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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * AMD Memory Encryption Support
  *
  * Copyright (C) 2016 Advanced Micro Devices, Inc.
  *
  * Author: Tom Lendacky <thomas.lendacky@amd.com>
  */
 
 #define DISABLE_BRANCH_PROFILING
 
 #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/virtio_config.h>
 #include <linux/virtio_anchor.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 "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;
 u64 sev_status __section(".data") = 0;
 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);
 }
 
 void __init sev_setup_arch(void)
 {
     phys_addr_t total_mem = memblock_phys_mem_size();
     unsigned long size;
 
     if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
         return;
 
     /*
      * For SEV, all DMA has to occur via shared/unencrypted pages.
      * SEV 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 for SEV guests 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);
 }
 
 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, int npages, bool enc)
 {
 #ifdef CONFIG_PARAVIRT
     unsigned long sz = npages << PAGE_SHIFT;
     unsigned long vaddr_end = vaddr + sz;
 
     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 void 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 true unconditionally: return value doesn't matter for the SEV side */
 static bool 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, enc);
 
     return true;
 }
 
 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;
 
     pfn = pg_level_to_pfn(level, kpte, &old_prot);
     if (!pfn)
         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_SHIFT;
     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);
 
         /*
          * ON SNP, the page state in the RMP table must happen
          * before the page table updates.
          */
         early_snp_set_memory_shared((unsigned long)__va(pa), pa, 1);
     }
 
     /* Change the page encryption mask. */
     new_pte = pfn_pte(pfn, new_prot);
     set_pte_atomic(kpte, new_pte);
 
     /*
      * 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(pa), 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, PAGE_ALIGN(size) >> PAGE_SHIFT, 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, int npages, bool enc)
 {
     enc_dec_hypercall(vaddr, npages, 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;
 }
 
 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;
 
     /*
      * The unused memory range was mapped decrypted, change the encryption
      * attribute from decrypted to encrypted before freeing it.
      */
     if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
         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);
 }

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