swh:1:snp:173f8deb0c56c557784b4fd217e7608ac6197844
Tip revision: 36a21d51725af2ce0700c6ebcb6b9594aac658a6 authored by Linus Torvalds on 08 August 2021, 20:49:31 UTC
Linux 5.14-rc5
Linux 5.14-rc5
Tip revision: 36a21d5
mem_encrypt.c
// 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 <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/processor-flags.h>
#include <asm/msr.h>
#include <asm/cmdline.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);
DEFINE_STATIC_KEY_FALSE(sev_enable_key);
EXPORT_SYMBOL_GPL(sev_enable_key);
/* Buffer used for early in-place encryption by BSP, no locking needed */
static char sme_early_buffer[PAGE_SIZE] __initdata __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);
flush_tlb_local();
}
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;
}
void __init sev_setup_arch(void)
{
phys_addr_t total_mem = memblock_phys_mem_size();
unsigned long size;
if (!sev_active())
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);
}
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_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);
/* 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_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;
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 sev_active(void)
{
return sev_status & MSR_AMD64_SEV_ENABLED;
}
bool sme_active(void)
{
return sme_me_mask && !sev_active();
}
EXPORT_SYMBOL_GPL(sev_active);
/* Needs to be called from non-instrumentable code */
bool noinstr sev_es_active(void)
{
return sev_status & MSR_AMD64_SEV_ES_ENABLED;
}
/* 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 (sev_active())
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 (sme_active()) {
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;
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 (mem_encrypt_active()) {
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);
}
static void print_mem_encrypt_feature_info(void)
{
pr_info("AMD Memory Encryption Features active:");
/* Secure Memory Encryption */
if (sme_active()) {
/*
* SME is mutually exclusive with any of the SEV
* features below.
*/
pr_cont(" SME\n");
return;
}
/* Secure Encrypted Virtualization */
if (sev_active())
pr_cont(" SEV");
/* Encrypted Register State */
if (sev_es_active())
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();
/*
* With SEV, we need to unroll the rep string I/O instructions,
* but SEV-ES supports them through the #VC handler.
*/
if (sev_active() && !sev_es_active())
static_branch_enable(&sev_enable_key);
print_mem_encrypt_feature_info();
}
int arch_has_restricted_virtio_memory_access(void)
{
return sev_active();
}
EXPORT_SYMBOL_GPL(arch_has_restricted_virtio_memory_access);