// SPDX-License-Identifier: GPL-2.0-only
/*
 * AMD Memory Encryption Support
 *
 * Copyright (C) 2016-2024 Advanced Micro Devices, Inc.
 *
 * Author: Tom Lendacky <thomas.lendacky@amd.com>
 */

#include <linux/linkage.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/dma-direct.h>
#include <linux/swiotlb.h>
#include <linux/mem_encrypt.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/bitops.h>
#include <linux/dma-mapping.h>
#include <linux/cc_platform.h>

#include <asm/tlbflush.h>
#include <asm/fixmap.h>
#include <asm/setup.h>
#include <asm/mem_encrypt.h>
#include <asm/bootparam.h>
#include <asm/set_memory.h>
#include <asm/cacheflush.h>
#include <asm/processor-flags.h>
#include <asm/msr.h>
#include <asm/cmdline.h>
#include <asm/sev.h>
#include <asm/ia32.h>

#include "mm_internal.h"

/*
 * 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;
SYM_PIC_ALIAS(sme_me_mask);
u64 sev_status __section(".data") = 0;
SYM_PIC_ALIAS(sev_status);
u64 sev_check_data __section(".data") = 0;
EXPORT_SYMBOL(sme_me_mask);

/* Buffer used for early in-place encryption by BSP, no locking needed */
static char sme_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE);

/*
 * SNP-specific routine which needs to additionally change the page state from
 * private to shared before copying the data from the source to destination and
 * restore after the copy.
 */
static inline void __init snp_memcpy(void *dst, void *src, size_t sz,
                                     unsigned long paddr, bool decrypt)
{
        unsigned long npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;

        if (decrypt) {
                /*
                 * @paddr needs to be accessed decrypted, mark the page shared in
                 * the RMP table before copying it.
                 */
                early_snp_set_memory_shared((unsigned long)__va(paddr), paddr, npages);

                memcpy(dst, src, sz);

                /* Restore the page state after the memcpy. */
                early_snp_set_memory_private((unsigned long)__va(paddr), paddr, npages);
        } else {
                /*
                 * @paddr need to be accessed encrypted, no need for the page state
                 * change.
                 */
                memcpy(dst, src, sz);
        }
}

/*
 * 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.
                 */
                if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) {
                        snp_memcpy(sme_early_buffer, src, len, paddr, enc);
                        snp_memcpy(dst, sme_early_buffer, len, paddr, !enc);
                } else {
                        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);

        flush_tlb_local();
}

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

        if (!cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
                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 (!cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
                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);
}

static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
{
        unsigned long pfn = 0;
        pgprot_t prot;

        switch (level) {
        case PG_LEVEL_4K:
                pfn = pte_pfn(*kpte);
                prot = pte_pgprot(*kpte);
                break;
        case PG_LEVEL_2M:
                pfn = pmd_pfn(*(pmd_t *)kpte);
                prot = pmd_pgprot(*(pmd_t *)kpte);
                break;
        case PG_LEVEL_1G:
                pfn = pud_pfn(*(pud_t *)kpte);
                prot = pud_pgprot(*(pud_t *)kpte);
                break;
        default:
                WARN_ONCE(1, "Invalid level for kpte\n");
                return 0;
        }

        if (ret_prot)
                *ret_prot = prot;

        return pfn;
}

static bool amd_enc_tlb_flush_required(bool enc)
{
        return true;
}

static bool amd_enc_cache_flush_required(void)
{
        return !cpu_feature_enabled(X86_FEATURE_SME_COHERENT);
}

static void enc_dec_hypercall(unsigned long vaddr, unsigned long size, bool enc)
{
#ifdef CONFIG_PARAVIRT
        unsigned long vaddr_end = vaddr + size;

        while (vaddr < vaddr_end) {
                int psize, pmask, level;
                unsigned long pfn;
                pte_t *kpte;

                kpte = lookup_address(vaddr, &level);
                if (!kpte || pte_none(*kpte)) {
                        WARN_ONCE(1, "kpte lookup for vaddr\n");
                        return;
                }

                pfn = pg_level_to_pfn(level, kpte, NULL);
                if (!pfn)
                        continue;

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

                notify_page_enc_status_changed(pfn, psize >> PAGE_SHIFT, enc);

                vaddr = (vaddr & pmask) + psize;
        }
#endif
}

static int amd_enc_status_change_prepare(unsigned long vaddr, int npages, bool enc)
{
        /*
         * To maintain the security guarantees of SEV-SNP guests, make sure
         * to invalidate the memory before encryption attribute is cleared.
         */
        if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP) && !enc)
                snp_set_memory_shared(vaddr, npages);

        return 0;
}

/* Return true unconditionally: return value doesn't matter for the SEV side */
static int amd_enc_status_change_finish(unsigned long vaddr, int npages, bool enc)
{
        /*
         * After memory is mapped encrypted in the page table, validate it
         * so that it is consistent with the page table updates.
         */
        if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP) && enc)
                snp_set_memory_private(vaddr, npages);

        if (!cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
                enc_dec_hypercall(vaddr, npages << PAGE_SHIFT, enc);

        return 0;
}

int prepare_pte_enc(struct pte_enc_desc *d)
{
        pgprot_t old_prot;

        d->pfn = pg_level_to_pfn(d->pte_level, d->kpte, &old_prot);
        if (!d->pfn)
                return 1;

        d->new_pgprot = old_prot;
        if (d->encrypt)
                pgprot_val(d->new_pgprot) |= _PAGE_ENC;
        else
                pgprot_val(d->new_pgprot) &= ~_PAGE_ENC;

        /* If prot is same then do nothing. */
        if (pgprot_val(old_prot) == pgprot_val(d->new_pgprot))
                return 1;

        d->pa = d->pfn << PAGE_SHIFT;
        d->size = page_level_size(d->pte_level);

        /*
         * In-place en-/decryption and physical page attribute change
         * from C=1 to C=0 or vice versa will be performed. Flush the
         * caches to ensure that data gets accessed with the correct
         * C-bit.
         */
        if (d->va)
                clflush_cache_range(d->va, d->size);
        else
                clflush_cache_range(__va(d->pa), d->size);

        return 0;
}

void set_pte_enc_mask(pte_t *kpte, unsigned long pfn, pgprot_t new_prot)
{
        pte_t new_pte;

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

static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
{
        struct pte_enc_desc d = {
                .kpte        = kpte,
                .pte_level   = level,
                .encrypt     = enc
        };

        if (prepare_pte_enc(&d))
                return;

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

                /*
                 * ON SNP, the page state in the RMP table must happen
                 * before the page table updates.
                 */
                early_snp_set_memory_shared((unsigned long)__va(d.pa), d.pa, 1);
        }

        set_pte_enc_mask(kpte, d.pfn, d.new_pgprot);

        /*
         * If page is set encrypted in the page table, then update the RMP table to
         * add this page as private.
         */
        if (enc)
                early_snp_set_memory_private((unsigned long)__va(d.pa), d.pa, 1);
}

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

        start = vaddr;
        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_change() does not flush the TLBs, so
                 * a TLB flush is required after we exit from the for loop.
                 */
                kernel_physical_mapping_change(__pa(vaddr & pmask),
                                               __pa((vaddr_end & pmask) + psize),
                                               split_page_size_mask);
        }

        ret = 0;

        early_set_mem_enc_dec_hypercall(start, size, enc);
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);
}

void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, unsigned long size, bool enc)
{
        enc_dec_hypercall(vaddr, size, enc);
}

void __init sme_early_init(void)
{
        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 */
        add_encrypt_protection_map();

        x86_platform.guest.enc_status_change_prepare = amd_enc_status_change_prepare;
        x86_platform.guest.enc_status_change_finish  = amd_enc_status_change_finish;
        x86_platform.guest.enc_tlb_flush_required    = amd_enc_tlb_flush_required;
        x86_platform.guest.enc_cache_flush_required  = amd_enc_cache_flush_required;
        x86_platform.guest.enc_kexec_begin           = snp_kexec_begin;
        x86_platform.guest.enc_kexec_finish          = snp_kexec_finish;

        /*
         * AMD-SEV-ES intercepts the RDMSR to read the X2APIC ID in the
         * parallel bringup low level code. That raises #VC which cannot be
         * handled there.
         * It does not provide a RDMSR GHCB protocol so the early startup
         * code cannot directly communicate with the secure firmware. The
         * alternative solution to retrieve the APIC ID via CPUID(0xb),
         * which is covered by the GHCB protocol, is not viable either
         * because there is no enforcement of the CPUID(0xb) provided
         * "initial" APIC ID to be the same as the real APIC ID.
         * Disable parallel bootup.
         */
        if (sev_status & MSR_AMD64_SEV_ES_ENABLED)
                x86_cpuinit.parallel_bringup = false;

        /*
         * The VMM is capable of injecting interrupt 0x80 and triggering the
         * compatibility syscall path.
         *
         * By default, the 32-bit emulation is disabled in order to ensure
         * the safety of the VM.
         */
        if (sev_status & MSR_AMD64_SEV_ENABLED)
                ia32_disable();

        /*
         * Override init functions that scan the ROM region in SEV-SNP guests,
         * as this memory is not pre-validated and would thus cause a crash.
         */
        if (sev_status & MSR_AMD64_SEV_SNP_ENABLED) {
                x86_init.mpparse.find_mptable = x86_init_noop;
                x86_init.pci.init_irq = x86_init_noop;
                x86_init.resources.probe_roms = x86_init_noop;

                /*
                 * DMI setup behavior for SEV-SNP guests depends on
                 * efi_enabled(EFI_CONFIG_TABLES), which hasn't been
                 * parsed yet. snp_dmi_setup() will run after that
                 * parsing has happened.
                 */
                x86_init.resources.dmi_setup = snp_dmi_setup;
        }

        if (sev_status & MSR_AMD64_SNP_SECURE_TSC)
                setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
}

void __init mem_encrypt_free_decrypted_mem(void)
{
        unsigned long vaddr, vaddr_end, npages;
        int r;

        vaddr = (unsigned long)__start_bss_decrypted_unused;
        vaddr_end = (unsigned long)__end_bss_decrypted;
        npages = (vaddr_end - vaddr) >> PAGE_SHIFT;

        /*
         * If the unused memory range was mapped decrypted, change the encryption
         * attribute from decrypted to encrypted before freeing it. Base the
         * re-encryption on the same condition used for the decryption in
         * sme_postprocess_startup(). Higher level abstractions, such as
         * CC_ATTR_MEM_ENCRYPT, aren't necessarily equivalent in a Hyper-V VM
         * using vTOM, where sme_me_mask is always zero.
         */
        if (sme_me_mask) {
                r = set_memory_encrypted(vaddr, npages);
                if (r) {
                        pr_warn("failed to free unused decrypted pages\n");
                        return;
                }
        }

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