVE_mem_encrypt_amd.o		= -pg

CFLAGS_REMOVE_mem_encrypt_identity.o	= -pg

endif
@@ -52,6 +55,8 @@ obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS) += pkeys.o 
obj-$(CONFIG_RANDOMIZE_MEMORY)			+= kaslr.o

obj-$(CONFIG_PAGE_TABLE_ISOLATION)		+= pti.o



obj-$(CONFIG_X86_MEM_ENCRYPT)	+= mem_encrypt.o

obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_amd.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

0 → 100644
+84 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only

/*

 * Memory Encryption Support Common Code

 *

 * Copyright (C) 2016 Advanced Micro Devices, Inc.

 *

 * Author: Tom Lendacky <thomas.lendacky@amd.com>

 */



#include <linux/dma-direct.h>

#include <linux/dma-mapping.h>

#include <linux/swiotlb.h>

#include <linux/cc_platform.h>

#include <linux/mem_encrypt.h>

#include <linux/virtio_config.h>



/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */

bool force_dma_unencrypted(struct device *dev)

{

	/*

	 * For SEV, all DMA must be to unencrypted addresses.

	 */

	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))

		return true;



	/*

	 * For SME, all DMA must be to unencrypted addresses if the

	 * device does not support DMA to addresses that include the

	 * encryption mask.

	 */

	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {

		u64 dma_enc_mask = DMA_BIT_MASK(__ffs64(sme_me_mask));

		u64 dma_dev_mask = min_not_zero(dev->coherent_dma_mask,

						dev->bus_dma_limit);



		if (dma_dev_mask <= dma_enc_mask)

			return true;

	}



	return false;

}



static void print_mem_encrypt_feature_info(void)

{

	pr_info("AMD Memory Encryption Features active:");



	/* Secure Memory Encryption */

	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {

		/*

		 * SME is mutually exclusive with any of the SEV

		 * features below.

		 */

		pr_cont(" SME\n");

		return;

	}



	/* Secure Encrypted Virtualization */

	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))

		pr_cont(" SEV");



	/* Encrypted Register State */

	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))

		pr_cont(" SEV-ES");



	pr_cont("\n");

}



/* Architecture __weak replacement functions */

void __init mem_encrypt_init(void)

{

	if (!cc_platform_has(CC_ATTR_MEM_ENCRYPT))

		return;



	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */

	swiotlb_update_mem_attributes();



	print_mem_encrypt_feature_info();

}



int arch_has_restricted_virtio_memory_access(void)

{

	return cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT);

}

EXPORT_SYMBOL_GPL(arch_has_restricted_virtio_memory_access);

arch/x86/mm/mem_encrypt_amd.c

+0 −69
Original line number Diff line number Diff line
@@ -413,32 +413,6 @@ void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, boo 
	notify_range_enc_status_changed(vaddr, npages, enc);

}



/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */

bool force_dma_unencrypted(struct device *dev)

{

	/*

	 * For SEV, all DMA must be to unencrypted addresses.

	 */

	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))

		return true;



	/*

	 * For SME, all DMA must be to unencrypted addresses if the

	 * device does not support DMA to addresses that include the

	 * encryption mask.

	 */

	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {

		u64 dma_enc_mask = DMA_BIT_MASK(__ffs64(sme_me_mask));

		u64 dma_dev_mask = min_not_zero(dev->coherent_dma_mask,

						dev->bus_dma_limit);



		if (dma_dev_mask <= dma_enc_mask)

			return true;

	}



	return false;

}



void __init mem_encrypt_free_decrypted_mem(void)

{

	unsigned long vaddr, vaddr_end, npages;
@@ -462,46 +436,3 @@ void __init mem_encrypt_free_decrypted_mem(void) 


	free_init_pages("unused decrypted", vaddr, vaddr_end);

}
 


static void print_mem_encrypt_feature_info(void)

{

	pr_info("AMD Memory Encryption Features active:");



	/* Secure Memory Encryption */

	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) {

		/*

		 * SME is mutually exclusive with any of the SEV

		 * features below.

		 */

		pr_cont(" SME\n");

		return;

	}



	/* Secure Encrypted Virtualization */

	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))

		pr_cont(" SEV");



	/* Encrypted Register State */

	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))

		pr_cont(" SEV-ES");



	pr_cont("\n");

}



/* Architecture __weak replacement functions */

void __init mem_encrypt_init(void)

{

	if (!sme_me_mask)

		return;



	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */

	swiotlb_update_mem_attributes();



	print_mem_encrypt_feature_info();

}



int arch_has_restricted_virtio_memory_access(void)

{

	return cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT);

}

EXPORT_SYMBOL_GPL(arch_has_restricted_virtio_memory_access);