[PATCHv6 00/15] mm, x86/cc: Implement support for unaccepted memory

[PATCHv6 00/15] mm, x86/cc: Implement support for unaccepted memory

[Kirill A. Shutemov]

UEFI Specification version 2.9 introduces the concept of memory
acceptance: some Virtual Machine platforms, such as Intel TDX or AMD
SEV-SNP, requiring memory to be accepted before it can be used by the
guest. Accepting happens via a protocol specific for the Virtual
Machine platform.

Accepting memory is costly and it makes VMM allocate memory for the
accepted guest physical address range. It's better to postpone memory
acceptance until memory is needed. It lowers boot time and reduces
memory overhead.

The kernel needs to know what memory has been accepted. Firmware
communicates this information via memory map: a new memory type --
EFI_UNACCEPTED_MEMORY -- indicates such memory.

Range-based tracking works fine for firmware, but it gets bulky for
the kernel: e820 has to be modified on every page acceptance. It leads
to table fragmentation, but there's a limited number of entries in the
e820 table

Another option is to mark such memory as usable in e820 and track if the
range has been accepted in a bitmap. One bit in the bitmap represents
2MiB in the address space: one 4k page is enough to track 64GiB or
physical address space.

In the worst-case scenario -- a huge hole in the middle of the
address space -- It needs 256MiB to handle 4PiB of the address
space.

Any unaccepted memory that is not aligned to 2M gets accepted upfront.

The approach lowers boot time substantially. Boot to shell is ~2.5x
faster for 4G TDX VM and ~4x faster for 64G.

TDX-specific code isolated from the core of unaccepted memory support. It
supposed to help to plug-in different implementation of unaccepted memory
such as SEV-SNP.

The tree can be found here:

https://github.com/intel/tdx.git guest-unaccepted-memory

v6:
 - Fix load_unaligned_zeropad() on machine with unaccepted memory;
 - Clear PageUnaccepted() on merged pages, leaving it only on head;
 - Clarify error handling in allocate_e820();
 - Fix build with CONFIG_UNACCEPTED_MEMORY=y, but without TDX;
 - Disable kexec at boottime instead of build conflict;
 - Rebased to tip/master;
 - Spelling fixes;
 - Add Reviewed-by from Mike and David;
v5:
 - Updates comments and commit messages;
   + Explain options for unaccepted memory handling;
 - Expose amount of unaccepted memory in /proc/meminfo
 - Adjust check in page_expected_state();
 - Fix error code handling in allocate_e820();
 - Centralize __pa()/__va() definitions in the boot stub;
 - Avoid includes from the main kernel in the boot stub;
 - Use an existing hole in boot_param for unaccepted_memory, instead of adding
   to the end of the structure;
 - Extract allocate_unaccepted_memory() form allocate_e820();
 - Complain if there's unaccepted memory, but kernel does not support it;
 - Fix vmstat counter;
 - Split up few preparatory patches;
 - Random readability adjustments;
v4:
 - PageBuddyUnaccepted() -> PageUnaccepted;
 - Use separate page_type, not shared with offline;
 - Rework interface between core-mm and arch code;
 - Adjust commit messages;
 - Ack from Mike;
Kirill A. Shutemov (15):
  x86/boot: Centralize __pa()/__va() definitions
  mm: Add support for unaccepted memory
  efi/x86: Get full memory map in allocate_e820()
  x86/boot: Add infrastructure required for unaccepted memory support
  efi/x86: Implement support for unaccepted memory
  x86/boot/compressed: Handle unaccepted memory
  x86/mm: Reserve unaccepted memory bitmap
  x86/mm: Provide helpers for unaccepted memory
  x86/mm: Avoid load_unaligned_zeropad() stepping into unaccepted memory
  x86/mm: Report unaccepted memory in /proc/meminfo
  x86: Disable kexec if system has unaccepted memory
  x86/tdx: Make _tdx_hypercall() and __tdx_module_call() available in
    boot stub
  x86/tdx: Refactor try_accept_one()
  x86/tdx: Add unaccepted memory support
  mm/vmstat: Add counter for memory accepting

 Documentation/x86/zero-page.rst          |   1 +
 arch/x86/Kconfig                         |   1 +
 arch/x86/boot/bitops.h                   |  40 +++++++
 arch/x86/boot/compressed/Makefile        |   1 +
 arch/x86/boot/compressed/align.h         |  14 +++
 arch/x86/boot/compressed/bitmap.c        |  43 +++++++
 arch/x86/boot/compressed/bitmap.h        |  49 ++++++++
 arch/x86/boot/compressed/bits.h          |  36 ++++++
 arch/x86/boot/compressed/compiler.h      |   9 ++
 arch/x86/boot/compressed/efi.h           |   1 +
 arch/x86/boot/compressed/find.c          |  54 +++++++++
 arch/x86/boot/compressed/find.h          |  80 +++++++++++++
 arch/x86/boot/compressed/ident_map_64.c  |   8 --
 arch/x86/boot/compressed/kaslr.c         |  35 ++++--
 arch/x86/boot/compressed/math.h          |  37 ++++++
 arch/x86/boot/compressed/mem.c           | 111 +++++++++++++++++
 arch/x86/boot/compressed/minmax.h        |  61 ++++++++++
 arch/x86/boot/compressed/misc.c          |   6 +
 arch/x86/boot/compressed/misc.h          |  15 +++
 arch/x86/boot/compressed/pgtable_types.h |  25 ++++
 arch/x86/boot/compressed/sev.c           |   2 -
 arch/x86/boot/compressed/tdx.c           |  78 ++++++++++++
 arch/x86/coco/tdx/tdx.c                  |  94 +++++++--------
 arch/x86/include/asm/page.h              |   3 +
 arch/x86/include/asm/set_memory.h        |   2 +
 arch/x86/include/asm/shared/tdx.h        |  47 ++++++++
 arch/x86/include/asm/tdx.h               |  19 ---
 arch/x86/include/asm/unaccepted_memory.h |  25 ++++
 arch/x86/include/uapi/asm/bootparam.h    |   2 +-
 arch/x86/kernel/e820.c                   |  10 ++
 arch/x86/mm/Makefile                     |   2 +
 arch/x86/mm/init.c                       |   8 ++
 arch/x86/mm/pat/set_memory.c             |   2 +-
 arch/x86/mm/unaccepted_memory.c          | 144 +++++++++++++++++++++++
 drivers/firmware/efi/Kconfig             |  14 +++
 drivers/firmware/efi/efi.c               |   1 +
 drivers/firmware/efi/libstub/x86-stub.c  | 103 +++++++++++++---
 include/linux/efi.h                      |   3 +-
 include/linux/page-flags.h               |  31 +++++
 include/linux/vm_event_item.h            |   3 +
 mm/internal.h                            |  12 ++
 mm/memblock.c                            |   9 ++
 mm/page_alloc.c                          |  87 +++++++++++++-
 mm/vmstat.c                              |   3 +
 44 files changed, 1215 insertions(+), 116 deletions(-)
 create mode 100644 arch/x86/boot/compressed/align.h
 create mode 100644 arch/x86/boot/compressed/bitmap.c
 create mode 100644 arch/x86/boot/compressed/bitmap.h
 create mode 100644 arch/x86/boot/compressed/bits.h
 create mode 100644 arch/x86/boot/compressed/compiler.h
 create mode 100644 arch/x86/boot/compressed/find.c
 create mode 100644 arch/x86/boot/compressed/find.h
 create mode 100644 arch/x86/boot/compressed/math.h
 create mode 100644 arch/x86/boot/compressed/mem.c
 create mode 100644 arch/x86/boot/compressed/minmax.h
 create mode 100644 arch/x86/boot/compressed/pgtable_types.h
 create mode 100644 arch/x86/include/asm/unaccepted_memory.h
 create mode 100644 arch/x86/mm/unaccepted_memory.c

-- 
2.35.1

[PATCHv6 01/15] x86/boot: Centralize __pa()/__va() definitions

[Kirill A. Shutemov]

Replace multiple __pa()/__va() definitions with a single one in misc.h.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
---
 arch/x86/boot/compressed/ident_map_64.c | 8 --------
 arch/x86/boot/compressed/misc.h         | 9 +++++++++
 arch/x86/boot/compressed/sev.c          | 2 --
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
index 44c350d627c7..66a2e992c5f5 100644
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -8,14 +8,6 @@
  * Copyright (C)      2016  Kees Cook
  */
 
-/*
- * Since we're dealing with identity mappings, physical and virtual
- * addresses are the same, so override these defines which are ultimately
- * used by the headers in misc.h.
- */
-#define __pa(x)  ((unsigned long)(x))
-#define __va(x)  ((void *)((unsigned long)(x)))
-
 /* No PAGE_TABLE_ISOLATION support needed either: */
 #undef CONFIG_PAGE_TABLE_ISOLATION
 
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 4910bf230d7b..245cf8f2a0bd 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -19,6 +19,15 @@
 /* cpu_feature_enabled() cannot be used this early */
 #define USE_EARLY_PGTABLE_L5
 
+/*
+ * Boot stub deals with identity mappings, physical and virtual addresses are
+ * the same, so override these defines.
+ *
+ * <asm/page.h> will not define them if they are already defined.
+ */
+#define __pa(x)  ((unsigned long)(x))
+#define __va(x)  ((void *)((unsigned long)(x)))
+
 #include <linux/linkage.h>
 #include <linux/screen_info.h>
 #include <linux/elf.h>
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 52f989f6acc2..730c4677e9db 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -104,9 +104,7 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
 }
 
 #undef __init
-#undef __pa
 #define __init
-#define __pa(x)	((unsigned long)(x))
 
 #define __BOOT_COMPRESSED
 
-- 
2.35.1

[PATCHv6 02/15] mm: Add support for unaccepted memory

[Kirill A. Shutemov]

UEFI Specification version 2.9 introduces the concept of memory
acceptance. Some Virtual Machine platforms, such as Intel TDX or AMD
SEV-SNP, require memory to be accepted before it can be used by the
guest. Accepting happens via a protocol specific to the Virtual Machine
platform.

There are several ways kernel can deal with unaccepted memory:

 1. Accept all the memory during the boot. It is easy to implement and
    it doesn't have runtime cost once the system is booted. The downside
    is very long boot time.

    Accept can be parallelized to multiple CPUs to keep it manageable
    (i.e. via DEFERRED_STRUCT_PAGE_INIT), but it tends to saturate
    memory bandwidth and does not scale beyond the point.

 2. Accept a block of memory on the first use. It requires more
    infrastructure and changes in page allocator to make it work, but
    it provides good boot time.

    On-demand memory accept means latency spikes every time kernel steps
    onto a new memory block. The spikes will go away once workload data
    set size gets stabilized or all memory gets accepted.

 3. Accept all memory in background. Introduce a thread (or multiple)
    that gets memory accepted proactively. It will minimize time the
    system experience latency spikes on memory allocation while keeping
    low boot time.

    This approach cannot function on its own. It is an extension of #2:
    background memory acceptance requires functional scheduler, but the
    page allocator may need to tap into unaccepted memory before that.

    The downside of the approach is that these threads also steal CPU
    cycles and memory bandwidth from the user's workload and may hurt
    user experience.

Implement #2 for now. It is a reasonable default. Some workloads may
want to use #1 or #3 and they can be implemented later based on user's
demands.

Support of unaccepted memory requires a few changes in core-mm code:

  - memblock has to accept memory on allocation;

  - page allocator has to accept memory on the first allocation of the
    page;

Memblock change is trivial.

The page allocator is modified to accept pages on the first allocation.
The new page type (encoded in the _mapcount) -- PageUnaccepted() -- is
used to indicate that the page requires acceptance.

Architecture has to provide two helpers if it wants to support
unaccepted memory:

 - accept_memory() makes a range of physical addresses accepted.

 - memory_is_unaccepted() checks anything within the range of physical
   addresses requires acceptance.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>	# memblock
---
 include/linux/page-flags.h | 31 ++++++++++++++
 mm/internal.h              | 12 ++++++
 mm/memblock.c              |  9 ++++
 mm/page_alloc.c            | 87 +++++++++++++++++++++++++++++++++++++-
 4 files changed, 137 insertions(+), 2 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 9d8eeaa67d05..7f21267366a9 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -928,6 +928,14 @@ static inline bool is_page_hwpoison(struct page *page)
 #define PG_offline	0x00000100
 #define PG_table	0x00000200
 #define PG_guard	0x00000400
+#define PG_unaccepted	0x00000800
+
+/*
+ * Page types allowed at page_expected_state()
+ *
+ * PageUnaccepted() will get cleared in post_alloc_hook().
+ */
+#define PAGE_TYPES_EXPECTED	PG_unaccepted
 
 #define PageType(page, flag)						\
 	((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
@@ -953,6 +961,18 @@ static __always_inline void __ClearPage##uname(struct page *page)	\
 	page->page_type |= PG_##lname;					\
 }
 
+#define PAGE_TYPE_OPS_FALSE(uname)					\
+static __always_inline int Page##uname(struct page *page)		\
+{									\
+	return false;							\
+}									\
+static __always_inline void __SetPage##uname(struct page *page)		\
+{									\
+}									\
+static __always_inline void __ClearPage##uname(struct page *page)	\
+{									\
+}
+
 /*
  * PageBuddy() indicates that the page is free and in the buddy system
  * (see mm/page_alloc.c).
@@ -983,6 +1003,17 @@ PAGE_TYPE_OPS(Buddy, buddy)
  */
 PAGE_TYPE_OPS(Offline, offline)
 
+/*
+ * PageUnaccepted() indicates that the page has to be "accepted" before it can
+ * be read or written. The page allocator must call accept_page() before
+ * touching the page or returning it to the caller.
+ */
+#ifdef CONFIG_UNACCEPTED_MEMORY
+PAGE_TYPE_OPS(Unaccepted, unaccepted)
+#else
+PAGE_TYPE_OPS_FALSE(Unaccepted)
+#endif
+
 extern void page_offline_freeze(void);
 extern void page_offline_thaw(void);
 extern void page_offline_begin(void);
diff --git a/mm/internal.h b/mm/internal.h
index cf16280ce132..3fd5d8f90492 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -758,4 +758,16 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
 
 DECLARE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
 
+#ifndef CONFIG_UNACCEPTED_MEMORY
+static inline bool range_contains_unaccepted_memory(phys_addr_t start,
+						    phys_addr_t end)
+{
+	return false;
+}
+
+static inline void accept_memory(phys_addr_t start, phys_addr_t end)
+{
+}
+#endif
+
 #endif	/* __MM_INTERNAL_H */
diff --git a/mm/memblock.c b/mm/memblock.c
index e4f03a6e8e56..a1f7f8b304d5 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1405,6 +1405,15 @@ phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
 		 */
 		kmemleak_alloc_phys(found, size, 0, 0);
 
+	/*
+	 * Some Virtual Machine platforms, such as Intel TDX or AMD SEV-SNP,
+	 * require memory to be accepted before it can be used by the
+	 * guest.
+	 *
+	 * Accept the memory of the allocated buffer.
+	 */
+	accept_memory(found, found + size);
+
 	return found;
 }
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0e42038382c1..c8b6e29f4402 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -121,6 +121,12 @@ typedef int __bitwise fpi_t;
  */
 #define FPI_SKIP_KASAN_POISON	((__force fpi_t)BIT(2))
 
+/*
+ * Check if the page needs to be marked as PageUnaccepted().
+ * Used for the new pages added to the buddy allocator for the first time.
+ */
+#define FPI_UNACCEPTED_SLOWPATH	((__force fpi_t)BIT(3))
+
 /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
 static DEFINE_MUTEX(pcp_batch_high_lock);
 #define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
@@ -1023,6 +1029,32 @@ buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
 	return page_is_buddy(higher_page, higher_buddy, order + 1);
 }
 
+/*
+ * Page acceptance can be very slow. Do not call under critical locks.
+ */
+static void accept_page(struct page *page, unsigned int order)
+{
+	phys_addr_t start = page_to_phys(page);
+	int i;
+
+	accept_memory(start, start + (PAGE_SIZE << order));
+	__ClearPageUnaccepted(page);
+
+	/* Assert that there is no PageUnaccepted() on tail pages */
+	if (IS_ENABLED(CONFIG_DEBUG_VM)) {
+		for (i = 1; i < (1 << order); i++)
+			VM_BUG_ON_PAGE(PageUnaccepted(page + i), page + i);
+	}
+}
+
+static bool page_is_unaccepted(struct page *page, unsigned int order)
+{
+	phys_addr_t start = page_to_phys(page);
+	phys_addr_t end = start + (PAGE_SIZE << order);
+
+	return range_contains_unaccepted_memory(start, end);
+}
+
 /*
  * Freeing function for a buddy system allocator.
  *
@@ -1058,6 +1090,7 @@ static inline void __free_one_page(struct page *page,
 	unsigned long combined_pfn;
 	struct page *buddy;
 	bool to_tail;
+	bool page_needs_acceptance = false;
 
 	VM_BUG_ON(!zone_is_initialized(zone));
 	VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);
@@ -1069,6 +1102,11 @@ static inline void __free_one_page(struct page *page,
 	VM_BUG_ON_PAGE(pfn & ((1 << order) - 1), page);
 	VM_BUG_ON_PAGE(bad_range(zone, page), page);
 
+	if (PageUnaccepted(page)) {
+		page_needs_acceptance = true;
+		__ClearPageUnaccepted(page);
+	}
+
 continue_merging:
 	while (order < max_order) {
 		if (compaction_capture(capc, page, order, migratetype)) {
@@ -1089,6 +1127,13 @@ static inline void __free_one_page(struct page *page,
 			clear_page_guard(zone, buddy, order, migratetype);
 		else
 			del_page_from_free_list(buddy, zone, order);
+
+		/* Mark page unaccepted if any of merged pages were unaccepted */
+		if (PageUnaccepted(buddy)) {
+			page_needs_acceptance = true;
+			__ClearPageUnaccepted(buddy);
+		}
+
 		combined_pfn = buddy_pfn & pfn;
 		page = page + (combined_pfn - pfn);
 		pfn = combined_pfn;
@@ -1124,6 +1169,23 @@ static inline void __free_one_page(struct page *page,
 done_merging:
 	set_buddy_order(page, order);
 
+	/*
+	 * The page gets marked as PageUnaccepted() if any of merged-in pages
+	 * is PageUnaccepted().
+	 *
+	 * New pages, just being added to buddy allocator, do not have
+	 * PageUnaccepted() set. FPI_UNACCEPTED_SLOWPATH indicates that the
+	 * page is new and page_is_unaccepted() check is required to
+	 * determinate if acceptance is required.
+	 *
+	 * Avoid calling page_is_unaccepted() if it is known that the page
+	 * needs acceptance. It can be costly.
+	 */
+	if (!page_needs_acceptance && (fpi_flags & FPI_UNACCEPTED_SLOWPATH))
+		page_needs_acceptance = page_is_unaccepted(page, order);
+	if (page_needs_acceptance)
+		__SetPageUnaccepted(page);
+
 	if (fpi_flags & FPI_TO_TAIL)
 		to_tail = true;
 	else if (is_shuffle_order(order))
@@ -1149,7 +1211,13 @@ static inline void __free_one_page(struct page *page,
 static inline bool page_expected_state(struct page *page,
 					unsigned long check_flags)
 {
-	if (unlikely(atomic_read(&page->_mapcount) != -1))
+	/*
+	 * The page must not be mapped to userspace and must not have
+	 * a PageType other than listed in PAGE_TYPES_EXPECTED.
+	 *
+	 * Note, bit cleared means the page type is set.
+	 */
+	if (unlikely((atomic_read(&page->_mapcount) | PAGE_TYPES_EXPECTED) != -1))
 		return false;
 
 	if (unlikely((unsigned long)page->mapping |
@@ -1654,7 +1722,9 @@ void __free_pages_core(struct page *page, unsigned int order)
 	 * Bypass PCP and place fresh pages right to the tail, primarily
 	 * relevant for memory onlining.
 	 */
-	__free_pages_ok(page, order, FPI_TO_TAIL | FPI_SKIP_KASAN_POISON);
+	__free_pages_ok(page, order,
+			FPI_TO_TAIL | FPI_SKIP_KASAN_POISON |
+			FPI_UNACCEPTED_SLOWPATH);
 }
 
 #ifdef CONFIG_NUMA
@@ -1807,6 +1877,9 @@ static void __init deferred_free_range(unsigned long pfn,
 		return;
 	}
 
+	/* Accept chunks smaller than page-block upfront */
+	accept_memory(pfn << PAGE_SHIFT, (pfn + nr_pages) << PAGE_SHIFT);
+
 	for (i = 0; i < nr_pages; i++, page++, pfn++) {
 		if ((pfn & (pageblock_nr_pages - 1)) == 0)
 			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
@@ -2266,6 +2339,13 @@ static inline void expand(struct zone *zone, struct page *page,
 		if (set_page_guard(zone, &page[size], high, migratetype))
 			continue;
 
+		/*
+		 * Transfer PageUnaccepted() to the newly split pages so
+		 * they can be accepted after dropping the zone lock.
+		 */
+		if (PageUnaccepted(page))
+			__SetPageUnaccepted(&page[size]);
+
 		add_to_free_list(&page[size], zone, high, migratetype);
 		set_buddy_order(&page[size], high);
 	}
@@ -2396,6 +2476,9 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
 	 */
 	kernel_unpoison_pages(page, 1 << order);
 
+	if (PageUnaccepted(page))
+		accept_page(page, order);
+
 	/*
 	 * As memory initialization might be integrated into KASAN,
 	 * KASAN unpoisoning and memory initializion code must be
-- 
2.35.1

[PATCHv6 03/15] efi/x86: Get full memory map in allocate_e820()

[Kirill A. Shutemov]

Currently allocate_e820() only interested in the size of map and size of
memory descriptor to determine how many e820 entries the kernel needs.

UEFI Specification version 2.9 introduces a new memory type --
unaccepted memory. To track unaccepted memory kernel needs to allocate
a bitmap. The size of the bitmap is dependent on the maximum physical
address present in the system. A full memory map is required to find
the maximum address.

Modify allocate_e820() to get a full memory map.

This is preparation for the next patch that implements handling of
unaccepted memory in EFI stub.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 drivers/firmware/efi/libstub/x86-stub.c | 28 +++++++++++--------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 01ddd4502e28..252ee222ca1e 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -569,31 +569,27 @@ static efi_status_t alloc_e820ext(u32 nr_desc, struct setup_data **e820ext,
 }
 
 static efi_status_t allocate_e820(struct boot_params *params,
+				  struct efi_boot_memmap *map,
 				  struct setup_data **e820ext,
 				  u32 *e820ext_size)
 {
-	unsigned long map_size, desc_size, map_key;
 	efi_status_t status;
-	__u32 nr_desc, desc_version;
+	__u32 nr_desc;
 
-	/* Only need the size of the mem map and size of each mem descriptor */
-	map_size = 0;
-	status = efi_bs_call(get_memory_map, &map_size, NULL, &map_key,
-			     &desc_size, &desc_version);
-	if (status != EFI_BUFFER_TOO_SMALL)
-		return (status != EFI_SUCCESS) ? status : EFI_UNSUPPORTED;
-
-	nr_desc = map_size / desc_size + EFI_MMAP_NR_SLACK_SLOTS;
+	status = efi_get_memory_map(map);
+	if (status != EFI_SUCCESS)
+		return status;
 
-	if (nr_desc > ARRAY_SIZE(params->e820_table)) {
-		u32 nr_e820ext = nr_desc - ARRAY_SIZE(params->e820_table);
+	nr_desc = *map->map_size / *map->desc_size;
+	if (nr_desc > ARRAY_SIZE(params->e820_table) - EFI_MMAP_NR_SLACK_SLOTS) {
+		u32 nr_e820ext = nr_desc - ARRAY_SIZE(params->e820_table) +
+			EFI_MMAP_NR_SLACK_SLOTS;
 
 		status = alloc_e820ext(nr_e820ext, e820ext, e820ext_size);
-		if (status != EFI_SUCCESS)
-			return status;
 	}
 
-	return EFI_SUCCESS;
+	efi_bs_call(free_pool, *map->map);
+	return status;
 }
 
 struct exit_boot_struct {
@@ -642,7 +638,7 @@ static efi_status_t exit_boot(struct boot_params *boot_params, void *handle)
 	priv.boot_params	= boot_params;
 	priv.efi		= &boot_params->efi_info;
 
-	status = allocate_e820(boot_params, &e820ext, &e820ext_size);
+	status = allocate_e820(boot_params, &map, &e820ext, &e820ext_size);
 	if (status != EFI_SUCCESS)
 		return status;
 
-- 
2.35.1

[PATCHv6 04/15] x86/boot: Add infrastructure required for unaccepted memory support

[Kirill A. Shutemov]

Pull functionality from the main kernel headers and lib/ that is
required for unaccepted memory support.

This is preparatory patch. The users for the functionality will come in
following patches.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/boot/bitops.h                   | 40 ++++++++++++
 arch/x86/boot/compressed/align.h         | 14 +++++
 arch/x86/boot/compressed/bitmap.c        | 43 +++++++++++++
 arch/x86/boot/compressed/bitmap.h        | 49 +++++++++++++++
 arch/x86/boot/compressed/bits.h          | 36 +++++++++++
 arch/x86/boot/compressed/compiler.h      |  9 +++
 arch/x86/boot/compressed/find.c          | 54 ++++++++++++++++
 arch/x86/boot/compressed/find.h          | 80 ++++++++++++++++++++++++
 arch/x86/boot/compressed/math.h          | 37 +++++++++++
 arch/x86/boot/compressed/minmax.h        | 61 ++++++++++++++++++
 arch/x86/boot/compressed/pgtable_types.h | 25 ++++++++
 11 files changed, 448 insertions(+)
 create mode 100644 arch/x86/boot/compressed/align.h
 create mode 100644 arch/x86/boot/compressed/bitmap.c
 create mode 100644 arch/x86/boot/compressed/bitmap.h
 create mode 100644 arch/x86/boot/compressed/bits.h
 create mode 100644 arch/x86/boot/compressed/compiler.h
 create mode 100644 arch/x86/boot/compressed/find.c
 create mode 100644 arch/x86/boot/compressed/find.h
 create mode 100644 arch/x86/boot/compressed/math.h
 create mode 100644 arch/x86/boot/compressed/minmax.h
 create mode 100644 arch/x86/boot/compressed/pgtable_types.h

diff --git a/arch/x86/boot/bitops.h b/arch/x86/boot/bitops.h
index 02e1dea11d94..61eb820ee402 100644
--- a/arch/x86/boot/bitops.h
+++ b/arch/x86/boot/bitops.h
@@ -41,4 +41,44 @@ static inline void set_bit(int nr, void *addr)
 	asm("btsl %1,%0" : "+m" (*(u32 *)addr) : "Ir" (nr));
 }
 
+static __always_inline void __set_bit(long nr, volatile unsigned long *addr)
+{
+	asm volatile(__ASM_SIZE(bts) " %1,%0" : : "m" (*(volatile long *) addr),
+		     "Ir" (nr) : "memory");
+}
+
+static __always_inline void __clear_bit(long nr, volatile unsigned long *addr)
+{
+	asm volatile(__ASM_SIZE(btr) " %1,%0" : : "m" (*(volatile long *) addr),
+		     "Ir" (nr) : "memory");
+}
+
+/**
+ * __ffs - find first set bit in word
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+static __always_inline unsigned long __ffs(unsigned long word)
+{
+	asm("rep; bsf %1,%0"
+		: "=r" (word)
+		: "rm" (word));
+	return word;
+}
+
+/**
+ * ffz - find first zero bit in word
+ * @word: The word to search
+ *
+ * Undefined if no zero exists, so code should check against ~0UL first.
+ */
+static __always_inline unsigned long ffz(unsigned long word)
+{
+	asm("rep; bsf %1,%0"
+		: "=r" (word)
+		: "r" (~word));
+	return word;
+}
+
 #endif /* BOOT_BITOPS_H */
diff --git a/arch/x86/boot/compressed/align.h b/arch/x86/boot/compressed/align.h
new file mode 100644
index 000000000000..7ccabbc5d1b8
--- /dev/null
+++ b/arch/x86/boot/compressed/align.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef BOOT_ALIGN_H
+#define BOOT_ALIGN_H
+#define _LINUX_ALIGN_H /* Inhibit inclusion of <linux/align.h> */
+
+/* @a is a power of 2 value */
+#define ALIGN(x, a)		__ALIGN_KERNEL((x), (a))
+#define ALIGN_DOWN(x, a)	__ALIGN_KERNEL((x) - ((a) - 1), (a))
+#define __ALIGN_MASK(x, mask)	__ALIGN_KERNEL_MASK((x), (mask))
+#define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
+#define PTR_ALIGN_DOWN(p, a)	((typeof(p))ALIGN_DOWN((unsigned long)(p), (a)))
+#define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
+
+#endif
diff --git a/arch/x86/boot/compressed/bitmap.c b/arch/x86/boot/compressed/bitmap.c
new file mode 100644
index 000000000000..789ecadeb521
--- /dev/null
+++ b/arch/x86/boot/compressed/bitmap.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "bitmap.h"
+
+void __bitmap_set(unsigned long *map, unsigned int start, int len)
+{
+	unsigned long *p = map + BIT_WORD(start);
+	const unsigned int size = start + len;
+	int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
+	unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
+
+	while (len - bits_to_set >= 0) {
+		*p |= mask_to_set;
+		len -= bits_to_set;
+		bits_to_set = BITS_PER_LONG;
+		mask_to_set = ~0UL;
+		p++;
+	}
+	if (len) {
+		mask_to_set &= BITMAP_LAST_WORD_MASK(size);
+		*p |= mask_to_set;
+	}
+}
+
+void __bitmap_clear(unsigned long *map, unsigned int start, int len)
+{
+	unsigned long *p = map + BIT_WORD(start);
+	const unsigned int size = start + len;
+	int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
+	unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
+
+	while (len - bits_to_clear >= 0) {
+		*p &= ~mask_to_clear;
+		len -= bits_to_clear;
+		bits_to_clear = BITS_PER_LONG;
+		mask_to_clear = ~0UL;
+		p++;
+	}
+	if (len) {
+		mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
+		*p &= ~mask_to_clear;
+	}
+}
diff --git a/arch/x86/boot/compressed/bitmap.h b/arch/x86/boot/compressed/bitmap.h
new file mode 100644
index 000000000000..35357f5feda2
--- /dev/null
+++ b/arch/x86/boot/compressed/bitmap.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef BOOT_BITMAP_H
+#define BOOT_BITMAP_H
+#define __LINUX_BITMAP_H /* Inhibit inclusion of <linux/bitmap.h> */
+
+#include "../bitops.h"
+#include "../string.h"
+#include "align.h"
+
+#define BITMAP_MEM_ALIGNMENT 8
+#define BITMAP_MEM_MASK (BITMAP_MEM_ALIGNMENT - 1)
+
+#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
+#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
+
+#define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
+
+void __bitmap_set(unsigned long *map, unsigned int start, int len);
+void __bitmap_clear(unsigned long *map, unsigned int start, int len);
+
+static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
+		unsigned int nbits)
+{
+	if (__builtin_constant_p(nbits) && nbits == 1)
+		__set_bit(start, map);
+	else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
+		 IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
+		 __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
+		 IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
+		memset((char *)map + start / 8, 0xff, nbits / 8);
+	else
+		__bitmap_set(map, start, nbits);
+}
+
+static __always_inline void bitmap_clear(unsigned long *map, unsigned int start,
+		unsigned int nbits)
+{
+	if (__builtin_constant_p(nbits) && nbits == 1)
+		__clear_bit(start, map);
+	else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
+		 IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
+		 __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
+		 IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
+		memset((char *)map + start / 8, 0, nbits / 8);
+	else
+		__bitmap_clear(map, start, nbits);
+}
+
+#endif
diff --git a/arch/x86/boot/compressed/bits.h b/arch/x86/boot/compressed/bits.h
new file mode 100644
index 000000000000..b0ffa007ee19
--- /dev/null
+++ b/arch/x86/boot/compressed/bits.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef BOOT_BITS_H
+#define BOOT_BITS_H
+#define __LINUX_BITS_H /* Inhibit inclusion of <linux/bits.h> */
+
+#ifdef __ASSEMBLY__
+#define _AC(X,Y)	X
+#define _AT(T,X)	X
+#else
+#define __AC(X,Y)	(X##Y)
+#define _AC(X,Y)	__AC(X,Y)
+#define _AT(T,X)	((T)(X))
+#endif
+
+#define _UL(x)		(_AC(x, UL))
+#define _ULL(x)		(_AC(x, ULL))
+#define UL(x)		(_UL(x))
+#define ULL(x)		(_ULL(x))
+
+#define BIT(nr)			(UL(1) << (nr))
+#define BIT_ULL(nr)		(ULL(1) << (nr))
+#define BIT_MASK(nr)		(UL(1) << ((nr) % BITS_PER_LONG))
+#define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
+#define BIT_ULL_MASK(nr)	(ULL(1) << ((nr) % BITS_PER_LONG_LONG))
+#define BIT_ULL_WORD(nr)	((nr) / BITS_PER_LONG_LONG)
+#define BITS_PER_BYTE		8
+
+#define GENMASK(h, l) \
+	(((~UL(0)) - (UL(1) << (l)) + 1) & \
+	 (~UL(0) >> (BITS_PER_LONG - 1 - (h))))
+
+#define GENMASK_ULL(h, l) \
+	(((~ULL(0)) - (ULL(1) << (l)) + 1) & \
+	 (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))
+
+#endif
diff --git a/arch/x86/boot/compressed/compiler.h b/arch/x86/boot/compressed/compiler.h
new file mode 100644
index 000000000000..452c4c0844b9
--- /dev/null
+++ b/arch/x86/boot/compressed/compiler.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef BOOT_COMPILER_H
+#define BOOT_COMPILER_H
+#define __LINUX_COMPILER_H /* Inhibit inclusion of <linux/compiler.h> */
+
+# define likely(x)	__builtin_expect(!!(x), 1)
+# define unlikely(x)	__builtin_expect(!!(x), 0)
+
+#endif
diff --git a/arch/x86/boot/compressed/find.c b/arch/x86/boot/compressed/find.c
new file mode 100644
index 000000000000..839be91aae52
--- /dev/null
+++ b/arch/x86/boot/compressed/find.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include "bitmap.h"
+#include "find.h"
+#include "math.h"
+#include "minmax.h"
+
+static __always_inline unsigned long swab(const unsigned long y)
+{
+#if __BITS_PER_LONG == 64
+	return __builtin_bswap32(y);
+#else /* __BITS_PER_LONG == 32 */
+	return __builtin_bswap64(y);
+#endif
+}
+
+unsigned long _find_next_bit(const unsigned long *addr1,
+		const unsigned long *addr2, unsigned long nbits,
+		unsigned long start, unsigned long invert, unsigned long le)
+{
+	unsigned long tmp, mask;
+
+	if (unlikely(start >= nbits))
+		return nbits;
+
+	tmp = addr1[start / BITS_PER_LONG];
+	if (addr2)
+		tmp &= addr2[start / BITS_PER_LONG];
+	tmp ^= invert;
+
+	/* Handle 1st word. */
+	mask = BITMAP_FIRST_WORD_MASK(start);
+	if (le)
+		mask = swab(mask);
+
+	tmp &= mask;
+
+	start = round_down(start, BITS_PER_LONG);
+
+	while (!tmp) {
+		start += BITS_PER_LONG;
+		if (start >= nbits)
+			return nbits;
+
+		tmp = addr1[start / BITS_PER_LONG];
+		if (addr2)
+			tmp &= addr2[start / BITS_PER_LONG];
+		tmp ^= invert;
+	}
+
+	if (le)
+		tmp = swab(tmp);
+
+	return min(start + __ffs(tmp), nbits);
+}
diff --git a/arch/x86/boot/compressed/find.h b/arch/x86/boot/compressed/find.h
new file mode 100644
index 000000000000..799176972ebc
--- /dev/null
+++ b/arch/x86/boot/compressed/find.h
@@ -0,0 +1,80 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef BOOT_FIND_H
+#define BOOT_FIND_H
+#define __LINUX_FIND_H /* Inhibit inclusion of <linux/find.h> */
+
+#include "../bitops.h"
+#include "align.h"
+#include "bits.h"
+#include "compiler.h"
+
+unsigned long _find_next_bit(const unsigned long *addr1,
+		const unsigned long *addr2, unsigned long nbits,
+		unsigned long start, unsigned long invert, unsigned long le);
+
+/**
+ * find_next_bit - find the next set bit in a memory region
+ * @addr: The address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The bitmap size in bits
+ *
+ * Returns the bit number for the next set bit
+ * If no bits are set, returns @size.
+ */
+static inline
+unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
+			    unsigned long offset)
+{
+	if (small_const_nbits(size)) {
+		unsigned long val;
+
+		if (unlikely(offset >= size))
+			return size;
+
+		val = *addr & GENMASK(size - 1, offset);
+		return val ? __ffs(val) : size;
+	}
+
+	return _find_next_bit(addr, NULL, size, offset, 0UL, 0);
+}
+
+/**
+ * find_next_zero_bit - find the next cleared bit in a memory region
+ * @addr: The address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The bitmap size in bits
+ *
+ * Returns the bit number of the next zero bit
+ * If no bits are zero, returns @size.
+ */
+static inline
+unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
+				 unsigned long offset)
+{
+	if (small_const_nbits(size)) {
+		unsigned long val;
+
+		if (unlikely(offset >= size))
+			return size;
+
+		val = *addr | ~GENMASK(size - 1, offset);
+		return val == ~0UL ? size : ffz(val);
+	}
+
+	return _find_next_bit(addr, NULL, size, offset, ~0UL, 0);
+}
+
+/**
+ * for_each_set_bitrange_from - iterate over all set bit ranges [b; e)
+ * @b: bit offset of start of current bitrange (first set bit); must be initialized
+ * @e: bit offset of end of current bitrange (first unset bit)
+ * @addr: bitmap address to base the search on
+ * @size: bitmap size in number of bits
+ */
+#define for_each_set_bitrange_from(b, e, addr, size)		\
+	for ((b) = find_next_bit((addr), (size), (b)),		\
+	     (e) = find_next_zero_bit((addr), (size), (b) + 1);	\
+	     (b) < (size);					\
+	     (b) = find_next_bit((addr), (size), (e) + 1),	\
+	     (e) = find_next_zero_bit((addr), (size), (b) + 1))
+#endif
diff --git a/arch/x86/boot/compressed/math.h b/arch/x86/boot/compressed/math.h
new file mode 100644
index 000000000000..f7eede84bbc2
--- /dev/null
+++ b/arch/x86/boot/compressed/math.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef BOOT_MATH_H
+#define BOOT_MATH_H
+#define __LINUX_MATH_H /* Inhibit inclusion of <linux/math.h> */
+
+/*
+ *
+ * This looks more complex than it should be. But we need to
+ * get the type for the ~ right in round_down (it needs to be
+ * as wide as the result!), and we want to evaluate the macro
+ * arguments just once each.
+ */
+#define __round_mask(x, y) ((__typeof__(x))((y)-1))
+
+/**
+ * round_up - round up to next specified power of 2
+ * @x: the value to round
+ * @y: multiple to round up to (must be a power of 2)
+ *
+ * Rounds @x up to next multiple of @y (which must be a power of 2).
+ * To perform arbitrary rounding up, use roundup() below.
+ */
+#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
+
+/**
+ * round_down - round down to next specified power of 2
+ * @x: the value to round
+ * @y: multiple to round down to (must be a power of 2)
+ *
+ * Rounds @x down to next multiple of @y (which must be a power of 2).
+ * To perform arbitrary rounding down, use rounddown() below.
+ */
+#define round_down(x, y) ((x) & ~__round_mask(x, y))
+
+#define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
+
+#endif
diff --git a/arch/x86/boot/compressed/minmax.h b/arch/x86/boot/compressed/minmax.h
new file mode 100644
index 000000000000..4efd05673260
--- /dev/null
+++ b/arch/x86/boot/compressed/minmax.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef BOOT_MINMAX_H
+#define BOOT_MINMAX_H
+#define __LINUX_MINMAX_H /* Inhibit inclusion of <linux/minmax.h> */
+
+/*
+ * This returns a constant expression while determining if an argument is
+ * a constant expression, most importantly without evaluating the argument.
+ * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
+ */
+#define __is_constexpr(x) \
+	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+
+/*
+ * min()/max()/clamp() macros must accomplish three things:
+ *
+ * - avoid multiple evaluations of the arguments (so side-effects like
+ *   "x++" happen only once) when non-constant.
+ * - perform strict type-checking (to generate warnings instead of
+ *   nasty runtime surprises). See the "unnecessary" pointer comparison
+ *   in __typecheck().
+ * - retain result as a constant expressions when called with only
+ *   constant expressions (to avoid tripping VLA warnings in stack
+ *   allocation usage).
+ */
+#define __typecheck(x, y) \
+	(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
+
+#define __no_side_effects(x, y) \
+		(__is_constexpr(x) && __is_constexpr(y))
+
+#define __safe_cmp(x, y) \
+		(__typecheck(x, y) && __no_side_effects(x, y))
+
+#define __cmp(x, y, op)	((x) op (y) ? (x) : (y))
+
+#define __cmp_once(x, y, unique_x, unique_y, op) ({	\
+		typeof(x) unique_x = (x);		\
+		typeof(y) unique_y = (y);		\
+		__cmp(unique_x, unique_y, op); })
+
+#define __careful_cmp(x, y, op) \
+	__builtin_choose_expr(__safe_cmp(x, y), \
+		__cmp(x, y, op), \
+		__cmp_once(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y), op))
+
+/**
+ * min - return minimum of two values of the same or compatible types
+ * @x: first value
+ * @y: second value
+ */
+#define min(x, y)	__careful_cmp(x, y, <)
+
+/**
+ * max - return maximum of two values of the same or compatible types
+ * @x: first value
+ * @y: second value
+ */
+#define max(x, y)	__careful_cmp(x, y, >)
+
+#endif
diff --git a/arch/x86/boot/compressed/pgtable_types.h b/arch/x86/boot/compressed/pgtable_types.h
new file mode 100644
index 000000000000..8f1d87a69efc
--- /dev/null
+++ b/arch/x86/boot/compressed/pgtable_types.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BOOT_COMPRESSED_PGTABLE_TYPES_H
+#define BOOT_COMPRESSED_PGTABLE_TYPES_H
+#define _ASM_X86_PGTABLE_DEFS_H /* Inhibit inclusion of <asm/pgtable_types.h> */
+
+#define PAGE_SHIFT	12
+
+#ifdef CONFIG_X86_64
+#define PTE_SHIFT	9
+#elif defined CONFIG_X86_PAE
+#define PTE_SHIFT	9
+#else /* 2-level */
+#define PTE_SHIFT	10
+#endif
+
+enum pg_level {
+	PG_LEVEL_NONE,
+	PG_LEVEL_4K,
+	PG_LEVEL_2M,
+	PG_LEVEL_1G,
+	PG_LEVEL_512G,
+	PG_LEVEL_NUM
+};
+
+#endif
-- 
2.35.1

[PATCHv6 05/15] efi/x86: Implement support for unaccepted memory

[Kirill A. Shutemov]

UEFI Specification version 2.9 introduces the concept of memory
acceptance: Some Virtual Machine platforms, such as Intel TDX or AMD
SEV-SNP, requiring memory to be accepted before it can be used by the
guest. Accepting happens via a protocol specific for the Virtual
Machine platform.

Accepting memory is costly and it makes VMM allocate memory for the
accepted guest physical address range. It's better to postpone memory
acceptance until memory is needed. It lowers boot time and reduces
memory overhead.

The kernel needs to know what memory has been accepted. Firmware
communicates this information via memory map: a new memory type --
EFI_UNACCEPTED_MEMORY -- indicates such memory.

Range-based tracking works fine for firmware, but it gets bulky for
the kernel: e820 has to be modified on every page acceptance. It leads
to table fragmentation, but there's a limited number of entries in the
e820 table

Another option is to mark such memory as usable in e820 and track if the
range has been accepted in a bitmap. One bit in the bitmap represents
2MiB in the address space: one 4k page is enough to track 64GiB or
physical address space.

In the worst-case scenario -- a huge hole in the middle of the
address space -- It needs 256MiB to handle 4PiB of the address
space.

Any unaccepted memory that is not aligned to 2M gets accepted upfront.

The bitmap is allocated and constructed in the EFI stub and passed down
to the kernel via boot_params. allocate_e820() allocates the bitmap if
unaccepted memory is present, according to the maximum address in the
memory map.

The same boot_params.unaccepted_memory can be used to pass the bitmap
between two kernels on kexec, but the use-case is not yet implemented.

The implementation requires some basic helpers in boot stub. They
provided by linux/ includes in the main kernel image, but is not present
in boot stub. Create copy of required functionality in the boot stub.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 Documentation/x86/zero-page.rst          |  1 +
 arch/x86/boot/compressed/Makefile        |  1 +
 arch/x86/boot/compressed/mem.c           | 68 ++++++++++++++++++++++++
 arch/x86/include/asm/unaccepted_memory.h | 10 ++++
 arch/x86/include/uapi/asm/bootparam.h    |  2 +-
 drivers/firmware/efi/Kconfig             | 14 +++++
 drivers/firmware/efi/efi.c               |  1 +
 drivers/firmware/efi/libstub/x86-stub.c  | 68 ++++++++++++++++++++++++
 include/linux/efi.h                      |  3 +-
 9 files changed, 166 insertions(+), 2 deletions(-)
 create mode 100644 arch/x86/boot/compressed/mem.c
 create mode 100644 arch/x86/include/asm/unaccepted_memory.h

diff --git a/Documentation/x86/zero-page.rst b/Documentation/x86/zero-page.rst
index 45aa9cceb4f1..f21905e61ade 100644
--- a/Documentation/x86/zero-page.rst
+++ b/Documentation/x86/zero-page.rst
@@ -20,6 +20,7 @@ Offset/Size	Proto	Name			Meaning
 060/010		ALL	ist_info		Intel SpeedStep (IST) BIOS support information
 						(struct ist_info)
 070/008		ALL	acpi_rsdp_addr		Physical address of ACPI RSDP table
+078/008		ALL	unaccepted_memory	Bitmap of unaccepted memory (1bit == 2M)
 080/010		ALL	hd0_info		hd0 disk parameter, OBSOLETE!!
 090/010		ALL	hd1_info		hd1 disk parameter, OBSOLETE!!
 0A0/010		ALL	sys_desc_table		System description table (struct sys_desc_table),
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 19e1905dcbf6..67732478323f 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -102,6 +102,7 @@ endif
 
 vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
 vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o $(obj)/tdcall.o
+vmlinux-objs-$(CONFIG_UNACCEPTED_MEMORY) += $(obj)/bitmap.o $(obj)/mem.o
 
 vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o
 vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
new file mode 100644
index 000000000000..415df0d3bc81
--- /dev/null
+++ b/arch/x86/boot/compressed/mem.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "../cpuflags.h"
+#include "bitmap.h"
+#include "error.h"
+#include "math.h"
+
+#define PMD_SHIFT	21
+#define PMD_SIZE	(_AC(1, UL) << PMD_SHIFT)
+#define PMD_MASK	(~(PMD_SIZE - 1))
+
+static inline void __accept_memory(phys_addr_t start, phys_addr_t end)
+{
+	/* Platform-specific memory-acceptance call goes here */
+	error("Cannot accept memory");
+}
+
+/*
+ * The accepted memory bitmap only works at PMD_SIZE granularity. If a request
+ * comes in to mark memory as unaccepted which is not PMD_SIZE-aligned, simply
+ * accept the memory now since it can not be *marked* as unaccepted.
+ */
+void process_unaccepted_memory(struct boot_params *params, u64 start, u64 end)
+{
+	/*
+	 * Accept small regions that might not be able to be represented
+	 * in the bitmap.  This is a bit imprecise and may accept some
+	 * areas that could have been represented in the bitmap instead.
+	 *
+	 * Consider case like this:
+	 *
+	 * | 4k | 2044k |    2048k   |
+	 * ^ 0x0        ^ 2MB        ^ 4MB
+	 *
+	 * all memory in the range is unaccepted, except for the first 4k.
+	 * The second 2M can be represented in the bitmap, but kernel accept it
+	 * right away. The imprecision makes the code simpler by ensuring that
+	 * at least one bit will be set int the bitmap below.
+	 */
+	if (end - start < 2 * PMD_SIZE) {
+		__accept_memory(start, end);
+		return;
+	}
+
+	/*
+	 * No matter how the start and end are aligned, at least one unaccepted
+	 * PMD_SIZE area will remain.
+	 */
+
+	/* Immediately accept a <PMD_SIZE piece at the start: */
+	if (start & ~PMD_MASK) {
+		__accept_memory(start, round_up(start, PMD_SIZE));
+		start = round_up(start, PMD_SIZE);
+	}
+
+	/* Immediately accept a <PMD_SIZE piece at the end: */
+	if (end & ~PMD_MASK) {
+		__accept_memory(round_down(end, PMD_SIZE), end);
+		end = round_down(end, PMD_SIZE);
+	}
+
+	/*
+	 * 'start' and 'end' are now both PMD-aligned.
+	 * Record the range as being unaccepted:
+	 */
+	bitmap_set((unsigned long *)params->unaccepted_memory,
+		   start / PMD_SIZE, (end - start) / PMD_SIZE);
+}
diff --git a/arch/x86/include/asm/unaccepted_memory.h b/arch/x86/include/asm/unaccepted_memory.h
new file mode 100644
index 000000000000..df0736d32858
--- /dev/null
+++ b/arch/x86/include/asm/unaccepted_memory.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2020 Intel Corporation */
+#ifndef _ASM_X86_UNACCEPTED_MEMORY_H
+#define _ASM_X86_UNACCEPTED_MEMORY_H
+
+struct boot_params;
+
+void process_unaccepted_memory(struct boot_params *params, u64 start, u64 num);
+
+#endif
diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index bea5cdcdf532..c62f6ee4b6f0 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -180,7 +180,7 @@ struct boot_params {
 	__u64  tboot_addr;				/* 0x058 */
 	struct ist_info ist_info;			/* 0x060 */
 	__u64 acpi_rsdp_addr;				/* 0x070 */
-	__u8  _pad3[8];					/* 0x078 */
+	__u64 unaccepted_memory;			/* 0x078 */
 	__u8  hd0_info[16];	/* obsolete! */		/* 0x080 */
 	__u8  hd1_info[16];	/* obsolete! */		/* 0x090 */
 	struct sys_desc_table sys_desc_table; /* obsolete! */	/* 0x0a0 */
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 2c3dac5ecb36..80d0e802107f 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -243,6 +243,20 @@ config EFI_DISABLE_PCI_DMA
 	  options "efi=disable_early_pci_dma" or "efi=no_disable_early_pci_dma"
 	  may be used to override this option.
 
+config UNACCEPTED_MEMORY
+	bool
+	depends on EFI_STUB
+	help
+	   Some Virtual Machine platforms, such as Intel TDX, require
+	   some memory to be "accepted" by the guest before it can be used.
+	   This mechanism helps prevent malicious hosts from making changes
+	   to guest memory.
+
+	   UEFI specification v2.9 introduced EFI_UNACCEPTED_MEMORY memory type.
+
+	   This option adds support for unaccepted memory and makes such memory
+	   usable by the kernel.
+
 endmenu
 
 config EFI_EMBEDDED_FIRMWARE
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 5502e176d51b..2c055afb1b11 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -747,6 +747,7 @@ static __initdata char memory_type_name[][13] = {
 	"MMIO Port",
 	"PAL Code",
 	"Persistent",
+	"Unaccepted",
 };
 
 char * __init efi_md_typeattr_format(char *buf, size_t size,
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 252ee222ca1e..ec14a9a6436b 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -15,6 +15,7 @@
 #include <asm/setup.h>
 #include <asm/desc.h>
 #include <asm/boot.h>
+#include <asm/unaccepted_memory.h>
 
 #include "efistub.h"
 
@@ -504,6 +505,17 @@ setup_e820(struct boot_params *params, struct setup_data *e820ext, u32 e820ext_s
 			e820_type = E820_TYPE_PMEM;
 			break;
 
+		case EFI_UNACCEPTED_MEMORY:
+			if (!IS_ENABLED(CONFIG_UNACCEPTED_MEMORY)) {
+				efi_warn_once("The system has unaccepted memory,"
+					     " but kernel does not support it\n");
+				efi_warn_once("Consider enabling CONFIG_UNACCEPTED_MEMORY\n");
+				continue;
+			}
+			e820_type = E820_TYPE_RAM;
+			process_unaccepted_memory(params, d->phys_addr,
+						  d->phys_addr + PAGE_SIZE * d->num_pages);
+			break;
 		default:
 			continue;
 		}
@@ -568,6 +580,59 @@ static efi_status_t alloc_e820ext(u32 nr_desc, struct setup_data **e820ext,
 	return status;
 }
 
+static efi_status_t allocate_unaccepted_memory(struct boot_params *params,
+					       __u32 nr_desc,
+					       struct efi_boot_memmap *map)
+{
+	unsigned long *mem = NULL;
+	u64 size, max_addr = 0;
+	efi_status_t status;
+	bool found = false;
+	int i;
+
+	/* Check if there's any unaccepted memory and find the max address */
+	for (i = 0; i < nr_desc; i++) {
+		efi_memory_desc_t *d;
+
+		d = efi_early_memdesc_ptr(*map->map, *map->desc_size, i);
+		if (d->type == EFI_UNACCEPTED_MEMORY)
+			found = true;
+		if (d->phys_addr + d->num_pages * PAGE_SIZE > max_addr)
+			max_addr = d->phys_addr + d->num_pages * PAGE_SIZE;
+	}
+
+	if (!found) {
+		params->unaccepted_memory = 0;
+		return EFI_SUCCESS;
+	}
+
+	/*
+	 * If unaccepted memory is present allocate a bitmap to track what
+	 * memory has to be accepted before access.
+	 *
+	 * One bit in the bitmap represents 2MiB in the address space:
+	 * A 4k bitmap can track 64GiB of physical address space.
+	 *
+	 * In the worst case scenario -- a huge hole in the middle of the
+	 * address space -- It needs 256MiB to handle 4PiB of the address
+	 * space.
+	 *
+	 * TODO: handle situation if params->unaccepted_memory is already set.
+	 * It's required to deal with kexec.
+	 *
+	 * The bitmap will be populated in setup_e820() according to the memory
+	 * map after efi_exit_boot_services().
+	 */
+	size = DIV_ROUND_UP(max_addr, PMD_SIZE * BITS_PER_BYTE);
+	status = efi_allocate_pages(size, (unsigned long *)&mem, ULONG_MAX);
+	if (status == EFI_SUCCESS) {
+		memset(mem, 0, size);
+		params->unaccepted_memory = (unsigned long)mem;
+	}
+
+	return status;
+}
+
 static efi_status_t allocate_e820(struct boot_params *params,
 				  struct efi_boot_memmap *map,
 				  struct setup_data **e820ext,
@@ -588,6 +653,9 @@ static efi_status_t allocate_e820(struct boot_params *params,
 		status = alloc_e820ext(nr_e820ext, e820ext, e820ext_size);
 	}
 
+	if (IS_ENABLED(CONFIG_UNACCEPTED_MEMORY) && status == EFI_SUCCESS)
+		status = allocate_unaccepted_memory(params, nr_desc, map);
+
 	efi_bs_call(free_pool, *map->map);
 	return status;
 }
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 984aa688997a..8b03dc37bc29 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -108,7 +108,8 @@ typedef	struct {
 #define EFI_MEMORY_MAPPED_IO_PORT_SPACE	12
 #define EFI_PAL_CODE			13
 #define EFI_PERSISTENT_MEMORY		14
-#define EFI_MAX_MEMORY_TYPE		15
+#define EFI_UNACCEPTED_MEMORY		15
+#define EFI_MAX_MEMORY_TYPE		16
 
 /* Attribute values: */
 #define EFI_MEMORY_UC		((u64)0x0000000000000001ULL)	/* uncached */
-- 
2.35.1

[PATCHv6 06/15] x86/boot/compressed: Handle unaccepted memory

[Kirill A. Shutemov]

The firmware will pre-accept the memory used to run the stub. But, the
stub is responsible for accepting the memory into which it decompresses
the main kernel. Accept memory just before decompression starts.

The stub is also responsible for choosing a physical address in which to
place the decompressed kernel image. The KASLR mechanism will randomize
this physical address. Since the unaccepted memory region is relatively
small, KASLR would be quite ineffective if it only used the pre-accepted
area (EFI_CONVENTIONAL_MEMORY). Ensure that KASLR randomizes among the
entire physical address space by also including EFI_UNACCEPTED_MEMORY.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/boot/compressed/Makefile        |  2 +-
 arch/x86/boot/compressed/efi.h           |  1 +
 arch/x86/boot/compressed/kaslr.c         | 35 ++++++++++++++++--------
 arch/x86/boot/compressed/mem.c           | 18 ++++++++++++
 arch/x86/boot/compressed/misc.c          |  6 ++++
 arch/x86/boot/compressed/misc.h          |  6 ++++
 arch/x86/include/asm/unaccepted_memory.h |  2 ++
 7 files changed, 57 insertions(+), 13 deletions(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 67732478323f..85a631f5cdff 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -102,7 +102,7 @@ endif
 
 vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
 vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o $(obj)/tdcall.o
-vmlinux-objs-$(CONFIG_UNACCEPTED_MEMORY) += $(obj)/bitmap.o $(obj)/mem.o
+vmlinux-objs-$(CONFIG_UNACCEPTED_MEMORY) += $(obj)/bitmap.o $(obj)/find.o $(obj)/mem.o
 
 vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o
 vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
diff --git a/arch/x86/boot/compressed/efi.h b/arch/x86/boot/compressed/efi.h
index 7db2f41b54cd..cf475243b6d5 100644
--- a/arch/x86/boot/compressed/efi.h
+++ b/arch/x86/boot/compressed/efi.h
@@ -32,6 +32,7 @@ typedef	struct {
 } efi_table_hdr_t;
 
 #define EFI_CONVENTIONAL_MEMORY		 7
+#define EFI_UNACCEPTED_MEMORY		15
 
 #define EFI_MEMORY_MORE_RELIABLE \
 				((u64)0x0000000000010000ULL)	/* higher reliability */
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 4a3f223973f4..a42264b0b2f5 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -671,6 +671,28 @@ static bool process_mem_region(struct mem_vector *region,
 }
 
 #ifdef CONFIG_EFI
+
+/*
+ * Only EFI_CONVENTIONAL_MEMORY and EFI_UNACCEPTED_MEMORY (if supported) are
+ * guaranteed to be free.
+ *
+ * It is more conservative in picking free memory than the EFI spec allows:
+ *
+ * According to the spec, EFI_BOOT_SERVICES_{CODE|DATA} are also free memory
+ * and thus available to place the kernel image into, but in practice there's
+ * firmware where using that memory leads to crashes.
+ */
+static inline bool memory_type_is_free(efi_memory_desc_t *md)
+{
+	if (md->type == EFI_CONVENTIONAL_MEMORY)
+		return true;
+
+	if (md->type == EFI_UNACCEPTED_MEMORY)
+		return IS_ENABLED(CONFIG_UNACCEPTED_MEMORY);
+
+	return false;
+}
+
 /*
  * Returns true if we processed the EFI memmap, which we prefer over the E820
  * table if it is available.
@@ -715,18 +737,7 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
 	for (i = 0; i < nr_desc; i++) {
 		md = efi_early_memdesc_ptr(pmap, e->efi_memdesc_size, i);
 
-		/*
-		 * Here we are more conservative in picking free memory than
-		 * the EFI spec allows:
-		 *
-		 * According to the spec, EFI_BOOT_SERVICES_{CODE|DATA} are also
-		 * free memory and thus available to place the kernel image into,
-		 * but in practice there's firmware where using that memory leads
-		 * to crashes.
-		 *
-		 * Only EFI_CONVENTIONAL_MEMORY is guaranteed to be free.
-		 */
-		if (md->type != EFI_CONVENTIONAL_MEMORY)
+		if (!memory_type_is_free(md))
 			continue;
 
 		if (efi_soft_reserve_enabled() &&
diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
index 415df0d3bc81..b45458af00ca 100644
--- a/arch/x86/boot/compressed/mem.c
+++ b/arch/x86/boot/compressed/mem.c
@@ -3,12 +3,15 @@
 #include "../cpuflags.h"
 #include "bitmap.h"
 #include "error.h"
+#include "find.h"
 #include "math.h"
 
 #define PMD_SHIFT	21
 #define PMD_SIZE	(_AC(1, UL) << PMD_SHIFT)
 #define PMD_MASK	(~(PMD_SIZE - 1))
 
+extern struct boot_params *boot_params;
+
 static inline void __accept_memory(phys_addr_t start, phys_addr_t end)
 {
 	/* Platform-specific memory-acceptance call goes here */
@@ -66,3 +69,18 @@ void process_unaccepted_memory(struct boot_params *params, u64 start, u64 end)
 	bitmap_set((unsigned long *)params->unaccepted_memory,
 		   start / PMD_SIZE, (end - start) / PMD_SIZE);
 }
+
+void accept_memory(phys_addr_t start, phys_addr_t end)
+{
+	unsigned long range_start, range_end;
+	unsigned long *bitmap, bitmap_size;
+
+	bitmap = (unsigned long *)boot_params->unaccepted_memory;
+	range_start = start / PMD_SIZE;
+	bitmap_size = DIV_ROUND_UP(end, PMD_SIZE);
+
+	for_each_set_bitrange_from(range_start, range_end, bitmap, bitmap_size) {
+		__accept_memory(range_start * PMD_SIZE, range_end * PMD_SIZE);
+		bitmap_clear(bitmap, range_start, range_end - range_start);
+	}
+}
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index cf690d8712f4..c41a87b0ec06 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -454,6 +454,12 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 #endif
 
 	debug_putstr("\nDecompressing Linux... ");
+
+	if (boot_params->unaccepted_memory) {
+		debug_putstr("Accepting memory... ");
+		accept_memory(__pa(output), __pa(output) + needed_size);
+	}
+
 	__decompress(input_data, input_len, NULL, NULL, output, output_len,
 			NULL, error);
 	parse_elf(output);
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 245cf8f2a0bd..da7ef45133b9 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -235,4 +235,10 @@ static inline unsigned long efi_find_vendor_table(struct boot_params *bp,
 }
 #endif /* CONFIG_EFI */
 
+#ifdef CONFIG_UNACCEPTED_MEMORY
+void accept_memory(phys_addr_t start, phys_addr_t end);
+#else
+static inline void accept_memory(phys_addr_t start, phys_addr_t end) {}
+#endif
+
 #endif /* BOOT_COMPRESSED_MISC_H */
diff --git a/arch/x86/include/asm/unaccepted_memory.h b/arch/x86/include/asm/unaccepted_memory.h
index df0736d32858..41fbfc798100 100644
--- a/arch/x86/include/asm/unaccepted_memory.h
+++ b/arch/x86/include/asm/unaccepted_memory.h
@@ -7,4 +7,6 @@ struct boot_params;
 
 void process_unaccepted_memory(struct boot_params *params, u64 start, u64 num);
 
+void accept_memory(phys_addr_t start, phys_addr_t end);
+
 #endif
-- 
2.35.1

[PATCHv6 07/15] x86/mm: Reserve unaccepted memory bitmap

[Kirill A. Shutemov]

A given page of memory can only be accepted once. The kernel has to
accept memory both in the early decompression stage and during normal
runtime.

A bitmap is used to communicate the acceptance state of each page
between the decompression stage and normal runtime.

boot_params is used to communicate location of the bitmap throughout
the boot. The bitmap is allocated and initially populated in EFI stub.
Decompression stage accepts pages required for kernel/initrd and marks
these pages accordingly in the bitmap. The main kernel picks up the
bitmap from the same boot_params and uses it to determine what has to
be accepted on allocation.

In the runtime kernel, reserve the bitmap's memory to ensure nothing
overwrites it.

The size of bitmap is determined with e820__end_of_ram_pfn() which
relies on setup_e820() marking unaccepted memory as E820_TYPE_RAM.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
---
 arch/x86/kernel/e820.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index f267205f2d5a..22d1fe48dcba 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1316,6 +1316,16 @@ void __init e820__memblock_setup(void)
 	int i;
 	u64 end;
 
+	/* Mark unaccepted memory bitmap reserved */
+	if (boot_params.unaccepted_memory) {
+		unsigned long size;
+
+		/* One bit per 2MB */
+		size = DIV_ROUND_UP(e820__end_of_ram_pfn() * PAGE_SIZE,
+				    PMD_SIZE * BITS_PER_BYTE);
+		memblock_reserve(boot_params.unaccepted_memory, size);
+	}
+
 	/*
 	 * The bootstrap memblock region count maximum is 128 entries
 	 * (INIT_MEMBLOCK_REGIONS), but EFI might pass us more E820 entries
-- 
2.35.1

[PATCHv6 08/15] x86/mm: Provide helpers for unaccepted memory

[Kirill A. Shutemov]

Core-mm requires few helpers to support unaccepted memory:

 - accept_memory() checks the range of addresses against the bitmap and
   accept memory if needed.

 - memory_is_unaccepted() check if anything within the range requires
   acceptance.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/page.h              |  3 ++
 arch/x86/include/asm/unaccepted_memory.h |  4 ++
 arch/x86/mm/Makefile                     |  2 +
 arch/x86/mm/unaccepted_memory.c          | 56 ++++++++++++++++++++++++
 4 files changed, 65 insertions(+)
 create mode 100644 arch/x86/mm/unaccepted_memory.c

diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
index 9cc82f305f4b..df4ec3a988dc 100644
--- a/arch/x86/include/asm/page.h
+++ b/arch/x86/include/asm/page.h
@@ -19,6 +19,9 @@
 struct page;
 
 #include <linux/range.h>
+
+#include <asm/unaccepted_memory.h>
+
 extern struct range pfn_mapped[];
 extern int nr_pfn_mapped;
 
diff --git a/arch/x86/include/asm/unaccepted_memory.h b/arch/x86/include/asm/unaccepted_memory.h
index 41fbfc798100..89fc91c61560 100644
--- a/arch/x86/include/asm/unaccepted_memory.h
+++ b/arch/x86/include/asm/unaccepted_memory.h
@@ -7,6 +7,10 @@ struct boot_params;
 
 void process_unaccepted_memory(struct boot_params *params, u64 start, u64 num);
 
+#ifdef CONFIG_UNACCEPTED_MEMORY
+
 void accept_memory(phys_addr_t start, phys_addr_t end);
+bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end);
 
 #endif
+#endif
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index d957dc15b371..92438ad3d3b6 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -59,3 +59,5 @@ obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_amd.o
 
 obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_identity.o
 obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_boot.o
+
+obj-$(CONFIG_UNACCEPTED_MEMORY)	+= unaccepted_memory.o
diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
new file mode 100644
index 000000000000..0a86380b2478
--- /dev/null
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/memblock.h>
+#include <linux/mm.h>
+#include <linux/pfn.h>
+#include <linux/spinlock.h>
+
+#include <asm/io.h>
+#include <asm/setup.h>
+#include <asm/unaccepted_memory.h>
+
+/* Protects unaccepted memory bitmap */
+static DEFINE_SPINLOCK(unaccepted_memory_lock);
+
+void accept_memory(phys_addr_t start, phys_addr_t end)
+{
+	unsigned long range_start, range_end;
+	unsigned long *bitmap;
+	unsigned long flags;
+
+	if (!boot_params.unaccepted_memory)
+		return;
+
+	bitmap = __va(boot_params.unaccepted_memory);
+	range_start = start / PMD_SIZE;
+
+	spin_lock_irqsave(&unaccepted_memory_lock, flags);
+	for_each_set_bitrange_from(range_start, range_end, bitmap,
+				   DIV_ROUND_UP(end, PMD_SIZE)) {
+		unsigned long len = range_end - range_start;
+
+		/* Platform-specific memory-acceptance call goes here */
+		panic("Cannot accept memory: unknown platform\n");
+		bitmap_clear(bitmap, range_start, len);
+	}
+	spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
+}
+
+bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end)
+{
+	unsigned long *bitmap = __va(boot_params.unaccepted_memory);
+	unsigned long flags;
+	bool ret = false;
+
+	spin_lock_irqsave(&unaccepted_memory_lock, flags);
+	while (start < end) {
+		if (test_bit(start / PMD_SIZE, bitmap)) {
+			ret = true;
+			break;
+		}
+
+		start += PMD_SIZE;
+	}
+	spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
+
+	return ret;
+}
-- 
2.35.1

[PATCHv6 09/15] x86/mm: Avoid load_unaligned_zeropad() stepping into unaccepted memory

[Kirill A. Shutemov]

load_unaligned_zeropad() can lead to unwanted loads across page boundaries.
The unwanted loads are typically harmless. But, they might be made to
totally unrelated or even unmapped memory. load_unaligned_zeropad()
relies on exception fixup (#PF, #GP and now #VE) to recover from these
unwanted loads.

But, this approach does not work for unaccepted memory. For TDX, a load
from unaccepted memory will not lead to a recoverable exception within
the guest. The guest will exit to the VMM where the only recourse is to
terminate the guest.

There are three parts to fix this issue and comprehensively avoid access
to unaccepted memory. Together these ensure that an extra “guard” page
is accepted in addition to the memory that needs to be used.

1. Implicitly extend the memory_is_unaccepted(start, end) checks up to
   end+2M if ‘end’ is aligned on a 2M boundary.
2. Implicitly extend accept_memory(start, end) to end+2M if ‘end’ is
   aligned on a 2M boundary.
3. Set PageUnaccepted() on both memory that itself needs to be accepted
   *and* memory where the next page needs to be accepted. Essentially,
   make PageUnaccepted(page) a marker for whether work needs to be done
   to make ‘page’ usable. That work might include accepting pages in
   addition to ‘page’ itself.

Side note: This leads to something strange. Pages which were accepted
	   at boot, marked by the firmware as accepted and will never
	   _need_ to be accepted might have PageUnaccepted() set on
	   them. PageUnaccepted(page) is a cue to ensure that the next
	   page is accepted before ‘page’ can be used.

This is an actual, real-world problem which was discovered during TDX
testing.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/mm/unaccepted_memory.c         | 36 +++++++++++++++++++++++++
 drivers/firmware/efi/libstub/x86-stub.c |  7 +++++
 2 files changed, 43 insertions(+)

diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
index 0a86380b2478..33bf70592a46 100644
--- a/arch/x86/mm/unaccepted_memory.c
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -23,6 +23,38 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
 	bitmap = __va(boot_params.unaccepted_memory);
 	range_start = start / PMD_SIZE;
 
+	/*
+	 * load_unaligned_zeropad() can lead to unwanted loads across page
+	 * boundaries. The unwanted loads are typically harmless. But, they
+	 * might be made to totally unrelated or even unmapped memory.
+	 * load_unaligned_zeropad() relies on exception fixup (#PF, #GP and now
+	 * #VE) to recover from these unwanted loads.
+	 *
+	 * But, this approach does not work for unaccepted memory. For TDX, a
+	 * load from unaccepted memory will not lead to a recoverable exception
+	 * within the guest. The guest will exit to the VMM where the only
+	 * recourse is to terminate the guest.
+	 *
+	 * There are three parts to fix this issue and comprehensively avoid
+	 * access to unaccepted memory. Together these ensure that an extra
+	 * “guard” page is accepted in addition to the memory that needs to be
+	 * used:
+	 *
+	 * 1. Implicitly extend the range_contains_unaccepted_memory(start, end)
+	 *    checks up to end+2M if ‘end’ is aligned on a 2M boundary.
+	 *
+	 * 2. Implicitly extend accept_memory(start, end) to end+2M if ‘end’ is
+	 *    aligned on a 2M boundary.
+	 *
+	 * 3. Set PageUnaccepted() on both memory that itself needs to be
+	 *    accepted *and* memory where the next page needs to be accepted.
+	 *    Essentially, make PageUnaccepted(page) a marker for whether work
+	 *    needs to be done to make ‘page’ usable. That work might include
+	 *    accepting pages in addition to ‘page’ itself.
+	 */
+	if (!(end % PMD_SIZE))
+		end += PMD_SIZE;
+
 	spin_lock_irqsave(&unaccepted_memory_lock, flags);
 	for_each_set_bitrange_from(range_start, range_end, bitmap,
 				   DIV_ROUND_UP(end, PMD_SIZE)) {
@@ -41,6 +73,10 @@ bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end)
 	unsigned long flags;
 	bool ret = false;
 
+	/* See comment on load_unaligned_zeropad() in accept_memory() */
+	if (!(end % PMD_SIZE))
+		end += PMD_SIZE;
+
 	spin_lock_irqsave(&unaccepted_memory_lock, flags);
 	while (start < end) {
 		if (test_bit(start / PMD_SIZE, bitmap)) {
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index ec14a9a6436b..89705ae69cbf 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -606,6 +606,13 @@ static efi_status_t allocate_unaccepted_memory(struct boot_params *params,
 		return EFI_SUCCESS;
 	}
 
+	/*
+	 * range_contains_unaccepted_memory() may need to check one 2M chunk
+	 * beyond the end of RAM to deal with load_unaligned_zeropad(). Make
+	 * sure that the bitmap is large enough handle it.
+	 */
+	max_addr += PMD_SIZE;
+
 	/*
 	 * If unaccepted memory is present allocate a bitmap to track what
 	 * memory has to be accepted before access.
-- 
2.35.1

[PATCHv6 10/15] x86/mm: Report unaccepted memory in /proc/meminfo

[Kirill A. Shutemov]

Track amount of unaccepted memory and report it in /proc/meminfo.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/set_memory.h        |  2 ++
 arch/x86/include/asm/unaccepted_memory.h |  9 ++++++
 arch/x86/mm/init.c                       |  8 ++++++
 arch/x86/mm/pat/set_memory.c             |  2 +-
 arch/x86/mm/unaccepted_memory.c          | 36 +++++++++++++++++++++++-
 5 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
index 78ca53512486..e467f3941d22 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -86,6 +86,8 @@ bool kernel_page_present(struct page *page);
 
 extern int kernel_set_to_readonly;
 
+void direct_map_meminfo(struct seq_file *m);
+
 #ifdef CONFIG_X86_64
 /*
  * Prevent speculative access to the page by either unmapping
diff --git a/arch/x86/include/asm/unaccepted_memory.h b/arch/x86/include/asm/unaccepted_memory.h
index 89fc91c61560..d8622d952212 100644
--- a/arch/x86/include/asm/unaccepted_memory.h
+++ b/arch/x86/include/asm/unaccepted_memory.h
@@ -3,7 +3,10 @@
 #ifndef _ASM_X86_UNACCEPTED_MEMORY_H
 #define _ASM_X86_UNACCEPTED_MEMORY_H
 
+#include <linux/types.h>
+
 struct boot_params;
+struct seq_file;
 
 void process_unaccepted_memory(struct boot_params *params, u64 start, u64 num);
 
@@ -12,5 +15,11 @@ void process_unaccepted_memory(struct boot_params *params, u64 start, u64 num);
 void accept_memory(phys_addr_t start, phys_addr_t end);
 bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end);
 
+void unaccepted_meminfo(struct seq_file *m);
+
+#else
+
+static inline void unaccepted_meminfo(struct seq_file *m) {}
+
 #endif
 #endif
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index d8cfce221275..7e92a9d93994 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -1065,3 +1065,11 @@ unsigned long max_swapfile_size(void)
 	return pages;
 }
 #endif
+
+#ifdef CONFIG_PROC_FS
+void arch_report_meminfo(struct seq_file *m)
+{
+	direct_map_meminfo(m);
+	unaccepted_meminfo(m);
+}
+#endif
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 0656db33574d..f08881c4b8ee 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -105,7 +105,7 @@ static void split_page_count(int level)
 	direct_pages_count[level - 1] += PTRS_PER_PTE;
 }
 
-void arch_report_meminfo(struct seq_file *m)
+void direct_map_meminfo(struct seq_file *m)
 {
 	seq_printf(m, "DirectMap4k:    %8lu kB\n",
 			direct_pages_count[PG_LEVEL_4K] << 2);
diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
index 33bf70592a46..1ca71eb98c24 100644
--- a/arch/x86/mm/unaccepted_memory.c
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -2,14 +2,17 @@
 #include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/pfn.h>
+#include <linux/seq_file.h>
 #include <linux/spinlock.h>
 
+#include <asm/e820/api.h>
 #include <asm/io.h>
 #include <asm/setup.h>
 #include <asm/unaccepted_memory.h>
 
-/* Protects unaccepted memory bitmap */
+/* Protects unaccepted memory bitmap and nr_unaccepted */
 static DEFINE_SPINLOCK(unaccepted_memory_lock);
+static unsigned long nr_unaccepted;
 
 void accept_memory(phys_addr_t start, phys_addr_t end)
 {
@@ -63,6 +66,12 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
 		/* Platform-specific memory-acceptance call goes here */
 		panic("Cannot accept memory: unknown platform\n");
 		bitmap_clear(bitmap, range_start, len);
+
+		/* In early boot nr_unaccepted is not yet initialized */
+		if (nr_unaccepted) {
+			WARN_ON(nr_unaccepted < len);
+			nr_unaccepted -= len;
+		}
 	}
 	spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
 }
@@ -90,3 +99,28 @@ bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end)
 
 	return ret;
 }
+
+void unaccepted_meminfo(struct seq_file *m)
+{
+	seq_printf(m, "UnacceptedMem:  %8lu kB\n",
+		   (READ_ONCE(nr_unaccepted) * PMD_SIZE) >> 10);
+}
+
+static int __init unaccepted_init(void)
+{
+	unsigned long *unaccepted_memory;
+	unsigned long flags, bitmap_size;
+
+	if (!boot_params.unaccepted_memory)
+		return 0;
+
+	bitmap_size = e820__end_of_ram_pfn() * PAGE_SIZE / PMD_SIZE;
+	unaccepted_memory = __va(boot_params.unaccepted_memory);
+
+	spin_lock_irqsave(&unaccepted_memory_lock, flags);
+	nr_unaccepted = bitmap_weight(unaccepted_memory, bitmap_size);
+	spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
+
+	return 0;
+}
+fs_initcall(unaccepted_init);
-- 
2.35.1

[PATCHv6 11/15] x86: Disable kexec if system has unaccepted memory

[Kirill A. Shutemov]

On kexec, the target kernel has to know what memory has been accepted.
Information in EFI map is out of date and cannot be used.

boot_params.unaccepted_memory can be used to pass the bitmap between two
kernels on kexec, but the use-case is not yet implemented.

Disable kexec on machines with unaccepted memory for now.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/mm/unaccepted_memory.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
index 1ca71eb98c24..b4c43e6089b0 100644
--- a/arch/x86/mm/unaccepted_memory.c
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kexec.h>
 #include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/pfn.h>
@@ -114,6 +115,15 @@ static int __init unaccepted_init(void)
 	if (!boot_params.unaccepted_memory)
 		return 0;
 
+#ifdef CONFIG_KEXEC_CORE
+	/*
+	 * TODO: Information on memory acceptance status has to be communicated
+	 * between kernel.
+	 */
+	pr_warn("Disable kexec: not yet supported on systems with unaccepted memory\n");
+	kexec_load_disabled = 1;
+#endif
+
 	bitmap_size = e820__end_of_ram_pfn() * PAGE_SIZE / PMD_SIZE;
 	unaccepted_memory = __va(boot_params.unaccepted_memory);
 
-- 
2.35.1

[PATCHv6 12/15] x86/tdx: Make _tdx_hypercall() and __tdx_module_call() available in boot stub

[Kirill A. Shutemov]

Memory acceptance requires a hypercall and one or multiple module calls.

Make helpers for the calls available in boot stub. It has to accept
memory where kernel image and initrd are placed.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/coco/tdx/tdx.c           | 26 ------------------
 arch/x86/include/asm/shared/tdx.h | 45 +++++++++++++++++++++++++++++++
 arch/x86/include/asm/tdx.h        | 19 -------------
 3 files changed, 45 insertions(+), 45 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 5fbdda2f2b86..6a62d3950619 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -14,14 +14,6 @@
 #include <asm/trapnr.h>
 #include <asm/extable.h>
 
-/* TDX module Call Leaf IDs */
-#define TDX_GET_INFO			1
-#define TDX_GET_VEINFO			3
-#define TDX_ACCEPT_PAGE			6
-
-/* TDX hypercall Leaf IDs */
-#define TDVMCALL_MAP_GPA		0x10001
-
 /* MMIO direction */
 #define EPT_READ	0
 #define EPT_WRITE	1
@@ -36,24 +28,6 @@
 #define VE_GET_PORT_NUM(e)	((e) >> 16)
 #define VE_IS_IO_STRING(e)	((e) & BIT(4))
 
-/*
- * Wrapper for standard use of __tdx_hypercall with no output aside from
- * return code.
- */
-static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15)
-{
-	struct tdx_hypercall_args args = {
-		.r10 = TDX_HYPERCALL_STANDARD,
-		.r11 = fn,
-		.r12 = r12,
-		.r13 = r13,
-		.r14 = r14,
-		.r15 = r15,
-	};
-
-	return __tdx_hypercall(&args, 0);
-}
-
 /* Called from __tdx_hypercall() for unrecoverable failure */
 void __tdx_hypercall_failed(void)
 {
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index e53f26228fbb..956ced04c3be 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -13,6 +13,14 @@
 #define TDX_CPUID_LEAF_ID	0x21
 #define TDX_IDENT		"IntelTDX    "
 
+/* TDX module Call Leaf IDs */
+#define TDX_GET_INFO			1
+#define TDX_GET_VEINFO			3
+#define TDX_ACCEPT_PAGE			6
+
+/* TDX hypercall Leaf IDs */
+#define TDVMCALL_MAP_GPA		0x10001
+
 #ifndef __ASSEMBLY__
 
 /*
@@ -33,8 +41,45 @@ struct tdx_hypercall_args {
 /* Used to request services from the VMM */
 u64 __tdx_hypercall(struct tdx_hypercall_args *args, unsigned long flags);
 
+/*
+ * Wrapper for standard use of __tdx_hypercall with no output aside from
+ * return code.
+ */
+static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15)
+{
+	struct tdx_hypercall_args args = {
+		.r10 = TDX_HYPERCALL_STANDARD,
+		.r11 = fn,
+		.r12 = r12,
+		.r13 = r13,
+		.r14 = r14,
+		.r15 = r15,
+	};
+
+	return __tdx_hypercall(&args, 0);
+}
+
+
 /* Called from __tdx_hypercall() for unrecoverable failure */
 void __tdx_hypercall_failed(void);
 
+/*
+ * Used in __tdx_module_call() to gather the output registers' values of the
+ * TDCALL instruction when requesting services from the TDX module. This is a
+ * software only structure and not part of the TDX module/VMM ABI
+ */
+struct tdx_module_output {
+	u64 rcx;
+	u64 rdx;
+	u64 r8;
+	u64 r9;
+	u64 r10;
+	u64 r11;
+};
+
+/* Used to communicate with the TDX module */
+u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
+		      struct tdx_module_output *out);
+
 #endif /* !__ASSEMBLY__ */
 #endif /* _ASM_X86_SHARED_TDX_H */
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 020c81a7c729..d9106d3e89f8 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -20,21 +20,6 @@
 
 #ifndef __ASSEMBLY__
 
-/*
- * Used to gather the output registers values of the TDCALL and SEAMCALL
- * instructions when requesting services from the TDX module.
- *
- * This is a software only structure and not part of the TDX module/VMM ABI.
- */
-struct tdx_module_output {
-	u64 rcx;
-	u64 rdx;
-	u64 r8;
-	u64 r9;
-	u64 r10;
-	u64 r11;
-};
-
 /*
  * Used by the #VE exception handler to gather the #VE exception
  * info from the TDX module. This is a software only structure
@@ -55,10 +40,6 @@ struct ve_info {
 
 void __init tdx_early_init(void);
 
-/* Used to communicate with the TDX module */
-u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
-		      struct tdx_module_output *out);
-
 void tdx_get_ve_info(struct ve_info *ve);
 
 bool tdx_handle_virt_exception(struct pt_regs *regs, struct ve_info *ve);
-- 
2.35.1

[PATCHv6 13/15] x86/tdx: Refactor try_accept_one()

[Kirill A. Shutemov]

Rework try_accept_one() to return accepted size instead of modifying
'start' inside the helper. It makes 'start' in-only argumaent and
streamlines code on the caller side.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Suggested-by: Borislav Petkov <bp@alien8.de>
---
 arch/x86/coco/tdx/tdx.c | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 6a62d3950619..90237700a942 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -561,18 +561,18 @@ static bool tdx_cache_flush_required(void)
 	return true;
 }
 
-static bool try_accept_one(phys_addr_t *start, unsigned long len,
-			  enum pg_level pg_level)
+static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
+				    enum pg_level pg_level)
 {
 	unsigned long accept_size = page_level_size(pg_level);
 	u64 tdcall_rcx;
 	u8 page_size;
 
-	if (!IS_ALIGNED(*start, accept_size))
-		return false;
+	if (!IS_ALIGNED(start, accept_size))
+		return 0;
 
 	if (len < accept_size)
-		return false;
+		return 0;
 
 	/*
 	 * Pass the page physical address to the TDX module to accept the
@@ -591,15 +591,14 @@ static bool try_accept_one(phys_addr_t *start, unsigned long len,
 		page_size = 2;
 		break;
 	default:
-		return false;
+		return 0;
 	}
 
-	tdcall_rcx = *start | page_size;
+	tdcall_rcx = start | page_size;
 	if (__tdx_module_call(TDX_ACCEPT_PAGE, tdcall_rcx, 0, 0, 0, NULL))
-		return false;
+		return 0;
 
-	*start += accept_size;
-	return true;
+	return accept_size;
 }
 
 /*
@@ -636,21 +635,22 @@ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
 	 */
 	while (start < end) {
 		unsigned long len = end - start;
+		unsigned long accept_size;
 
 		/*
 		 * Try larger accepts first. It gives chance to VMM to keep
-		 * 1G/2M SEPT entries where possible and speeds up process by
-		 * cutting number of hypercalls (if successful).
+		 * 1G/2M Secure EPT entries where possible and speeds up
+		 * process by cutting number of hypercalls (if successful).
 		 */
 
-		if (try_accept_one(&start, len, PG_LEVEL_1G))
-			continue;
-
-		if (try_accept_one(&start, len, PG_LEVEL_2M))
-			continue;
-
-		if (!try_accept_one(&start, len, PG_LEVEL_4K))
+		accept_size = try_accept_one(start, len, PG_LEVEL_1G);
+		if (!accept_size)
+			accept_size = try_accept_one(start, len, PG_LEVEL_2M);
+		if (!accept_size)
+			accept_size = try_accept_one(start, len, PG_LEVEL_4K);
+		if (!accept_size)
 			return false;
+		start += accept_size;
 	}
 
 	return true;
-- 
2.35.1

[PATCHv6 14/15] x86/tdx: Add unaccepted memory support

[Kirill A. Shutemov]

Hookup TDX-specific code to accept memory.

Accepting the memory is the same process as converting memory from
shared to private: kernel notifies VMM with MAP_GPA hypercall and then
accept pages with ACCEPT_PAGE module call.

The implementation in core kernel uses tdx_enc_status_changed(). It
already used for converting memory to shared and back for I/O
transactions.

Boot stub provides own implementation of tdx_accept_memory(). It is
similar in structure to tdx_enc_status_changed(), but only cares about
converting memory to private.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/Kconfig                  |  1 +
 arch/x86/boot/compressed/mem.c    | 27 ++++++++++-
 arch/x86/boot/compressed/tdx.c    | 78 +++++++++++++++++++++++++++++++
 arch/x86/coco/tdx/tdx.c           | 30 ++++++++----
 arch/x86/include/asm/shared/tdx.h |  2 +
 arch/x86/mm/unaccepted_memory.c   |  9 +++-
 6 files changed, 136 insertions(+), 11 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f1320d9a3da3..661392f046ec 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -890,6 +890,7 @@ config INTEL_TDX_GUEST
 	select ARCH_HAS_CC_PLATFORM
 	select X86_MEM_ENCRYPT
 	select X86_MCE
+	select UNACCEPTED_MEMORY
 	help
 	  Support running as a guest under Intel TDX.  Without this support,
 	  the guest kernel can not boot or run under TDX.
diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
index b45458af00ca..48e36e640da1 100644
--- a/arch/x86/boot/compressed/mem.c
+++ b/arch/x86/boot/compressed/mem.c
@@ -5,6 +5,8 @@
 #include "error.h"
 #include "find.h"
 #include "math.h"
+#include "tdx.h"
+#include <asm/shared/tdx.h>
 
 #define PMD_SHIFT	21
 #define PMD_SIZE	(_AC(1, UL) << PMD_SHIFT)
@@ -12,10 +14,33 @@
 
 extern struct boot_params *boot_params;
 
+static bool is_tdx_guest(void)
+{
+	static bool once;
+	static bool is_tdx;
+
+	if (!IS_ENABLED(CONFIG_INTEL_TDX_GUEST))
+		return false;
+
+	if (!once) {
+		u32 eax, sig[3];
+
+		cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax,
+			    &sig[0], &sig[2],  &sig[1]);
+		is_tdx = !memcmp(TDX_IDENT, sig, sizeof(sig));
+		once = true;
+	}
+
+	return is_tdx;
+}
+
 static inline void __accept_memory(phys_addr_t start, phys_addr_t end)
 {
 	/* Platform-specific memory-acceptance call goes here */
-	error("Cannot accept memory");
+	if (is_tdx_guest())
+		tdx_accept_memory(start, end);
+	else
+		error("Cannot accept memory: unknown platform\n");
 }
 
 /*
diff --git a/arch/x86/boot/compressed/tdx.c b/arch/x86/boot/compressed/tdx.c
index 918a7606f53c..8518a75e5dd5 100644
--- a/arch/x86/boot/compressed/tdx.c
+++ b/arch/x86/boot/compressed/tdx.c
@@ -3,12 +3,15 @@
 #include "../cpuflags.h"
 #include "../string.h"
 #include "../io.h"
+#include "align.h"
 #include "error.h"
+#include "pgtable_types.h"
 
 #include <vdso/limits.h>
 #include <uapi/asm/vmx.h>
 
 #include <asm/shared/tdx.h>
+#include <asm/page_types.h>
 
 /* Called from __tdx_hypercall() for unrecoverable failure */
 void __tdx_hypercall_failed(void)
@@ -75,3 +78,78 @@ void early_tdx_detect(void)
 	pio_ops.f_outb = tdx_outb;
 	pio_ops.f_outw = tdx_outw;
 }
+
+static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
+				    enum pg_level level)
+{
+	unsigned long accept_size = PAGE_SIZE << ((level - 1) * PTE_SHIFT);
+	u64 tdcall_rcx;
+	u8 page_size;
+
+	if (!IS_ALIGNED(start, accept_size))
+		return 0;
+
+	if (len < accept_size)
+		return 0;
+
+	/*
+	 * Pass the page physical address to the TDX module to accept the
+	 * pending, private page.
+	 *
+	 * Bits 2:0 of RCX encode page size: 0 - 4K, 1 - 2M, 2 - 1G.
+	 */
+	switch (level) {
+	case PG_LEVEL_4K:
+		page_size = 0;
+		break;
+	case PG_LEVEL_2M:
+		page_size = 1;
+		break;
+	case PG_LEVEL_1G:
+		page_size = 2;
+		break;
+	default:
+		return 0;
+	}
+
+	tdcall_rcx = start | page_size;
+	if (__tdx_module_call(TDX_ACCEPT_PAGE, tdcall_rcx, 0, 0, 0, NULL))
+		return 0;
+
+	return accept_size;
+}
+
+void tdx_accept_memory(phys_addr_t start, phys_addr_t end)
+{
+	/*
+	 * Notify the VMM about page mapping conversion. More info about ABI
+	 * can be found in TDX Guest-Host-Communication Interface (GHCI),
+	 * section "TDG.VP.VMCALL<MapGPA>"
+	 */
+	if (_tdx_hypercall(TDVMCALL_MAP_GPA, start, end - start, 0, 0))
+		error("Accepting memory failed\n");
+
+	/*
+	 * For shared->private conversion, accept the page using
+	 * TDX_ACCEPT_PAGE TDX module call.
+	 */
+	while (start < end) {
+		unsigned long len = end - start;
+		unsigned long accept_size;
+
+		/*
+		 * Try larger accepts first. It gives chance to VMM to keep
+		 * 1G/2M Secure EPT entries where possible and speeds up
+		 * process by cutting number of hypercalls (if successful).
+		 */
+
+		accept_size = try_accept_one(start, len, PG_LEVEL_1G);
+		if (!accept_size)
+			accept_size = try_accept_one(start, len, PG_LEVEL_2M);
+		if (!accept_size)
+			accept_size = try_accept_one(start, len, PG_LEVEL_4K);
+		if (!accept_size)
+			error("Accepting memory failed\n");
+		start += accept_size;
+	}
+}
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 90237700a942..8649e6fe6c3a 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -601,16 +601,9 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
 	return accept_size;
 }
 
-/*
- * Inform the VMM of the guest's intent for this physical page: shared with
- * the VMM or private to the guest.  The VMM is expected to change its mapping
- * of the page in response.
- */
-static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
+static bool tdx_enc_status_changed_phys(phys_addr_t start, phys_addr_t end,
+					bool enc)
 {
-	phys_addr_t start = __pa(vaddr);
-	phys_addr_t end   = __pa(vaddr + numpages * PAGE_SIZE);
-
 	if (!enc) {
 		/* Set the shared (decrypted) bits: */
 		start |= cc_mkdec(0);
@@ -656,6 +649,25 @@ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
 	return true;
 }
 
+void tdx_accept_memory(phys_addr_t start, phys_addr_t end)
+{
+	if (!tdx_enc_status_changed_phys(start, end, true))
+		panic("Accepting memory failed: %#llx-%#llx\n",  start, end);
+}
+
+/*
+ * Inform the VMM of the guest's intent for this physical page: shared with
+ * the VMM or private to the guest.  The VMM is expected to change its mapping
+ * of the page in response.
+ */
+static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
+{
+	phys_addr_t start = __pa(vaddr);
+	phys_addr_t end = __pa(vaddr + numpages * PAGE_SIZE);
+
+	return tdx_enc_status_changed_phys(start, end, enc);
+}
+
 void __init tdx_early_init(void)
 {
 	u64 cc_mask;
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 956ced04c3be..97534c334473 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -81,5 +81,7 @@ struct tdx_module_output {
 u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
 		      struct tdx_module_output *out);
 
+void tdx_accept_memory(phys_addr_t start, phys_addr_t end);
+
 #endif /* !__ASSEMBLY__ */
 #endif /* _ASM_X86_SHARED_TDX_H */
diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
index b4c43e6089b0..6ecd79101922 100644
--- a/arch/x86/mm/unaccepted_memory.c
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -9,6 +9,7 @@
 #include <asm/e820/api.h>
 #include <asm/io.h>
 #include <asm/setup.h>
+#include <asm/shared/tdx.h>
 #include <asm/unaccepted_memory.h>
 
 /* Protects unaccepted memory bitmap and nr_unaccepted */
@@ -65,7 +66,13 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
 		unsigned long len = range_end - range_start;
 
 		/* Platform-specific memory-acceptance call goes here */
-		panic("Cannot accept memory: unknown platform\n");
+		if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
+			tdx_accept_memory(range_start * PMD_SIZE,
+					  range_end * PMD_SIZE);
+		} else {
+			panic("Cannot accept memory: unknown platform\n");
+		}
+
 		bitmap_clear(bitmap, range_start, len);
 
 		/* In early boot nr_unaccepted is not yet initialized */
-- 
2.35.1

[PATCHv6 15/15] mm/vmstat: Add counter for memory accepting

[Kirill A. Shutemov]

The counter increased every time kernel accepts a memory region.

The counter allows to see if memory acceptation is still ongoing and
contributes to memory allocation latency.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/mm/unaccepted_memory.c | 1 +
 include/linux/vm_event_item.h   | 3 +++
 mm/vmstat.c                     | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
index 6ecd79101922..fe1dabfae326 100644
--- a/arch/x86/mm/unaccepted_memory.c
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -74,6 +74,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
 		}
 
 		bitmap_clear(bitmap, range_start, len);
+		count_vm_events(ACCEPT_MEMORY, len * PMD_SIZE / PAGE_SIZE);
 
 		/* In early boot nr_unaccepted is not yet initialized */
 		if (nr_unaccepted) {
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 16a0a4fd000b..6a468164a2f9 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -136,6 +136,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 #ifdef CONFIG_X86
 		DIRECT_MAP_LEVEL2_SPLIT,
 		DIRECT_MAP_LEVEL3_SPLIT,
+#endif
+#ifdef CONFIG_UNACCEPTED_MEMORY
+		ACCEPT_MEMORY,
 #endif
 		NR_VM_EVENT_ITEMS
 };
diff --git a/mm/vmstat.c b/mm/vmstat.c
index b75b1a64b54c..4c9197f32406 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1397,6 +1397,9 @@ const char * const vmstat_text[] = {
 	"direct_map_level2_splits",
 	"direct_map_level3_splits",
 #endif
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	"accept_memory",
+#endif
 #endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
 };
 #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA || CONFIG_MEMCG */
-- 
2.35.1

Re: [PATCHv6 02/15] mm: Add support for unaccepted memory

[Andrew Morton]

On Tue, 17 May 2022 18:34:31 +0300 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> wrote:

> UEFI Specification version 2.9 introduces the concept of memory
> acceptance. Some Virtual Machine platforms, such as Intel TDX or AMD
> SEV-SNP, require memory to be accepted before it can be used by the
> guest. Accepting happens via a protocol specific to the Virtual Machine
> platform.
> 
> ...
>
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -928,6 +928,14 @@ static inline bool is_page_hwpoison(struct page *page)
>  #define PG_offline	0x00000100
>  #define PG_table	0x00000200
>  #define PG_guard	0x00000400
> +#define PG_unaccepted	0x00000800

"For pages that are never mapped to userspace (and aren't PageSlab),
page_type may be used."

Is that true of these pages?

Re: [PATCHv6 02/15] mm: Add support for unaccepted memory

[Kirill A. Shutemov]

On Tue, May 17, 2022 at 10:45:16AM -0700, Andrew Morton wrote:
> On Tue, 17 May 2022 18:34:31 +0300 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> wrote:
> 
> > UEFI Specification version 2.9 introduces the concept of memory
> > acceptance. Some Virtual Machine platforms, such as Intel TDX or AMD
> > SEV-SNP, require memory to be accepted before it can be used by the
> > guest. Accepting happens via a protocol specific to the Virtual Machine
> > platform.
> > 
> > ...
> >
> > --- a/include/linux/page-flags.h
> > +++ b/include/linux/page-flags.h
> > @@ -928,6 +928,14 @@ static inline bool is_page_hwpoison(struct page *page)
> >  #define PG_offline	0x00000100
> >  #define PG_table	0x00000200
> >  #define PG_guard	0x00000400
> > +#define PG_unaccepted	0x00000800
> 
> "For pages that are never mapped to userspace (and aren't PageSlab),
> page_type may be used."
> 
> Is that true of these pages?

Yes. PG_unaccepted is never set for any allocated page. It is only set for
pages on free lists. It gets cleared in post_alloc_hook().

-- 
 Kirill A. Shutemov

Re: [PATCHv6 02/15] mm: Add support for unaccepted memory

[Gupta, Pankaj]

Hi Kirill,

Thank you for your patch series.

I am trying to catch up and understand the series. Have a question below:

> UEFI Specification version 2.9 introduces the concept of memory
> acceptance. Some Virtual Machine platforms, such as Intel TDX or AMD
> SEV-SNP, require memory to be accepted before it can be used by the
> guest. Accepting happens via a protocol specific to the Virtual Machine
> platform.
> 
> There are several ways kernel can deal with unaccepted memory:
> 
>   1. Accept all the memory during the boot. It is easy to implement and
>      it doesn't have runtime cost once the system is booted. The downside
>      is very long boot time.
> 
>      Accept can be parallelized to multiple CPUs to keep it manageable
>      (i.e. via DEFERRED_STRUCT_PAGE_INIT), but it tends to saturate
>      memory bandwidth and does not scale beyond the point.
> 
>   2. Accept a block of memory on the first use. It requires more
>      infrastructure and changes in page allocator to make it work, but
>      it provides good boot time.
> 
>      On-demand memory accept means latency spikes every time kernel steps
>      onto a new memory block. The spikes will go away once workload data
>      set size gets stabilized or all memory gets accepted.
> 
>   3. Accept all memory in background. Introduce a thread (or multiple)
>      that gets memory accepted proactively. It will minimize time the
>      system experience latency spikes on memory allocation while keeping
>      low boot time.
> 
>      This approach cannot function on its own. It is an extension of #2:
>      background memory acceptance requires functional scheduler, but the
>      page allocator may need to tap into unaccepted memory before that.
> 
>      The downside of the approach is that these threads also steal CPU
>      cycles and memory bandwidth from the user's workload and may hurt
>      user experience.
> 
> Implement #2 for now. It is a reasonable default. Some workloads may
> want to use #1 or #3 and they can be implemented later based on user's
> demands.
> 
> Support of unaccepted memory requires a few changes in core-mm code:
> 
>    - memblock has to accept memory on allocation;
> 
>    - page allocator has to accept memory on the first allocation of the
>      page;
> 
> Memblock change is trivial.
> 
> The page allocator is modified to accept pages on the first allocation.
> The new page type (encoded in the _mapcount) -- PageUnaccepted() -- is
> used to indicate that the page requires acceptance.
> 
> Architecture has to provide two helpers if it wants to support
> unaccepted memory:
> 
>   - accept_memory() makes a range of physical addresses accepted.
> 
>   - memory_is_unaccepted() checks anything within the range of physical
>     addresses requires acceptance.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Acked-by: Mike Rapoport <rppt@linux.ibm.com>	# memblock
> ---
>   include/linux/page-flags.h | 31 ++++++++++++++
>   mm/internal.h              | 12 ++++++
>   mm/memblock.c              |  9 ++++
>   mm/page_alloc.c            | 87 +++++++++++++++++++++++++++++++++++++-
>   4 files changed, 137 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 9d8eeaa67d05..7f21267366a9 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -928,6 +928,14 @@ static inline bool is_page_hwpoison(struct page *page)
>   #define PG_offline	0x00000100
>   #define PG_table	0x00000200
>   #define PG_guard	0x00000400
> +#define PG_unaccepted	0x00000800
> +
> +/*
> + * Page types allowed at page_expected_state()
> + *
> + * PageUnaccepted() will get cleared in post_alloc_hook().
> + */
> +#define PAGE_TYPES_EXPECTED	PG_unaccepted
>   
>   #define PageType(page, flag)						\
>   	((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
> @@ -953,6 +961,18 @@ static __always_inline void __ClearPage##uname(struct page *page)	\
>   	page->page_type |= PG_##lname;					\
>   }
>   
> +#define PAGE_TYPE_OPS_FALSE(uname)					\
> +static __always_inline int Page##uname(struct page *page)		\
> +{									\
> +	return false;							\
> +}									\
> +static __always_inline void __SetPage##uname(struct page *page)		\
> +{									\
> +}									\
> +static __always_inline void __ClearPage##uname(struct page *page)	\
> +{									\
> +}
> +
>   /*
>    * PageBuddy() indicates that the page is free and in the buddy system
>    * (see mm/page_alloc.c).
> @@ -983,6 +1003,17 @@ PAGE_TYPE_OPS(Buddy, buddy)
>    */
>   PAGE_TYPE_OPS(Offline, offline)
>   
> +/*
> + * PageUnaccepted() indicates that the page has to be "accepted" before it can
> + * be read or written. The page allocator must call accept_page() before
> + * touching the page or returning it to the caller.
> + */
> +#ifdef CONFIG_UNACCEPTED_MEMORY
> +PAGE_TYPE_OPS(Unaccepted, unaccepted)
> +#else
> +PAGE_TYPE_OPS_FALSE(Unaccepted)
> +#endif
> +
>   extern void page_offline_freeze(void);
>   extern void page_offline_thaw(void);
>   extern void page_offline_begin(void);
> diff --git a/mm/internal.h b/mm/internal.h
> index cf16280ce132..3fd5d8f90492 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -758,4 +758,16 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
>   
>   DECLARE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
>   
> +#ifndef CONFIG_UNACCEPTED_MEMORY
> +static inline bool range_contains_unaccepted_memory(phys_addr_t start,
> +						    phys_addr_t end)
> +{
> +	return false;
> +}
> +
> +static inline void accept_memory(phys_addr_t start, phys_addr_t end)
> +{
> +}
> +#endif
> +
>   #endif	/* __MM_INTERNAL_H */
> diff --git a/mm/memblock.c b/mm/memblock.c
> index e4f03a6e8e56..a1f7f8b304d5 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1405,6 +1405,15 @@ phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
>   		 */
>   		kmemleak_alloc_phys(found, size, 0, 0);
>   
> +	/*
> +	 * Some Virtual Machine platforms, such as Intel TDX or AMD SEV-SNP,
> +	 * require memory to be accepted before it can be used by the
> +	 * guest.
> +	 *
> +	 * Accept the memory of the allocated buffer.
> +	 */
> +	accept_memory(found, found + size);

If both Intel TDX and AMD SEV-SNP requires the memory to be accepted 
before it can be used by the guest. In what other use cases (apart from 
memory hotplug), the lazy memory acceptance will be useful?

Thank you!
Pankaj

> +
>   	return found;
>   }
>   
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 0e42038382c1..c8b6e29f4402 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -121,6 +121,12 @@ typedef int __bitwise fpi_t;
>    */
>   #define FPI_SKIP_KASAN_POISON	((__force fpi_t)BIT(2))
>   
> +/*
> + * Check if the page needs to be marked as PageUnaccepted().
> + * Used for the new pages added to the buddy allocator for the first time.
> + */
> +#define FPI_UNACCEPTED_SLOWPATH	((__force fpi_t)BIT(3))
> +
>   /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
>   static DEFINE_MUTEX(pcp_batch_high_lock);
>   #define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
> @@ -1023,6 +1029,32 @@ buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
>   	return page_is_buddy(higher_page, higher_buddy, order + 1);
>   }
>   
> +/*
> + * Page acceptance can be very slow. Do not call under critical locks.
> + */
> +static void accept_page(struct page *page, unsigned int order)
> +{
> +	phys_addr_t start = page_to_phys(page);
> +	int i;
> +
> +	accept_memory(start, start + (PAGE_SIZE << order));
> +	__ClearPageUnaccepted(page);
> +
> +	/* Assert that there is no PageUnaccepted() on tail pages */
> +	if (IS_ENABLED(CONFIG_DEBUG_VM)) {
> +		for (i = 1; i < (1 << order); i++)
> +			VM_BUG_ON_PAGE(PageUnaccepted(page + i), page + i);
> +	}
> +}
> +
> +static bool page_is_unaccepted(struct page *page, unsigned int order)
> +{
> +	phys_addr_t start = page_to_phys(page);
> +	phys_addr_t end = start + (PAGE_SIZE << order);
> +
> +	return range_contains_unaccepted_memory(start, end);
> +}
> +
>   /*
>    * Freeing function for a buddy system allocator.
>    *
> @@ -1058,6 +1090,7 @@ static inline void __free_one_page(struct page *page,
>   	unsigned long combined_pfn;
>   	struct page *buddy;
>   	bool to_tail;
> +	bool page_needs_acceptance = false;
>   
>   	VM_BUG_ON(!zone_is_initialized(zone));
>   	VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);
> @@ -1069,6 +1102,11 @@ static inline void __free_one_page(struct page *page,
>   	VM_BUG_ON_PAGE(pfn & ((1 << order) - 1), page);
>   	VM_BUG_ON_PAGE(bad_range(zone, page), page);
>   
> +	if (PageUnaccepted(page)) {
> +		page_needs_acceptance = true;
> +		__ClearPageUnaccepted(page);
> +	}
> +
>   continue_merging:
>   	while (order < max_order) {
>   		if (compaction_capture(capc, page, order, migratetype)) {
> @@ -1089,6 +1127,13 @@ static inline void __free_one_page(struct page *page,
>   			clear_page_guard(zone, buddy, order, migratetype);
>   		else
>   			del_page_from_free_list(buddy, zone, order);
> +
> +		/* Mark page unaccepted if any of merged pages were unaccepted */
> +		if (PageUnaccepted(buddy)) {
> +			page_needs_acceptance = true;
> +			__ClearPageUnaccepted(buddy);
> +		}
> +
>   		combined_pfn = buddy_pfn & pfn;
>   		page = page + (combined_pfn - pfn);
>   		pfn = combined_pfn;
> @@ -1124,6 +1169,23 @@ static inline void __free_one_page(struct page *page,
>   done_merging:
>   	set_buddy_order(page, order);
>   
> +	/*
> +	 * The page gets marked as PageUnaccepted() if any of merged-in pages
> +	 * is PageUnaccepted().
> +	 *
> +	 * New pages, just being added to buddy allocator, do not have
> +	 * PageUnaccepted() set. FPI_UNACCEPTED_SLOWPATH indicates that the
> +	 * page is new and page_is_unaccepted() check is required to
> +	 * determinate if acceptance is required.
> +	 *
> +	 * Avoid calling page_is_unaccepted() if it is known that the page
> +	 * needs acceptance. It can be costly.
> +	 */
> +	if (!page_needs_acceptance && (fpi_flags & FPI_UNACCEPTED_SLOWPATH))
> +		page_needs_acceptance = page_is_unaccepted(page, order);
> +	if (page_needs_acceptance)
> +		__SetPageUnaccepted(page);
> +
>   	if (fpi_flags & FPI_TO_TAIL)
>   		to_tail = true;
>   	else if (is_shuffle_order(order))
> @@ -1149,7 +1211,13 @@ static inline void __free_one_page(struct page *page,
>   static inline bool page_expected_state(struct page *page,
>   					unsigned long check_flags)
>   {
> -	if (unlikely(atomic_read(&page->_mapcount) != -1))
> +	/*
> +	 * The page must not be mapped to userspace and must not have
> +	 * a PageType other than listed in PAGE_TYPES_EXPECTED.
> +	 *
> +	 * Note, bit cleared means the page type is set.
> +	 */
> +	if (unlikely((atomic_read(&page->_mapcount) | PAGE_TYPES_EXPECTED) != -1))
>   		return false;
>   
>   	if (unlikely((unsigned long)page->mapping |
> @@ -1654,7 +1722,9 @@ void __free_pages_core(struct page *page, unsigned int order)
>   	 * Bypass PCP and place fresh pages right to the tail, primarily
>   	 * relevant for memory onlining.
>   	 */
> -	__free_pages_ok(page, order, FPI_TO_TAIL | FPI_SKIP_KASAN_POISON);
> +	__free_pages_ok(page, order,
> +			FPI_TO_TAIL | FPI_SKIP_KASAN_POISON |
> +			FPI_UNACCEPTED_SLOWPATH);
>   }
>   
>   #ifdef CONFIG_NUMA
> @@ -1807,6 +1877,9 @@ static void __init deferred_free_range(unsigned long pfn,
>   		return;
>   	}
>   
> +	/* Accept chunks smaller than page-block upfront */
> +	accept_memory(pfn << PAGE_SHIFT, (pfn + nr_pages) << PAGE_SHIFT);
> +
>   	for (i = 0; i < nr_pages; i++, page++, pfn++) {
>   		if ((pfn & (pageblock_nr_pages - 1)) == 0)
>   			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
> @@ -2266,6 +2339,13 @@ static inline void expand(struct zone *zone, struct page *page,
>   		if (set_page_guard(zone, &page[size], high, migratetype))
>   			continue;
>   
> +		/*
> +		 * Transfer PageUnaccepted() to the newly split pages so
> +		 * they can be accepted after dropping the zone lock.
> +		 */
> +		if (PageUnaccepted(page))
> +			__SetPageUnaccepted(&page[size]);
> +
>   		add_to_free_list(&page[size], zone, high, migratetype);
>   		set_buddy_order(&page[size], high);
>   	}
> @@ -2396,6 +2476,9 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
>   	 */
>   	kernel_unpoison_pages(page, 1 << order);
>   
> +	if (PageUnaccepted(page))
> +		accept_page(page, order);
> +
>   	/*
>   	 * As memory initialization might be integrated into KASAN,
>   	 * KASAN unpoisoning and memory initializion code must be

Re: [PATCHv6 02/15] mm: Add support for unaccepted memory

[Kirill A. Shutemov]

On Thu, May 19, 2022 at 12:43:15PM +0200, Gupta, Pankaj wrote:
> If both Intel TDX and AMD SEV-SNP requires the memory to be accepted before
> it can be used by the guest. In what other use cases (apart from memory
> hotplug), the lazy memory acceptance will be useful?

It is nothing to do with hotplug.

Any memory has to be accepted before it can be used inside the TDX or
SEV-SNP guest. It can happen upfront, before kernel gets control (like by
firmware) or by kernel. The idea is to accept small portion of the memory
upfront and leave the rest to the kernel. The reason why delaying
acceptance make sense is boot time. We want the guest to start doing
useful stuff as fast as possible.

-- 
 Kirill A. Shutemov

Re: [PATCHv6 02/15] mm: Add support for unaccepted memory

[Gupta, Pankaj]

> On Thu, May 19, 2022 at 12:43:15PM +0200, Gupta, Pankaj wrote:
>> If both Intel TDX and AMD SEV-SNP requires the memory to be accepted before
>> it can be used by the guest. In what other use cases (apart from memory
>> hotplug), the lazy memory acceptance will be useful?
> 
> It is nothing to do with hotplug.
> 
> Any memory has to be accepted before it can be used inside the TDX or
> SEV-SNP guest. It can happen upfront, before kernel gets control (like by
> firmware) or by kernel. The idea is to accept small portion of the memory
> upfront and leave the rest to the kernel. The reason why delaying
> acceptance make sense is boot time. We want the guest to start doing
> useful stuff as fast as possible.

o.k. That answers my question. Thank you!

Best regards,
Pankaj

Re: [PATCHv6 02/15] mm: Add support for unaccepted memory

[David Hildenbrand]

On 17.05.22 17:34, Kirill A. Shutemov wrote:
> UEFI Specification version 2.9 introduces the concept of memory
> acceptance. Some Virtual Machine platforms, such as Intel TDX or AMD
> SEV-SNP, require memory to be accepted before it can be used by the
> guest. Accepting happens via a protocol specific to the Virtual Machine
> platform.
> 
> There are several ways kernel can deal with unaccepted memory:
> 
>  1. Accept all the memory during the boot. It is easy to implement and
>     it doesn't have runtime cost once the system is booted. The downside
>     is very long boot time.
> 
>     Accept can be parallelized to multiple CPUs to keep it manageable
>     (i.e. via DEFERRED_STRUCT_PAGE_INIT), but it tends to saturate
>     memory bandwidth and does not scale beyond the point.
> 
>  2. Accept a block of memory on the first use. It requires more
>     infrastructure and changes in page allocator to make it work, but
>     it provides good boot time.
> 
>     On-demand memory accept means latency spikes every time kernel steps
>     onto a new memory block. The spikes will go away once workload data
>     set size gets stabilized or all memory gets accepted.
> 
>  3. Accept all memory in background. Introduce a thread (or multiple)
>     that gets memory accepted proactively. It will minimize time the
>     system experience latency spikes on memory allocation while keeping
>     low boot time.
> 
>     This approach cannot function on its own. It is an extension of #2:
>     background memory acceptance requires functional scheduler, but the
>     page allocator may need to tap into unaccepted memory before that.
> 
>     The downside of the approach is that these threads also steal CPU
>     cycles and memory bandwidth from the user's workload and may hurt
>     user experience.
> 
> Implement #2 for now. It is a reasonable default. Some workloads may
> want to use #1 or #3 and they can be implemented later based on user's
> demands.
> 
> Support of unaccepted memory requires a few changes in core-mm code:
> 
>   - memblock has to accept memory on allocation;
> 
>   - page allocator has to accept memory on the first allocation of the
>     page;
> 
> Memblock change is trivial.
> 
> The page allocator is modified to accept pages on the first allocation.
> The new page type (encoded in the _mapcount) -- PageUnaccepted() -- is
> used to indicate that the page requires acceptance.
> 
> Architecture has to provide two helpers if it wants to support
> unaccepted memory:
> 
>  - accept_memory() makes a range of physical addresses accepted.
> 
>  - memory_is_unaccepted() checks anything within the range of physical
>    addresses requires acceptance.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Acked-by: Mike Rapoport <rppt@linux.ibm.com>	# memblock


[...]

> +/*
> + * Page acceptance can be very slow. Do not call under critical locks.
> + */
> +static void accept_page(struct page *page, unsigned int order)
> +{
> +	phys_addr_t start = page_to_phys(page);
> +	int i;
> +
> +	accept_memory(start, start + (PAGE_SIZE << order));
> +	__ClearPageUnaccepted(page);
> +
> +	/* Assert that there is no PageUnaccepted() on tail pages */
> +	if (IS_ENABLED(CONFIG_DEBUG_VM)) {
> +		for (i = 1; i < (1 << order); i++)
> +			VM_BUG_ON_PAGE(PageUnaccepted(page + i), page + i);
> +	}
> +}
> +
> +static bool page_is_unaccepted(struct page *page, unsigned int order)

Nit: I'd call this page_contains_unaccepted(), otherwise it sounds like
we're just testing the flag.

> +{
> +	phys_addr_t start = page_to_phys(page);
> +	phys_addr_t end = start + (PAGE_SIZE << order);
> +
> +	return range_contains_unaccepted_memory(start, end);
> +}
> +


[...]

>  
>  #ifdef CONFIG_NUMA
> @@ -1807,6 +1877,9 @@ static void __init deferred_free_range(unsigned long pfn,
>  		return;
>  	}
>  
> +	/* Accept chunks smaller than page-block upfront */
> +	accept_memory(pfn << PAGE_SHIFT, (pfn + nr_pages) << PAGE_SHIFT);

PFN_PHYS()

> +
>  	for (i = 0; i < nr_pages; i++, page++, pfn++) {
>  		if ((pfn & (pageblock_nr_pages - 1)) == 0)
>  			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
> @@ -2266,6 +2339,13 @@ static inline void expand(struct zone *zone, struct page *page,
>  		if (set_page_guard(zone, &page[size], high, migratetype))
>  			continue;
>  
> +		/*
> +		 * Transfer PageUnaccepted() to the newly split pages so
> +		 * they can be accepted after dropping the zone lock.
> +		 */
> +		if (PageUnaccepted(page))
> +			__SetPageUnaccepted(&page[size]);
> +
>  		add_to_free_list(&page[size], zone, high, migratetype);
>  		set_buddy_order(&page[size], high);
>  	}
> @@ -2396,6 +2476,9 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
>  	 */
>  	kernel_unpoison_pages(page, 1 << order);
>  
> +	if (PageUnaccepted(page))
> +		accept_page(page, order);

Nit: Just move the PageUnaccepted() call into accept_page(), so all type
testing and clearing code is in a single location.

> +
>  	/*
>  	 * As memory initialization might be integrated into KASAN,
>  	 * KASAN unpoisoning and memory initializion code must be


Apart from that, LGTM. If the temporary clearing of the unaccepted type
is ever an issue (e.g., when we want to exclude reading them in
/proc/kcore), we can think of ways to avoid that race.

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb

Re: [PATCHv6 03/15] efi/x86: Get full memory map in allocate_e820()

[David Hildenbrand]

On 17.05.22 17:34, Kirill A. Shutemov wrote:
> Currently allocate_e820() only interested in the size of map and size of
> memory descriptor to determine how many e820 entries the kernel needs.
> 
> UEFI Specification version 2.9 introduces a new memory type --
> unaccepted memory. To track unaccepted memory kernel needs to allocate
> a bitmap. The size of the bitmap is dependent on the maximum physical
> address present in the system. A full memory map is required to find
> the maximum address.
> 
> Modify allocate_e820() to get a full memory map.

Usually we use max_pfn, if we want to know the maximum pfn that's
present in the system (well, IIRC, excluding hotunplug).

How exactly will this (different?) maximum from UEFI for the bitmap
interact with

max_pfn = e820__end_of_ram_pfn();

from e820 in existing code

?

-- 
Thanks,

David / dhildenb

Re: [PATCHv6 15/15] mm/vmstat: Add counter for memory accepting

[David Hildenbrand]

On 17.05.22 17:34, Kirill A. Shutemov wrote:
> The counter increased every time kernel accepts a memory region.
> 
> The counter allows to see if memory acceptation is still ongoing and
> contributes to memory allocation latency.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
>  arch/x86/mm/unaccepted_memory.c | 1 +
>  include/linux/vm_event_item.h   | 3 +++
>  mm/vmstat.c                     | 3 +++
>  3 files changed, 7 insertions(+)
> 
> diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
> index 6ecd79101922..fe1dabfae326 100644
> --- a/arch/x86/mm/unaccepted_memory.c
> +++ b/arch/x86/mm/unaccepted_memory.c
> @@ -74,6 +74,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
>  		}
>  
>  		bitmap_clear(bitmap, range_start, len);
> +		count_vm_events(ACCEPT_MEMORY, len * PMD_SIZE / PAGE_SIZE);
>  

It's a bit weird that this is accounted from arch code. Also, I'm a bit
confused about the granularity here (PMD_SIZE).

>  		/* In early boot nr_unaccepted is not yet initialized */
>  		if (nr_unaccepted) {
> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> index 16a0a4fd000b..6a468164a2f9 100644
> --- a/include/linux/vm_event_item.h
> +++ b/include/linux/vm_event_item.h
> @@ -136,6 +136,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>  #ifdef CONFIG_X86
>  		DIRECT_MAP_LEVEL2_SPLIT,
>  		DIRECT_MAP_LEVEL3_SPLIT,
> +#endif
> +#ifdef CONFIG_UNACCEPTED_MEMORY
> +		ACCEPT_MEMORY,
>  #endif
>  		NR_VM_EVENT_ITEMS
>  };
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index b75b1a64b54c..4c9197f32406 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1397,6 +1397,9 @@ const char * const vmstat_text[] = {
>  	"direct_map_level2_splits",
>  	"direct_map_level3_splits",
>  #endif
> +#ifdef CONFIG_UNACCEPTED_MEMORY
> +	"accept_memory",
> +#endif
>  #endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
>  };
>  #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA || CONFIG_MEMCG */

How exactly would I be able to figure out if "memory acceptation is
still ongoing" if there is one last remaining page stuck at the tail of
the freelist?

Wouldn't it make more sense to actually count the number of unaccepted
pages in the buddy? Once that number drops to 0, one knows that there is
no unaccepted memory left in the buddy.

-- 
Thanks,

David / dhildenb

Re: [PATCHv6 03/15] efi/x86: Get full memory map in allocate_e820()

[Kirill A. Shutemov]

On Wed, Jun 01, 2022 at 11:00:23AM +0200, David Hildenbrand wrote:
> On 17.05.22 17:34, Kirill A. Shutemov wrote:
> > Currently allocate_e820() only interested in the size of map and size of
> > memory descriptor to determine how many e820 entries the kernel needs.
> > 
> > UEFI Specification version 2.9 introduces a new memory type --
> > unaccepted memory. To track unaccepted memory kernel needs to allocate
> > a bitmap. The size of the bitmap is dependent on the maximum physical
> > address present in the system. A full memory map is required to find
> > the maximum address.
> > 
> > Modify allocate_e820() to get a full memory map.
> 
> Usually we use max_pfn, if we want to know the maximum pfn that's
> present in the system (well, IIRC, excluding hotunplug).
> 
> How exactly will this (different?) maximum from UEFI for the bitmap
> interact with
> 
> max_pfn = e820__end_of_ram_pfn();
> 
> from e820 in existing code
> 
> ?

I'm not sure I understand the question.

On EFI system, E820 is constructed based on EFI memory map and size of
bitmap calculated based of EFI memmap will always be enough to address all
memory. e820__end_of_ram_pfn() can be smaller than what what we calculate
as size of memory here, if kernel reserve very top of the memory, but it
will never be larger.

Later during the boot we use e820__end_of_ram_pfn() to infer size of
bitmap and it is safe.

-- 
 Kirill A. Shutemov

Re: [PATCHv6 03/15] efi/x86: Get full memory map in allocate_e820()

[David Hildenbrand]

On 01.06.22 16:35, Kirill A. Shutemov wrote:
> On Wed, Jun 01, 2022 at 11:00:23AM +0200, David Hildenbrand wrote:
>> On 17.05.22 17:34, Kirill A. Shutemov wrote:
>>> Currently allocate_e820() only interested in the size of map and size of
>>> memory descriptor to determine how many e820 entries the kernel needs.
>>>
>>> UEFI Specification version 2.9 introduces a new memory type --
>>> unaccepted memory. To track unaccepted memory kernel needs to allocate
>>> a bitmap. The size of the bitmap is dependent on the maximum physical
>>> address present in the system. A full memory map is required to find
>>> the maximum address.
>>>
>>> Modify allocate_e820() to get a full memory map.
>>
>> Usually we use max_pfn, if we want to know the maximum pfn that's
>> present in the system (well, IIRC, excluding hotunplug).
>>
>> How exactly will this (different?) maximum from UEFI for the bitmap
>> interact with
>>
>> max_pfn = e820__end_of_ram_pfn();
>>
>> from e820 in existing code
>>
>> ?
> 
> I'm not sure I understand the question.

Essentially, if the PFN you calculate here for the bitmap size will
essentially match later max_pfn.

> 
> On EFI system, E820 is constructed based on EFI memory map and size of
> bitmap calculated based of EFI memmap will always be enough to address all
> memory. e820__end_of_ram_pfn() can be smaller than what what we calculate
> as size of memory here, if kernel reserve very top of the memory, but it
> will never be larger.
> 
> Later during the boot we use e820__end_of_ram_pfn() to infer size of
> bitmap and it is safe.
> 


-- 
Thanks,

David / dhildenb

Re: [PATCHv6 15/15] mm/vmstat: Add counter for memory accepting

[Kirill A. Shutemov]

On Wed, Jun 01, 2022 at 11:05:40AM +0200, David Hildenbrand wrote:
> On 17.05.22 17:34, Kirill A. Shutemov wrote:
> > The counter increased every time kernel accepts a memory region.
> > 
> > The counter allows to see if memory acceptation is still ongoing and
> > contributes to memory allocation latency.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > ---
> >  arch/x86/mm/unaccepted_memory.c | 1 +
> >  include/linux/vm_event_item.h   | 3 +++
> >  mm/vmstat.c                     | 3 +++
> >  3 files changed, 7 insertions(+)
> > 
> > diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
> > index 6ecd79101922..fe1dabfae326 100644
> > --- a/arch/x86/mm/unaccepted_memory.c
> > +++ b/arch/x86/mm/unaccepted_memory.c
> > @@ -74,6 +74,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
> >  		}
> >  
> >  		bitmap_clear(bitmap, range_start, len);
> > +		count_vm_events(ACCEPT_MEMORY, len * PMD_SIZE / PAGE_SIZE);
> >  
> 
> It's a bit weird that this is accounted from arch code

That's very serialization happens.

We can do it in the core mm if we can tolerate sporious vmcount bump.
Otherwise it has to happen under the lock in the arch code.

> Also, I'm a bit
> confused about the granularity here (PMD_SIZE).

That's how we track it in x86. The count itself is in pages. Different
arch can choose different granularity.

> >  		/* In early boot nr_unaccepted is not yet initialized */
> >  		if (nr_unaccepted) {
> > diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> > index 16a0a4fd000b..6a468164a2f9 100644
> > --- a/include/linux/vm_event_item.h
> > +++ b/include/linux/vm_event_item.h
> > @@ -136,6 +136,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
> >  #ifdef CONFIG_X86
> >  		DIRECT_MAP_LEVEL2_SPLIT,
> >  		DIRECT_MAP_LEVEL3_SPLIT,
> > +#endif
> > +#ifdef CONFIG_UNACCEPTED_MEMORY
> > +		ACCEPT_MEMORY,
> >  #endif
> >  		NR_VM_EVENT_ITEMS
> >  };
> > diff --git a/mm/vmstat.c b/mm/vmstat.c
> > index b75b1a64b54c..4c9197f32406 100644
> > --- a/mm/vmstat.c
> > +++ b/mm/vmstat.c
> > @@ -1397,6 +1397,9 @@ const char * const vmstat_text[] = {
> >  	"direct_map_level2_splits",
> >  	"direct_map_level3_splits",
> >  #endif
> > +#ifdef CONFIG_UNACCEPTED_MEMORY
> > +	"accept_memory",
> > +#endif
> >  #endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
> >  };
> >  #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA || CONFIG_MEMCG */
> 
> How exactly would I be able to figure out if "memory acceptation is
> still ongoing" if there is one last remaining page stuck at the tail of
> the freelist?

"still ongoing" in sense it is happening now, like if it increases system
does memory accept.

> Wouldn't it make more sense to actually count the number of unaccepted
> pages in the buddy? Once that number drops to 0, one knows that there is
> no unaccepted memory left in the buddy.

Patch 10/15 does this, but not in buddy.

-- 
 Kirill A. Shutemov

Re: [PATCHv6 03/15] efi/x86: Get full memory map in allocate_e820()

[Kirill A. Shutemov]

On Wed, Jun 01, 2022 at 04:39:16PM +0200, David Hildenbrand wrote:
> On 01.06.22 16:35, Kirill A. Shutemov wrote:
> > On Wed, Jun 01, 2022 at 11:00:23AM +0200, David Hildenbrand wrote:
> >> On 17.05.22 17:34, Kirill A. Shutemov wrote:
> >>> Currently allocate_e820() only interested in the size of map and size of
> >>> memory descriptor to determine how many e820 entries the kernel needs.
> >>>
> >>> UEFI Specification version 2.9 introduces a new memory type --
> >>> unaccepted memory. To track unaccepted memory kernel needs to allocate
> >>> a bitmap. The size of the bitmap is dependent on the maximum physical
> >>> address present in the system. A full memory map is required to find
> >>> the maximum address.
> >>>
> >>> Modify allocate_e820() to get a full memory map.
> >>
> >> Usually we use max_pfn, if we want to know the maximum pfn that's
> >> present in the system (well, IIRC, excluding hotunplug).
> >>
> >> How exactly will this (different?) maximum from UEFI for the bitmap
> >> interact with
> >>
> >> max_pfn = e820__end_of_ram_pfn();
> >>
> >> from e820 in existing code
> >>
> >> ?
> > 
> > I'm not sure I understand the question.
> 
> Essentially, if the PFN you calculate here for the bitmap size will
> essentially match later max_pfn.

Yes, generally. But is can decrease if kernel transit memory from TYPE_RAM
to TYPE_RESERVE. In any case we will not step out of the allocated bitmap.

-- 
 Kirill A. Shutemov

Re: [PATCHv6 10/15] x86/mm: Report unaccepted memory in /proc/meminfo

[David Hildenbrand]

On 17.05.22 17:34, Kirill A. Shutemov wrote:
> Track amount of unaccepted memory and report it in /proc/meminfo.

I feel like instead of doing this arch specific tracking here, we should
simply report the total number of unaccepted (base) pages in the buddy.

When the system boots up, the number will rise as unaccepted memory gets
exposed to the buddy. But especially once user space is up and running,
that number should only go down.

Once it hits zero, there is no unaccepted memory left in the buddy and
there won't be any performance surprises anymote -- and AFAIKT, that's
what we really care about.

-- 
Thanks,

David / dhildenb