[PATCHv2 19/59] x86/mm: Implement syncing per-KeyID direct mappings

Kirill A. Shutemov
2019-07-31T15:21:50Z

For MKTME we use per-KeyID direct mappings. This allows kernel to have
access to encrypted memory.

sync_direct_mapping() sync per-KeyID direct mappings with a canonical
one -- KeyID-0.

The function tracks changes in the canonical mapping:
- creating or removing chunks of the translation tree;
- changes in mapping flags (i.e. protection bits);
- splitting huge page mapping into a page table;
- replacing page table with a huge page mapping;

The function need to be called on every change to the direct mapping:
hotplug, hotremove, changes in permissions bits, etc.

The function is nop until MKTME is enabled.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/x86/include/asm/mktme.h | 6 +
arch/x86/mm/init_64.c | 7 +
arch/x86/mm/mktme.c | 439 +++++++++++++++++++++++++++++++++++
arch/x86/mm/pageattr.c | 27 +++
4 files changed, 479 insertions(+)

diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h
index 3fc246acc279..d26ada6b65f7 100644
--- a/arch/x86/include/asm/mktme.h
+++ b/arch/x86/include/asm/mktme.h
@@ -62,6 +62,8 @@ static inline void arch_free_page(struct page *page, int order)
free_encrypted_page(page, order);
}

+int sync_direct_mapping(unsigned long start, unsigned long end);
+
#else
#define mktme_keyid_mask() ((phys_addr_t)0)
#define mktme_nr_keyids() 0
@@ -76,6 +78,10 @@ static inline bool mktme_enabled(void)

static inline void mktme_disable(void) {}

+static inline int sync_direct_mapping(unsigned long start, unsigned long end)
+{
+ return 0;
+}
#endif

#endif
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 4c1f93df47a5..6769650ad18d 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -726,6 +726,7 @@ __kernel_physical_mapping_init(unsigned long paddr_start,
{
bool pgd_changed = false;
unsigned long vaddr, vaddr_start, vaddr_end, vaddr_next, paddr_last;
+ int ret;

paddr_last = paddr_end;
vaddr = (unsigned long)__va(paddr_start);
@@ -762,6 +763,9 @@ __kernel_physical_mapping_init(unsigned long paddr_start,
pgd_changed = true;
}

+ ret = sync_direct_mapping(vaddr_start, vaddr_end);
+ WARN_ON(ret);
+
if (pgd_changed)
sync_global_pgds(vaddr_start, vaddr_end - 1);

@@ -1201,10 +1205,13 @@ void __ref vmemmap_free(unsigned long start, unsigned long end,
static void __meminit
kernel_physical_mapping_remove(unsigned long start, unsigned long end)
{
+ int ret;
start = (unsigned long)__va(start);
end = (unsigned long)__va(end);

remove_pagetable(start, end, true, NULL);
+ ret = sync_direct_mapping(start, end);
+ WARN_ON(ret);
}

void __ref arch_remove_memory(int nid, u64 start, u64 size,
diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c
index 1e8d662e5bff..ed13967bb543 100644
--- a/arch/x86/mm/mktme.c
+++ b/arch/x86/mm/mktme.c
@@ -1,6 +1,8 @@
#include <linux/mm.h>
#include <linux/highmem.h>
#include <asm/mktme.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>

/* Mask to extract KeyID from physical address. */
phys_addr_t __mktme_keyid_mask;
@@ -54,6 +56,8 @@ static bool need_page_mktme(void)
static void init_page_mktme(void)
{
static_branch_enable(&mktme_enabled_key);
+
+ sync_direct_mapping(PAGE_OFFSET, PAGE_OFFSET + direct_mapping_size);
}

struct page_ext_operations page_mktme_ops = {
@@ -148,3 +152,438 @@ void free_encrypted_page(struct page *page, int order)
page++;
}
}
+
+static int sync_direct_mapping_pte(unsigned long keyid,
+ pmd_t *dst_pmd, pmd_t *src_pmd,
+ unsigned long addr, unsigned long end)
+{
+ pte_t *src_pte, *dst_pte;
+ pte_t *new_pte = NULL;
+ bool remove_pte;
+
+ /*
+ * We want to unmap and free the page table if the source is empty and
+ * the range covers whole page table.
+ */
+ remove_pte = !src_pmd && PAGE_ALIGNED(addr) && PAGE_ALIGNED(end);
+
+ /*
+ * PMD page got split into page table.
+ * Clear PMD mapping. Page table will be established instead.
+ */
+ if (pmd_large(*dst_pmd)) {
+ spin_lock(&init_mm.page_table_lock);
+ pmd_clear(dst_pmd);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ /* Allocate a new page table if needed. */
+ if (pmd_none(*dst_pmd)) {
+ new_pte = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+ if (!new_pte)
+ return -ENOMEM;
+ dst_pte = new_pte + pte_index(addr + keyid * direct_mapping_size);
+ } else {
+ dst_pte = pte_offset_map(dst_pmd, addr + keyid * direct_mapping_size);
+ }
+ src_pte = src_pmd ? pte_offset_map(src_pmd, addr) : NULL;
+
+ spin_lock(&init_mm.page_table_lock);
+
+ do {
+ pteval_t val;
+
+ if (!src_pte || pte_none(*src_pte)) {
+ set_pte(dst_pte, __pte(0));
+ goto next;
+ }
+
+ if (!pte_none(*dst_pte)) {
+ /*
+ * Sanity check: PFNs must match between source
+ * and destination even if the rest doesn't.
+ */
+ BUG_ON(pte_pfn(*dst_pte) != pte_pfn(*src_pte));
+ }
+
+ /* Copy entry, but set KeyID. */
+ val = pte_val(*src_pte) | keyid << mktme_keyid_shift();
+ val &= __supported_pte_mask;
+ set_pte(dst_pte, __pte(val));
+next:
+ addr += PAGE_SIZE;
+ dst_pte++;
+ if (src_pte)
+ src_pte++;
+ } while (addr != end);
+
+ if (new_pte)
+ pmd_populate_kernel(&init_mm, dst_pmd, new_pte);
+
+ if (remove_pte) {
+ __free_page(pmd_page(*dst_pmd));
+ pmd_clear(dst_pmd);
+ }
+
+ spin_unlock(&init_mm.page_table_lock);
+
+ return 0;
+}
+
+static int sync_direct_mapping_pmd(unsigned long keyid,
+ pud_t *dst_pud, pud_t *src_pud,
+ unsigned long addr, unsigned long end)
+{
+ pmd_t *src_pmd, *dst_pmd;
+ pmd_t *new_pmd = NULL;
+ bool remove_pmd = false;
+ unsigned long next;
+ int ret = 0;
+
+ /*
+ * We want to unmap and free the page table if the source is empty and
+ * the range covers whole page table.
+ */
+ remove_pmd = !src_pud && IS_ALIGNED(addr, PUD_SIZE) && IS_ALIGNED(end, PUD_SIZE);
+
+ /*
+ * PUD page got split into page table.
+ * Clear PUD mapping. Page table will be established instead.
+ */
+ if (pud_large(*dst_pud)) {
+ spin_lock(&init_mm.page_table_lock);
+ pud_clear(dst_pud);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ /* Allocate a new page table if needed. */
+ if (pud_none(*dst_pud)) {
+ new_pmd = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+ if (!new_pmd)
+ return -ENOMEM;
+ dst_pmd = new_pmd + pmd_index(addr + keyid * direct_mapping_size);
+ } else {
+ dst_pmd = pmd_offset(dst_pud, addr + keyid * direct_mapping_size);
+ }
+ src_pmd = src_pud ? pmd_offset(src_pud, addr) : NULL;
+
+ do {
+ pmd_t *__src_pmd = src_pmd;
+
+ next = pmd_addr_end(addr, end);
+ if (!__src_pmd || pmd_none(*__src_pmd)) {
+ if (pmd_none(*dst_pmd))
+ goto next;
+ if (pmd_large(*dst_pmd)) {
+ spin_lock(&init_mm.page_table_lock);
+ set_pmd(dst_pmd, __pmd(0));
+ spin_unlock(&init_mm.page_table_lock);
+ goto next;
+ }
+ __src_pmd = NULL;
+ }
+
+ if (__src_pmd && pmd_large(*__src_pmd)) {
+ pmdval_t val;
+
+ if (pmd_large(*dst_pmd)) {
+ /*
+ * Sanity check: PFNs must match between source
+ * and destination even if the rest doesn't.
+ */
+ BUG_ON(pmd_pfn(*dst_pmd) != pmd_pfn(*__src_pmd));
+ } else if (!pmd_none(*dst_pmd)) {
+ /*
+ * Page table is replaced with a PMD page.
+ * Free and unmap the page table.
+ */
+ __free_page(pmd_page(*dst_pmd));
+ spin_lock(&init_mm.page_table_lock);
+ pmd_clear(dst_pmd);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ /* Copy entry, but set KeyID. */
+ val = pmd_val(*__src_pmd) | keyid << mktme_keyid_shift();
+ val &= __supported_pte_mask;
+ spin_lock(&init_mm.page_table_lock);
+ set_pmd(dst_pmd, __pmd(val));
+ spin_unlock(&init_mm.page_table_lock);
+ goto next;
+ }
+
+ ret = sync_direct_mapping_pte(keyid, dst_pmd, __src_pmd,
+ addr, next);
+next:
+ addr = next;
+ dst_pmd++;
+ if (src_pmd)
+ src_pmd++;
+ } while (addr != end && !ret);
+
+ if (new_pmd) {
+ spin_lock(&init_mm.page_table_lock);
+ pud_populate(&init_mm, dst_pud, new_pmd);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ if (remove_pmd) {
+ spin_lock(&init_mm.page_table_lock);
+ __free_page(pud_page(*dst_pud));
+ pud_clear(dst_pud);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ return ret;
+}
+
+static int sync_direct_mapping_pud(unsigned long keyid,
+ p4d_t *dst_p4d, p4d_t *src_p4d,
+ unsigned long addr, unsigned long end)
+{
+ pud_t *src_pud, *dst_pud;
+ pud_t *new_pud = NULL;
+ bool remove_pud = false;
+ unsigned long next;
+ int ret = 0;
+
+ /*
+ * We want to unmap and free the page table if the source is empty and
+ * the range covers whole page table.
+ */
+ remove_pud = !src_p4d && IS_ALIGNED(addr, P4D_SIZE) && IS_ALIGNED(end, P4D_SIZE);
+
+ /*
+ * P4D page got split into page table.
+ * Clear P4D mapping. Page table will be established instead.
+ */
+ if (p4d_large(*dst_p4d)) {
+ spin_lock(&init_mm.page_table_lock);
+ p4d_clear(dst_p4d);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ /* Allocate a new page table if needed. */
+ if (p4d_none(*dst_p4d)) {
+ new_pud = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+ if (!new_pud)
+ return -ENOMEM;
+ dst_pud = new_pud + pud_index(addr + keyid * direct_mapping_size);
+ } else {
+ dst_pud = pud_offset(dst_p4d, addr + keyid * direct_mapping_size);
+ }
+ src_pud = src_p4d ? pud_offset(src_p4d, addr) : NULL;
+
+ do {
+ pud_t *__src_pud = src_pud;
+
+ next = pud_addr_end(addr, end);
+ if (!__src_pud || pud_none(*__src_pud)) {
+ if (pud_none(*dst_pud))
+ goto next;
+ if (pud_large(*dst_pud)) {
+ spin_lock(&init_mm.page_table_lock);
+ set_pud(dst_pud, __pud(0));
+ spin_unlock(&init_mm.page_table_lock);
+ goto next;
+ }
+ __src_pud = NULL;
+ }
+
+ if (__src_pud && pud_large(*__src_pud)) {
+ pudval_t val;
+
+ if (pud_large(*dst_pud)) {
+ /*
+ * Sanity check: PFNs must match between source
+ * and destination even if the rest doesn't.
+ */
+ BUG_ON(pud_pfn(*dst_pud) != pud_pfn(*__src_pud));
+ } else if (!pud_none(*dst_pud)) {
+ /*
+ * Page table is replaced with a pud page.
+ * Free and unmap the page table.
+ */
+ __free_page(pud_page(*dst_pud));
+ spin_lock(&init_mm.page_table_lock);
+ pud_clear(dst_pud);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ /* Copy entry, but set KeyID. */
+ val = pud_val(*__src_pud) | keyid << mktme_keyid_shift();
+ val &= __supported_pte_mask;
+ spin_lock(&init_mm.page_table_lock);
+ set_pud(dst_pud, __pud(val));
+ spin_unlock(&init_mm.page_table_lock);
+ goto next;
+ }
+
+ ret = sync_direct_mapping_pmd(keyid, dst_pud, __src_pud,
+ addr, next);
+next:
+ addr = next;
+ dst_pud++;
+ if (src_pud)
+ src_pud++;
+ } while (addr != end && !ret);
+
+ if (new_pud) {
+ spin_lock(&init_mm.page_table_lock);
+ p4d_populate(&init_mm, dst_p4d, new_pud);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ if (remove_pud) {
+ spin_lock(&init_mm.page_table_lock);
+ __free_page(p4d_page(*dst_p4d));
+ p4d_clear(dst_p4d);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ return ret;
+}
+
+static int sync_direct_mapping_p4d(unsigned long keyid,
+ pgd_t *dst_pgd, pgd_t *src_pgd,
+ unsigned long addr, unsigned long end)
+{
+ p4d_t *src_p4d, *dst_p4d;
+ p4d_t *new_p4d_1 = NULL, *new_p4d_2 = NULL;
+ bool remove_p4d = false;
+ unsigned long next;
+ int ret = 0;
+
+ /*
+ * We want to unmap and free the page table if the source is empty and
+ * the range covers whole page table.
+ */
+ remove_p4d = !src_pgd && IS_ALIGNED(addr, PGDIR_SIZE) && IS_ALIGNED(end, PGDIR_SIZE);
+
+ /* Allocate a new page table if needed. */
+ if (pgd_none(*dst_pgd)) {
+ new_p4d_1 = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+ if (!new_p4d_1)
+ return -ENOMEM;
+ dst_p4d = new_p4d_1 + p4d_index(addr + keyid * direct_mapping_size);
+ } else {
+ dst_p4d = p4d_offset(dst_pgd, addr + keyid * direct_mapping_size);
+ }
+ src_p4d = src_pgd ? p4d_offset(src_pgd, addr) : NULL;
+
+ do {
+ p4d_t *__src_p4d = src_p4d;
+
+ next = p4d_addr_end(addr, end);
+ if (!__src_p4d || p4d_none(*__src_p4d)) {
+ if (p4d_none(*dst_p4d))
+ goto next;
+ __src_p4d = NULL;
+ }
+
+ ret = sync_direct_mapping_pud(keyid, dst_p4d, __src_p4d,
+ addr, next);
+next:
+ addr = next;
+ dst_p4d++;
+
+ /*
+ * Direct mappings are 1TiB-aligned. With 5-level paging it
+ * means that on PGD level there can be misalignment between
+ * source and distiantion.
+ *
+ * Allocate the new page table if dst_p4d crosses page table
+ * boundary.
+ */
+ if (!((unsigned long)dst_p4d & ~PAGE_MASK) && addr != end) {
+ if (pgd_none(dst_pgd[1])) {
+ new_p4d_2 = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+ if (!new_p4d_2)
+ ret = -ENOMEM;
+ dst_p4d = new_p4d_2;
+ } else {
+ dst_p4d = p4d_offset(dst_pgd + 1, 0);
+ }
+ }
+ if (src_p4d)
+ src_p4d++;
+ } while (addr != end && !ret);
+
+ if (new_p4d_1 || new_p4d_2) {
+ spin_lock(&init_mm.page_table_lock);
+ if (new_p4d_1)
+ pgd_populate(&init_mm, dst_pgd, new_p4d_1);
+ if (new_p4d_2)
+ pgd_populate(&init_mm, dst_pgd + 1, new_p4d_2);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ if (remove_p4d) {
+ spin_lock(&init_mm.page_table_lock);
+ __free_page(pgd_page(*dst_pgd));
+ pgd_clear(dst_pgd);
+ spin_unlock(&init_mm.page_table_lock);
+ }
+
+ return ret;
+}
+
+static int sync_direct_mapping_keyid(unsigned long keyid,
+ unsigned long addr, unsigned long end)
+{
+ pgd_t *src_pgd, *dst_pgd;
+ unsigned long next;
+ int ret = 0;
+
+ dst_pgd = pgd_offset_k(addr + keyid * direct_mapping_size);
+ src_pgd = pgd_offset_k(addr);
+
+ do {
+ pgd_t *__src_pgd = src_pgd;
+
+ next = pgd_addr_end(addr, end);
+ if (pgd_none(*__src_pgd)) {
+ if (pgd_none(*dst_pgd))
+ continue;
+ __src_pgd = NULL;
+ }
+
+ ret = sync_direct_mapping_p4d(keyid, dst_pgd, __src_pgd,
+ addr, next);
+ } while (dst_pgd++, src_pgd++, addr = next, addr != end && !ret);
+
+ return ret;
+}
+
+/*
+ * For MKTME we maintain per-KeyID direct mappings. This allows kernel to have
+ * access to encrypted memory.
+ *
+ * sync_direct_mapping() sync per-KeyID direct mappings with a canonical
+ * one -- KeyID-0.
+ *
+ * The function tracks changes in the canonical mapping:
+ * - creating or removing chunks of the translation tree;
+ * - changes in mapping flags (i.e. protection bits);
+ * - splitting huge page mapping into a page table;
+ * - replacing page table with a huge page mapping;
+ *
+ * The function need to be called on every change to the direct mapping:
+ * hotplug, hotremove, changes in permissions bits, etc.
+ *
+ * The function is nop until MKTME is enabled.
+ */
+int sync_direct_mapping(unsigned long start, unsigned long end)
+{
+ int i, ret = 0;
+
+ if (!mktme_enabled())
+ return 0;
+
+ for (i = 1; !ret && i <= mktme_nr_keyids(); i++)
+ ret = sync_direct_mapping_keyid(i, start, end);
+
+ flush_tlb_all();
+
+ return ret;
+}
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 6a9a77a403c9..f4e3205d2cdd 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -347,6 +347,33 @@ static void cpa_flush(struct cpa_data *data, int cache)

BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);

+ if (mktme_enabled()) {
+ unsigned long start, end;
+
+ start = PAGE_OFFSET + (cpa->pfn << PAGE_SHIFT);
+ end = start + cpa->numpages * PAGE_SIZE;
+
+ /* Round to cover huge page possibly split by the change */
+ start = round_down(start, direct_gbpages ? PUD_SIZE : PMD_SIZE);
+ end = round_up(end, direct_gbpages ? PUD_SIZE : PMD_SIZE);
+
+ /* Sync all direct mapping for an array */
+ if (cpa->flags & CPA_ARRAY) {
+ start = PAGE_OFFSET;
+ end = PAGE_OFFSET + direct_mapping_size;
+ }
+
+ /*
+ * Sync per-KeyID direct mappings with the canonical one
+ * (KeyID-0).
+ *
+ * sync_direct_mapping() does full TLB flush.
+ */
+ sync_direct_mapping(start, end);
+ if (!cache)
+ return;
+ }
+
if (cache && !static_cpu_has(X86_FEATURE_CLFLUSH)) {
cpa_flush_all(cache);
return;
--
2.21.0