arch/x86/mm/mem_encrypt.c

Source file repositories/reference/linux-study-clean/arch/x86/mm/mem_encrypt.c

File Facts

System
Linux kernel
Corpus path
arch/x86/mm/mem_encrypt.c
Extension
.c
Size
3639 bytes
Lines
141
Domain
Architecture Layer
Bucket
arch/x86
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

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");

		/* Secure Nested Paging */
		if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
			pr_cont(" SEV-SNP");

		pr_cont("\n");

		sev_show_status();

		break;
	default:
		pr_cont("Unknown\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();

	snp_secure_tsc_prepare();

	print_mem_encrypt_feature_info();
}

void __init mem_encrypt_setup_arch(void)
{
	phys_addr_t total_mem = memblock_phys_mem_size();
	unsigned long size;

	/*
	 * Do RMP table fixups after the e820 tables have been setup by
	 * e820__memory_setup().
	 */
	if (cc_platform_has(CC_ATTR_HOST_SEV_SNP))
		snp_fixup_e820_tables();

	if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
		return;

	/*
	 * For SEV and TDX, all DMA has to occur via shared/unencrypted pages.
	 * Kernel uses SWIOTLB to make this happen without changing device
	 * drivers. However, depending on the workload being run, the
	 * default 64MB of SWIOTLB may not be enough and SWIOTLB may
	 * run out of buffers for DMA, resulting in I/O errors and/or
	 * performance degradation especially with high I/O workloads.
	 *
	 * Adjust the default size of SWIOTLB using a percentage of guest
	 * memory for SWIOTLB buffers. Also, as the SWIOTLB bounce buffer
	 * memory is allocated from low memory, ensure that the adjusted size
	 * is within the limits of low available memory.
	 *
	 * The percentage of guest memory used here for SWIOTLB buffers
	 * is more of an approximation of the static adjustment which
	 * 64MB for <1G, and ~128M to 256M for 1G-to-4G, i.e., the 6%
	 */
	size = total_mem * 6 / 100;
	size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
	swiotlb_adjust_size(size);

	/* Set restricted memory access for virtio. */
	virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
}

Annotation

Implementation Notes