ASoC: tlv320aic31xx: Reset registers during power up

[mirror_ubuntu-focal-kernel.git] / arch / x86 / mm / mem_encrypt.c

/*
 * AMD Memory Encryption Support
 *
 * Copyright (C) 2016 Advanced Micro Devices, Inc.
 *
 * Author: Tom Lendacky <thomas.lendacky@amd.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#define DISABLE_BRANCH_PROFILING

#include <linux/linkage.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/dma-mapping.h>
#include <linux/swiotlb.h>
#include <linux/mem_encrypt.h>

#include <asm/tlbflush.h>
#include <asm/fixmap.h>
#include <asm/setup.h>
#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
 * section is later cleared.
 */
u64 sme_me_mask __section(.data) = 0;
EXPORT_SYMBOL(sme_me_mask);
DEFINE_STATIC_KEY_FALSE(sev_enable_key);
EXPORT_SYMBOL_GPL(sev_enable_key);

static 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);

/*
 * This routine does not change the underlying encryption setting of the
 * page(s) that map this memory. It assumes that eventually the memory is
 * meant to be accessed as either encrypted or decrypted but the contents
 * are currently not in the desired state.
 *
 * This routine follows the steps outlined in the AMD64 Architecture
 * Programmer's Manual Volume 2, Section 7.10.8 Encrypt-in-Place.
 */
static void __init __sme_early_enc_dec(resource_size_t paddr,
                                       unsigned long size, bool enc)
{
        void *src, *dst;
        size_t len;

        if (!sme_me_mask)
                return;

        wbinvd();

        /*
         * There are limited number of early mapping slots, so map (at most)
         * one page at time.
         */
        while (size) {
                len = min_t(size_t, sizeof(sme_early_buffer), size);

                /*
                 * Create mappings for the current and desired format of
                 * the memory. Use a write-protected mapping for the source.
                 */
                src = enc ? early_memremap_decrypted_wp(paddr, len) :
                            early_memremap_encrypted_wp(paddr, len);

                dst = enc ? early_memremap_encrypted(paddr, len) :
                            early_memremap_decrypted(paddr, len);

                /*
                 * If a mapping can't be obtained to perform the operation,
                 * then eventual access of that area in the desired mode
                 * will cause a crash.
                 */
                BUG_ON(!src || !dst);

                /*
                 * Use a temporary buffer, of cache-line multiple size, to
                 * avoid data corruption as documented in the APM.
                 */
                memcpy(sme_early_buffer, src, len);
                memcpy(dst, sme_early_buffer, len);

                early_memunmap(dst, len);
                early_memunmap(src, len);

                paddr += len;
                size -= len;
        }
}

void __init sme_early_encrypt(resource_size_t paddr, unsigned long size)
{
        __sme_early_enc_dec(paddr, size, true);
}

void __init sme_early_decrypt(resource_size_t paddr, unsigned long size)
{
        __sme_early_enc_dec(paddr, size, false);
}

static void __init __sme_early_map_unmap_mem(void *vaddr, unsigned long size,
                                             bool map)
{
        unsigned long paddr = (unsigned long)vaddr - __PAGE_OFFSET;
        pmdval_t pmd_flags, pmd;

        /* Use early_pmd_flags but remove the encryption mask */
        pmd_flags = __sme_clr(early_pmd_flags);

        do {
                pmd = map ? (paddr & PMD_MASK) + pmd_flags : 0;
                __early_make_pgtable((unsigned long)vaddr, pmd);

                vaddr += PMD_SIZE;
                paddr += PMD_SIZE;
                size = (size <= PMD_SIZE) ? 0 : size - PMD_SIZE;
        } while (size);

        __native_flush_tlb();
}

void __init sme_unmap_bootdata(char *real_mode_data)
{
        struct boot_params *boot_data;
        unsigned long cmdline_paddr;

        if (!sme_active())
                return;

        /* Get the command line address before unmapping the real_mode_data */
        boot_data = (struct boot_params *)real_mode_data;
        cmdline_paddr = boot_data->hdr.cmd_line_ptr | ((u64)boot_data->ext_cmd_line_ptr << 32);

        __sme_early_map_unmap_mem(real_mode_data, sizeof(boot_params), false);

        if (!cmdline_paddr)
                return;

        __sme_early_map_unmap_mem(__va(cmdline_paddr), COMMAND_LINE_SIZE, false);
}

void __init sme_map_bootdata(char *real_mode_data)
{
        struct boot_params *boot_data;
        unsigned long cmdline_paddr;

        if (!sme_active())
                return;

        __sme_early_map_unmap_mem(real_mode_data, sizeof(boot_params), true);

        /* Get the command line address after mapping the real_mode_data */
        boot_data = (struct boot_params *)real_mode_data;
        cmdline_paddr = boot_data->hdr.cmd_line_ptr | ((u64)boot_data->ext_cmd_line_ptr << 32);

        if (!cmdline_paddr)
                return;

        __sme_early_map_unmap_mem(__va(cmdline_paddr), COMMAND_LINE_SIZE, true);
}

void __init sme_early_init(void)
{
        unsigned int i;

        if (!sme_me_mask)
                return;

        early_pmd_flags = __sme_set(early_pmd_flags);

        __supported_pte_mask = __sme_set(__supported_pte_mask);

        /* Update the protection map with memory encryption mask */
        for (i = 0; i < ARRAY_SIZE(protection_map); i++)
                protection_map[i] = pgprot_encrypted(protection_map[i]);

        if (sev_active())
                swiotlb_force = SWIOTLB_FORCE;
}

static void *sev_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
                       gfp_t gfp, unsigned long attrs)
{
        unsigned long dma_mask;
        unsigned int order;
        struct page *page;
        void *vaddr = NULL;

        dma_mask = dma_alloc_coherent_mask(dev, gfp);
        order = get_order(size);

        /*
         * Memory will be memset to zero after marking decrypted, so don't
         * bother clearing it before.
         */
        gfp &= ~__GFP_ZERO;

        page = alloc_pages_node(dev_to_node(dev), gfp, order);
        if (page) {
                dma_addr_t addr;

                /*
                 * Since we will be clearing the encryption bit, check the
                 * mask with it already cleared.
                 */
                addr = __sme_clr(phys_to_dma(dev, page_to_phys(page)));
                if ((addr + size) > dma_mask) {
                        __free_pages(page, get_order(size));
                } else {
                        vaddr = page_address(page);
                        *dma_handle = addr;
                }
        }

        if (!vaddr)
                vaddr = swiotlb_alloc_coherent(dev, size, dma_handle, gfp);

        if (!vaddr)
                return NULL;

        /* Clear the SME encryption bit for DMA use if not swiotlb area */
        if (!is_swiotlb_buffer(dma_to_phys(dev, *dma_handle))) {
                set_memory_decrypted((unsigned long)vaddr, 1 << order);
                memset(vaddr, 0, PAGE_SIZE << order);
                *dma_handle = __sme_clr(*dma_handle);
        }

        return vaddr;
}

static void sev_free(struct device *dev, size_t size, void *vaddr,
                     dma_addr_t dma_handle, unsigned long attrs)
{
        /* Set the SME encryption bit for re-use if not swiotlb area */
        if (!is_swiotlb_buffer(dma_to_phys(dev, dma_handle)))
                set_memory_encrypted((unsigned long)vaddr,
                                     1 << get_order(size));

        swiotlb_free_coherent(dev, size, vaddr, dma_handle);
}

static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
{
        pgprot_t old_prot, new_prot;
        unsigned long pfn, pa, size;
        pte_t new_pte;

        switch (level) {
        case PG_LEVEL_4K:
                pfn = pte_pfn(*kpte);
                old_prot = pte_pgprot(*kpte);
                break;
        case PG_LEVEL_2M:
                pfn = pmd_pfn(*(pmd_t *)kpte);
                old_prot = pmd_pgprot(*(pmd_t *)kpte);
                break;
        case PG_LEVEL_1G:
                pfn = pud_pfn(*(pud_t *)kpte);
                old_prot = pud_pgprot(*(pud_t *)kpte);
                break;
        default:
                return;
        }

        new_prot = old_prot;
        if (enc)
                pgprot_val(new_prot) |= _PAGE_ENC;
        else
                pgprot_val(new_prot) &= ~_PAGE_ENC;

        /* If prot is same then do nothing. */
        if (pgprot_val(old_prot) == pgprot_val(new_prot))
                return;

        pa = pfn << page_level_shift(level);
        size = page_level_size(level);

        /*
         * We are going to perform in-place en-/decryption and change the
         * physical page attribute from C=1 to C=0 or vice versa. Flush the
         * caches to ensure that data gets accessed with the correct C-bit.
         */
        clflush_cache_range(__va(pa), size);

        /* Encrypt/decrypt the contents in-place */
        if (enc)
                sme_early_encrypt(pa, size);
        else
                sme_early_decrypt(pa, size);

        /* Change the page encryption mask. */
        new_pte = pfn_pte(pfn, new_prot);
        set_pte_atomic(kpte, new_pte);
}

static int __init early_set_memory_enc_dec(unsigned long vaddr,
                                           unsigned long size, bool enc)
{
        unsigned long vaddr_end, vaddr_next;
        unsigned long psize, pmask;
        int split_page_size_mask;
        int level, ret;
        pte_t *kpte;

        vaddr_next = vaddr;
        vaddr_end = vaddr + size;

        for (; vaddr < vaddr_end; vaddr = vaddr_next) {
                kpte = lookup_address(vaddr, &level);
                if (!kpte || pte_none(*kpte)) {
                        ret = 1;
                        goto out;
                }

                if (level == PG_LEVEL_4K) {
                        __set_clr_pte_enc(kpte, level, enc);
                        vaddr_next = (vaddr & PAGE_MASK) + PAGE_SIZE;
                        continue;
                }

                psize = page_level_size(level);
                pmask = page_level_mask(level);

                /*
                 * Check whether we can change the large page in one go.
                 * We request a split when the address is not aligned and
                 * the number of pages to set/clear encryption bit is smaller
                 * than the number of pages in the large page.
                 */
                if (vaddr == (vaddr & pmask) &&
                    ((vaddr_end - vaddr) >= psize)) {
                        __set_clr_pte_enc(kpte, level, enc);
                        vaddr_next = (vaddr & pmask) + psize;
                        continue;
                }

                /*
                 * The virtual address is part of a larger page, create the next
                 * level page table mapping (4K or 2M). If it is part of a 2M
                 * page then we request a split of the large page into 4K
                 * chunks. A 1GB large page is split into 2M pages, resp.
                 */
                if (level == PG_LEVEL_2M)
                        split_page_size_mask = 0;
                else
                        split_page_size_mask = 1 << PG_LEVEL_2M;

                kernel_physical_mapping_init(__pa(vaddr & pmask),
                                             __pa((vaddr_end & pmask) + psize),
                                             split_page_size_mask);
        }

        ret = 0;

out:
        __flush_tlb_all();
        return ret;
}

int __init early_set_memory_decrypted(unsigned long vaddr, unsigned long size)
{
        return early_set_memory_enc_dec(vaddr, size, false);
}

int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
{
        return early_set_memory_enc_dec(vaddr, size, true);
}

/*
 * SME and SEV are very similar but they are not the same, so there are
 * times that the kernel will need to distinguish between SME and SEV. The
 * sme_active() and sev_active() functions are used for this.  When a
 * distinction isn't needed, the mem_encrypt_active() function can be used.
 *
 * The trampoline code is a good example for this requirement.  Before
 * paging is activated, SME will access all memory as decrypted, but SEV
 * will access all memory as encrypted.  So, when APs are being brought
 * up under SME the trampoline area cannot be encrypted, whereas under SEV
 * the trampoline area must be encrypted.
 */
bool sme_active(void)
{
        return sme_me_mask && !sev_enabled;
}
EXPORT_SYMBOL_GPL(sme_active);

bool sev_active(void)
{
        return sme_me_mask && sev_enabled;
}
EXPORT_SYMBOL_GPL(sev_active);

static const struct dma_map_ops sev_dma_ops = {
        .alloc                  = sev_alloc,
        .free                   = sev_free,
        .map_page               = swiotlb_map_page,
        .unmap_page             = swiotlb_unmap_page,
        .map_sg                 = swiotlb_map_sg_attrs,
        .unmap_sg               = swiotlb_unmap_sg_attrs,
        .sync_single_for_cpu    = swiotlb_sync_single_for_cpu,
        .sync_single_for_device = swiotlb_sync_single_for_device,
        .sync_sg_for_cpu        = swiotlb_sync_sg_for_cpu,
        .sync_sg_for_device     = swiotlb_sync_sg_for_device,
        .mapping_error          = swiotlb_dma_mapping_error,
};

/* 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();

        /*
         * With SEV, DMA operations cannot use encryption. New DMA ops
         * are required in order to mark the DMA areas as decrypted or
         * to use bounce buffers.
         */
        if (sev_active())
                dma_ops = &sev_dma_ops;

        /*
         * With SEV, we need to unroll the rep string I/O instructions.
         */
        if (sev_active())
                static_branch_enable(&sev_enable_key);

        pr_info("AMD %s active\n",
                sev_active() ? "Secure Encrypted Virtualization (SEV)"
                             : "Secure Memory Encryption (SME)");
}

void swiotlb_set_mem_attributes(void *vaddr, unsigned long size)
{
        WARN(PAGE_ALIGN(size) != size,
             "size is not page-aligned (%#lx)\n", size);

        /* Make the SWIOTLB buffer area decrypted */
        set_memory_decrypted((unsigned long)vaddr, size >> PAGE_SHIFT);
}

static void __init sme_clear_pgd(pgd_t *pgd_base, unsigned long start,
                                 unsigned long end)
{
        unsigned long pgd_start, pgd_end, pgd_size;
        pgd_t *pgd_p;

        pgd_start = start & PGDIR_MASK;
        pgd_end = end & PGDIR_MASK;

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

        pgd_p = pgd_base + pgd_index(start);

        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       (__PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL)

static void __init *sme_populate_pgd(pgd_t *pgd_base, void *pgtable_area,
                                     unsigned long vaddr, pmdval_t pmd_val)
{
        pgd_t *pgd_p;
        p4d_t *p4d_p;
        pud_t *pud_p;
        pmd_t *pmd_p;

        pgd_p = pgd_base + pgd_index(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 = pgtable_area;
                        memset(p4d_p, 0, sizeof(*p4d_p) * PTRS_PER_P4D);
                        pgtable_area += sizeof(*p4d_p) * PTRS_PER_P4D;

                        pgd = native_make_pgd((pgdval_t)p4d_p + PGD_FLAGS);
                } else {
                        pud_p = pgtable_area;
                        memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);
                        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(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 = pgtable_area;
                        memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);
                        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(vaddr);
        if (native_pud_val(*pud_p)) {
                if (native_pud_val(*pud_p) & _PAGE_PSE)
                        goto out;

                pmd_p = (pmd_t *)(native_pud_val(*pud_p) & ~PTE_FLAGS_MASK);
        } else {
                pud_t pud;

                pmd_p = pgtable_area;
                memset(pmd_p, 0, sizeof(*pmd_p) * PTRS_PER_PMD);
                pgtable_area += sizeof(*pmd_p) * PTRS_PER_PMD;

                pud = native_make_pud((pmdval_t)pmd_p + PUD_FLAGS);
                native_set_pud(pud_p, pud);
        }

        pmd_p += pmd_index(vaddr);
        if (!native_pmd_val(*pmd_p) || !(native_pmd_val(*pmd_p) & _PAGE_PSE))
                native_set_pmd(pmd_p, native_make_pmd(pmd_val));

out:
        return pgtable_area;
}

static unsigned long __init sme_pgtable_calc(unsigned long len)
{
        unsigned long p4d_size, pud_size, pmd_size;
        unsigned long total;

        /*
         * Perform a relatively simplistic calculation of the pagetable
         * entries that are needed. That mappings will be covered by 2MB
         * PMD entries so we can conservatively calculate the required
         * number of P4D, PUD and PMD structures needed to perform the
         * mappings. 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;

        total = p4d_size + pud_size + pmd_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 sme_encrypt_kernel(void)
{
        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 pgtable_area_len;
        unsigned long paddr, pmd_flags;
        unsigned long decrypted_base;
        void *pgtable_area;
        pgd_t *pgd;

        if (!sme_active())
                return;

        /*
         * Prepare for encrypting the kernel 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 as encrypted.
         *
         *   Another range of virtual addresses will map the memory occupied
         *   by the kernel 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;

        /* 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;

        /* 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.
         */
        workarea_len = execute_len + pgtable_area_len;
        workarea_end = workarea_start + workarea_len;

        /*
         * 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.
         */
        pgtable_area = (void *)execute_end;

        /*
         * Make sure the current pagetable structure has entries for
         * addressing the workarea.
         */
        pgd = (pgd_t *)native_read_cr3_pa();
        paddr = workarea_start;
        while (paddr < workarea_end) {
                pgtable_area = sme_populate_pgd(pgd, pgtable_area,
                                                paddr,
                                                paddr + PMD_FLAGS);

                paddr += PMD_PAGE_SIZE;
        }

        /* 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
         * 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.
         */
        pgd = pgtable_area;
        memset(pgd, 0, sizeof(*pgd) * PTRS_PER_PGD);
        pgtable_area += sizeof(*pgd) * PTRS_PER_PGD;

        /* Add encrypted kernel (identity) mappings */
        pmd_flags = PMD_FLAGS | _PAGE_ENC;
        paddr = kernel_start;
        while (paddr < kernel_end) {
                pgtable_area = sme_populate_pgd(pgd, pgtable_area,
                                                paddr,
                                                paddr + pmd_flags);

                paddr += PMD_PAGE_SIZE;
        }

        /*
         * 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);
        decrypted_base <<= PGDIR_SHIFT;

        /* Add decrypted, write-protected kernel (non-identity) mappings */
        pmd_flags = (PMD_FLAGS & ~_PAGE_CACHE_MASK) | (_PAGE_PAT | _PAGE_PWT);
        paddr = kernel_start;
        while (paddr < kernel_end) {
                pgtable_area = sme_populate_pgd(pgd, pgtable_area,
                                                paddr + decrypted_base,
                                                paddr + pmd_flags);

                paddr += PMD_PAGE_SIZE;
        }

        /* Add decrypted workarea mappings to both kernel mappings */
        paddr = workarea_start;
        while (paddr < workarea_end) {
                pgtable_area = sme_populate_pgd(pgd, pgtable_area,
                                                paddr,
                                                paddr + PMD_FLAGS);

                pgtable_area = sme_populate_pgd(pgd, pgtable_area,
                                                paddr + decrypted_base,
                                                paddr + PMD_FLAGS);

                paddr += PMD_PAGE_SIZE;
        }

        /* Perform the encryption */
        sme_encrypt_execute(kernel_start, kernel_start + decrypted_base,
                            kernel_len, workarea_start, (unsigned long)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.
         */
        sme_clear_pgd(pgd, kernel_start + decrypted_base,
                      kernel_end + decrypted_base);

        sme_clear_pgd(pgd, workarea_start + decrypted_base,
                      workarea_end + decrypted_base);

        /* 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;
}