[PATCHv9 00/14] mm, x86/cc: Implement support for unaccepted memory

[PATCHv9 00/14] 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.

-- Fragmentation study --

Vlastimil and Mel were concern about effect of unaccepted memory on
fragmentation prevention measures in page allocator. I tried to evaluate
it, but it is tricky. As suggested I tried to run multiple parallel kernel
builds and follow how often kmem:mm_page_alloc_extfrag gets hit.

I don't like the results. Not because unaccepted memory is slow, but
because the test is way too noisy to produce sensible information.

So, I run 8 parallel builds of kernel, 16 jobs each in a VM with 16 CPU
and 16G of RAM. I compared unpatched base-line (mm-unstable) with the tree
that has patchset applied. For the later case, all memory above 1G was
considered unaccepted with fake_unaccepted_start=1G. Around 14G of RAM was
accounted as unaccepted after the boot. The test got all memory accepted.

		kmem:mm_page_alloc_extfrag		Time elapsed
Base line:
Run 1		837					1803.21s
Run 2		3,845					1785.87s
Run 3		1,704					1883.59s

Patched:
Run 1		905					1876.02s
Run 2		845					1758.50s
Run 3		1276					1876.13s

As you can see the numbers are all over the place.

The good news is that unaccepted memory doesn't make picture notably worse.

I am open to suggestions on how to test it better.

Also, feel free to play with it yourself. fake_unaccepted_start= doesn't
require any special setup.

--

The tree can be found here:

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

The patchset depends on MAX_ORDER changes in MM tree.

v9:
 - Accept memory up to high watermark when kernel runs out of free memory;
 - Treat unaccepted memory as unusable in __zone_watermark_unusable_free();
 - Per-zone unaccepted memory accounting;
 - All pages on unaccepted list are MAX_ORDER now;
 - accept_memory=eager in cmdline to pre-accept memory during the boot;
 - Implement fake unaccepted memory;
 - Sysfs handle to accept memory manually;
 - Drop PageUnaccepted();
 - Rename unaccepted_pages static key to zones_with_unaccepted_pages;
v8:
 - Rewrite core-mm support for unaccepted memory (patch 02/14);
 - s/UnacceptedPages/Unaccepted/ in meminfo;
 - Drop arch/x86/boot/compressed/compiler.h;
 - Fix build errors;
 - Adjust commit messages and comments;
 - Reviewed-bys from Dave and Borislav;
 - Rebased to tip/master.
v7:
 - Rework meminfo counter to use PageUnaccepted() and move to generic code;
 - Fix range_contains_unaccepted_memory() on machines without unaccepted memory;
 - Add Reviewed-by from David;
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 (14):
  x86/boot: Centralize __pa()/__va() definitions
  mm: Add support for unaccepted memory
  mm/page_alloc: Fake unaccepted memory
  mm/page_alloc: Add sysfs handle to accept accept_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/tdx: Make _tdx_hypercall() and __tdx_module_call() available in
    boot stub
  x86/tdx: Refactor try_accept_one()
  x86/tdx: Add unaccepted memory support

 Documentation/x86/zero-page.rst          |   1 +
 arch/x86/Kconfig                         |   2 +
 arch/x86/boot/bitops.h                   |  40 ++++
 arch/x86/boot/compressed/Makefile        |   3 +-
 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/efi.h           |   1 +
 arch/x86/boot/compressed/error.c         |  19 ++
 arch/x86/boot/compressed/error.h         |   1 +
 arch/x86/boot/compressed/find.c          |  54 +++++
 arch/x86/boot/compressed/find.h          |  79 ++++++++
 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           | 122 +++++++++++
 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-shared.c    |   2 +
 arch/x86/boot/compressed/tdx.c           |  39 ++++
 arch/x86/coco/tdx/Makefile               |   2 +-
 arch/x86/coco/tdx/tdx-shared.c           |  95 +++++++++
 arch/x86/coco/tdx/tdx.c                  | 118 +----------
 arch/x86/include/asm/page.h              |   3 +
 arch/x86/include/asm/shared/tdx.h        |  53 +++++
 arch/x86/include/asm/tdx.h               |  21 +-
 arch/x86/include/asm/unaccepted_memory.h |  16 ++
 arch/x86/include/uapi/asm/bootparam.h    |   2 +-
 arch/x86/kernel/e820.c                   |  17 ++
 arch/x86/mm/Makefile                     |   2 +
 arch/x86/mm/unaccepted_memory.c          | 107 ++++++++++
 drivers/base/node.c                      |   7 +
 drivers/firmware/efi/Kconfig             |  14 ++
 drivers/firmware/efi/efi.c               |   1 +
 drivers/firmware/efi/libstub/x86-stub.c  |  98 +++++++--
 fs/proc/meminfo.c                        |   5 +
 include/linux/efi.h                      |   3 +-
 include/linux/mmzone.h                   |   8 +
 mm/internal.h                            |  13 ++
 mm/memblock.c                            |   9 +
 mm/mm_init.c                             |   7 +
 mm/page_alloc.c                          | 246 +++++++++++++++++++++++
 mm/vmstat.c                              |   3 +
 47 files changed, 1368 insertions(+), 176 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/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/boot/compressed/tdx-shared.c
 create mode 100644 arch/x86/coco/tdx/tdx-shared.c
 create mode 100644 arch/x86/include/asm/unaccepted_memory.h
 create mode 100644 arch/x86/mm/unaccepted_memory.c

-- 
2.39.2

[PATCHv9 01/14] 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>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.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 321a5011042d..bcc956c17872 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 20118fb7c53b..2f155a0e3041 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 d63ad8f99f83..014b89c89088 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
 
-- 
2.39.2

[PATCHv9 02/14] 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.

The patch implements #1 and #2 for now. #2 is the default. Some
workloads may want to use #1 with accept_memory=eager in kernel
command line. #3 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. New memory gets accepted
before putting pages on free lists. It is done lazily: only accept new
pages when we run out of already accepted memory. The memory gets
accepted until the high watermark is reached.

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

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

 - range_contains_unaccepted_memory() 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
---
 drivers/base/node.c    |   7 ++
 fs/proc/meminfo.c      |   5 ++
 include/linux/mmzone.h |   8 ++
 mm/internal.h          |  13 ++++
 mm/memblock.c          |   9 +++
 mm/mm_init.c           |   7 ++
 mm/page_alloc.c        | 161 +++++++++++++++++++++++++++++++++++++++++
 mm/vmstat.c            |   3 +
 8 files changed, 213 insertions(+)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index b46db17124f3..655975946ef6 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -448,6 +448,9 @@ static ssize_t node_read_meminfo(struct device *dev,
 			     "Node %d ShmemPmdMapped: %8lu kB\n"
 			     "Node %d FileHugePages: %8lu kB\n"
 			     "Node %d FilePmdMapped: %8lu kB\n"
+#endif
+#ifdef CONFIG_UNACCEPTED_MEMORY
+			     "Node %d Unaccepted:     %8lu kB\n"
 #endif
 			     ,
 			     nid, K(node_page_state(pgdat, NR_FILE_DIRTY)),
@@ -477,6 +480,10 @@ static ssize_t node_read_meminfo(struct device *dev,
 			     nid, K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED)),
 			     nid, K(node_page_state(pgdat, NR_FILE_THPS)),
 			     nid, K(node_page_state(pgdat, NR_FILE_PMDMAPPED))
+#endif
+#ifdef CONFIG_UNACCEPTED_MEMORY
+			     ,
+			     nid, K(sum_zone_node_page_state(nid, NR_UNACCEPTED))
 #endif
 			    );
 	len += hugetlb_report_node_meminfo(buf, len, nid);
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index b43d0bd42762..8dca4d6d96c7 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -168,6 +168,11 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 		    global_zone_page_state(NR_FREE_CMA_PAGES));
 #endif
 
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	show_val_kb(m, "Unaccepted:     ",
+		    global_zone_page_state(NR_UNACCEPTED));
+#endif
+
 	hugetlb_report_meminfo(m);
 
 	arch_report_meminfo(m);
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 72837e019bd1..c5f50ad19870 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -148,6 +148,9 @@ enum zone_stat_item {
 	NR_ZSPAGES,		/* allocated in zsmalloc */
 #endif
 	NR_FREE_CMA_PAGES,
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	NR_UNACCEPTED,
+#endif
 	NR_VM_ZONE_STAT_ITEMS };
 
 enum node_stat_item {
@@ -919,6 +922,11 @@ struct zone {
 	/* free areas of different sizes */
 	struct free_area	free_area[MAX_ORDER + 1];
 
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	/* Pages to be accepted. All pages on the list are MAX_ORDER */
+	struct list_head	unaccepted_pages;
+#endif
+
 	/* zone flags, see below */
 	unsigned long		flags;
 
diff --git a/mm/internal.h b/mm/internal.h
index c05ad651b515..748bfeac1fea 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1114,4 +1114,17 @@ struct vma_prepare {
 	struct vm_area_struct *remove;
 	struct vm_area_struct *remove2;
 };
+
+#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 7911224b1ed3..54f89d9ac98e 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1436,6 +1436,15 @@ phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
 		 */
 		kmemleak_alloc_phys(found, size, 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/mm_init.c b/mm/mm_init.c
index dd3a6ed9663f..5e5afbefda1e 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1373,6 +1373,10 @@ static void __meminit zone_init_free_lists(struct zone *zone)
 		INIT_LIST_HEAD(&zone->free_area[order].free_list[t]);
 		zone->free_area[order].nr_free = 0;
 	}
+
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	INIT_LIST_HEAD(&zone->unaccepted_pages);
+#endif
 }
 
 void __meminit init_currently_empty_zone(struct zone *zone,
@@ -1958,6 +1962,9 @@ static void __init deferred_free_range(unsigned long pfn,
 		return;
 	}
 
+	/* Accept chunks smaller than MAX_ORDER upfront */
+	accept_memory(PFN_PHYS(pfn), PFN_PHYS(pfn + nr_pages));
+
 	for (i = 0; i < nr_pages; i++, page++, pfn++) {
 		if (pageblock_aligned(pfn))
 			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0767dd6bc5ba..d62fcb2f28bd 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -387,6 +387,11 @@ EXPORT_SYMBOL(nr_node_ids);
 EXPORT_SYMBOL(nr_online_nodes);
 #endif
 
+static bool page_contains_unaccepted(struct page *page, unsigned int order);
+static void accept_page(struct page *page, unsigned int order);
+static bool try_to_accept_memory(struct zone *zone, unsigned int order);
+static bool __free_unaccepted(struct page *page);
+
 int page_group_by_mobility_disabled __read_mostly;
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
@@ -1481,6 +1486,13 @@ void __free_pages_core(struct page *page, unsigned int order)
 
 	atomic_long_add(nr_pages, &page_zone(page)->managed_pages);
 
+	if (page_contains_unaccepted(page, order)) {
+		if (order == MAX_ORDER && __free_unaccepted(page))
+			return;
+
+		accept_page(page, order);
+	}
+
 	/*
 	 * Bypass PCP and place fresh pages right to the tail, primarily
 	 * relevant for memory onlining.
@@ -3150,6 +3162,9 @@ static inline long __zone_watermark_unusable_free(struct zone *z,
 	if (!(alloc_flags & ALLOC_CMA))
 		unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES);
 #endif
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	unusable_free += zone_page_state(z, NR_UNACCEPTED);
+#endif
 
 	return unusable_free;
 }
@@ -3449,6 +3464,9 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 				       gfp_mask)) {
 			int ret;
 
+			if (try_to_accept_memory(zone, order))
+				goto try_this_zone;
+
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 			/*
 			 * Watermark failed for this zone, but see if we can
@@ -3501,6 +3519,9 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 
 			return page;
 		} else {
+			if (try_to_accept_memory(zone, order))
+				goto try_this_zone;
+
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 			/* Try again if zone has deferred pages */
 			if (deferred_pages_enabled()) {
@@ -7184,3 +7205,143 @@ bool has_managed_dma(void)
 	return false;
 }
 #endif /* CONFIG_ZONE_DMA */
+
+#ifdef CONFIG_UNACCEPTED_MEMORY
+
+/* Counts number of zones with unaccepted pages. */
+static DEFINE_STATIC_KEY_FALSE(zones_with_unaccepted_pages);
+
+static bool lazy_accept = true;
+
+static int __init accept_memory_parse(char *p)
+{
+	if (!strcmp(p, "lazy")) {
+		lazy_accept = true;
+		return 0;
+	} else if (!strcmp(p, "eager")) {
+		lazy_accept = false;
+		return 0;
+	} else {
+		return -EINVAL;
+	}
+}
+early_param("accept_memory", accept_memory_parse);
+
+static bool page_contains_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);
+}
+
+static void accept_page(struct page *page, unsigned int order)
+{
+	phys_addr_t start = page_to_phys(page);
+
+	accept_memory(start, start + (PAGE_SIZE << order));
+}
+
+static bool try_to_accept_memory_one(struct zone *zone)
+{
+	unsigned long flags;
+	struct page *page;
+	bool last;
+
+	if (list_empty(&zone->unaccepted_pages))
+		return false;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	page = list_first_entry_or_null(&zone->unaccepted_pages,
+					struct page, lru);
+	if (!page) {
+		spin_unlock_irqrestore(&zone->lock, flags);
+		return false;
+	}
+
+	list_del(&page->lru);
+	last = list_empty(&zone->unaccepted_pages);
+
+	__mod_zone_freepage_state(zone, -MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
+	__mod_zone_page_state(zone, NR_UNACCEPTED, -MAX_ORDER_NR_PAGES);
+	spin_unlock_irqrestore(&zone->lock, flags);
+
+	accept_page(page, MAX_ORDER);
+
+	__free_pages_ok(page, MAX_ORDER, FPI_TO_TAIL);
+
+	if (last)
+		static_branch_dec(&zones_with_unaccepted_pages);
+
+	return true;
+}
+
+static bool try_to_accept_memory(struct zone *zone, unsigned int order)
+{
+	long to_accept;
+	int ret = false;
+
+	if (!static_branch_unlikely(&zones_with_unaccepted_pages))
+		return false;
+
+	/* How much to accept to get to high watermark? */
+	to_accept = high_wmark_pages(zone) -
+		    (zone_page_state(zone, NR_FREE_PAGES) -
+		    __zone_watermark_unusable_free(zone, order, 0));
+
+	/* Accept at least one page */
+	do {
+		if (!try_to_accept_memory_one(zone))
+			break;
+		ret = true;
+		to_accept -= MAX_ORDER_NR_PAGES;
+	} while (to_accept > 0);
+
+	return ret;
+}
+
+static bool __free_unaccepted(struct page *page)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long flags;
+	bool first = false;
+
+	if (!lazy_accept)
+		return false;
+
+	spin_lock_irqsave(&zone->lock, flags);
+	first = list_empty(&zone->unaccepted_pages);
+	list_add_tail(&page->lru, &zone->unaccepted_pages);
+	__mod_zone_freepage_state(zone, MAX_ORDER_NR_PAGES, MIGRATE_MOVABLE);
+	__mod_zone_page_state(zone, NR_UNACCEPTED, MAX_ORDER_NR_PAGES);
+	spin_unlock_irqrestore(&zone->lock, flags);
+
+	if (first)
+		static_branch_inc(&zones_with_unaccepted_pages);
+
+	return true;
+}
+
+#else
+
+static bool page_contains_unaccepted(struct page *page, unsigned int order)
+{
+	return false;
+}
+
+static void accept_page(struct page *page, unsigned int order)
+{
+}
+
+static bool try_to_accept_memory(struct zone *zone, unsigned int order)
+{
+	return false;
+}
+
+static bool __free_unaccepted(struct page *page)
+{
+	BUILD_BUG();
+	return false;
+}
+
+#endif /* CONFIG_UNACCEPTED_MEMORY */
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 0a6d742322db..16ec8b994ef3 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1256,6 +1256,9 @@ const char * const vmstat_text[] = {
 	"nr_zspages",
 #endif
 	"nr_free_cma",
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	"nr_unaccepted",
+#endif
 
 	/* enum numa_stat_item counters */
 #ifdef CONFIG_NUMA
-- 
2.39.2

Re: [PATCHv9 02/14] mm: Add support for unaccepted memory

[Vlastimil Babka]

On 3/30/23 13:49, 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.
> 
> The patch implements #1 and #2 for now. #2 is the default. Some
> workloads may want to use #1 with accept_memory=eager in kernel
> command line. #3 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. New memory gets accepted
> before putting pages on free lists. It is done lazily: only accept new
> pages when we run out of already accepted memory. The memory gets
> accepted until the high watermark is reached.

Great.

> Architecture has to provide two helpers if it wants to support
> unaccepted memory:
> 
>  - accept_memory() makes a range of physical addresses accepted.
> 
>  - range_contains_unaccepted_memory() 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

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

Just a small suggestion below:

> +
> +static bool try_to_accept_memory(struct zone *zone, unsigned int order)
> +{
> +	long to_accept;
> +	int ret = false;
> +
> +	if (!static_branch_unlikely(&zones_with_unaccepted_pages))
> +		return false;


This potentially (depends on what compiler decides) means we'll call this
function just to skip the static branch. OTOH forcing it as inline would be
wasteful too. So I'd split that away and make the callers do that static
branch check inline. Just as deferred_pages_enabled() is used.

> +	/* How much to accept to get to high watermark? */
> +	to_accept = high_wmark_pages(zone) -
> +		    (zone_page_state(zone, NR_FREE_PAGES) -
> +		    __zone_watermark_unusable_free(zone, order, 0));
> +
> +	/* Accept at least one page */
> +	do {
> +		if (!try_to_accept_memory_one(zone))
> +			break;
> +		ret = true;
> +		to_accept -= MAX_ORDER_NR_PAGES;
> +	} while (to_accept > 0);
> +
> +	return ret;
> +}

Re: [PATCHv9 02/14] mm: Add support for unaccepted memory

[Kirill A. Shutemov]

On Mon, Apr 03, 2023 at 11:26:53AM +0200, Vlastimil Babka wrote:
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > Acked-by: Mike Rapoport <rppt@linux.ibm.com>	# memblock
> 
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

Thanks!

> Just a small suggestion below:
> 
> > +
> > +static bool try_to_accept_memory(struct zone *zone, unsigned int order)
> > +{
> > +	long to_accept;
> > +	int ret = false;
> > +
> > +	if (!static_branch_unlikely(&zones_with_unaccepted_pages))
> > +		return false;
> 
> 
> This potentially (depends on what compiler decides) means we'll call this
> function just to skip the static branch. OTOH forcing it as inline would be
> wasteful too. So I'd split that away and make the callers do that static
> branch check inline. Just as deferred_pages_enabled() is used.

Like this?

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 07e16e9b49c4..80fe5e4b6cca 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -390,6 +390,7 @@ EXPORT_SYMBOL(nr_online_nodes);
 static bool page_contains_unaccepted(struct page *page, unsigned int order);
 static void accept_page(struct page *page, unsigned int order);
 static bool try_to_accept_memory(struct zone *zone, unsigned int order);
+static inline bool has_unaccepted_memory(void);
 static bool __free_unaccepted(struct page *page);
 
 int page_group_by_mobility_disabled __read_mostly;
@@ -3464,8 +3465,10 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 				       gfp_mask)) {
 			int ret;
 
-			if (try_to_accept_memory(zone, order))
-				goto try_this_zone;
+			if (has_unaccepted_memory()) {
+				if (try_to_accept_memory(zone, order))
+					goto try_this_zone;
+			}
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 			/*
@@ -3519,8 +3522,10 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 
 			return page;
 		} else {
-			if (try_to_accept_memory(zone, order))
-				goto try_this_zone;
+			if (has_unaccepted_memory()) {
+				if (try_to_accept_memory(zone, order))
+					goto try_this_zone;
+			}
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 			/* Try again if zone has deferred pages */
@@ -7302,9 +7307,6 @@ static bool try_to_accept_memory(struct zone *zone, unsigned int order)
 	long to_accept;
 	int ret = false;
 
-	if (!static_branch_unlikely(&zones_with_unaccepted_pages))
-		return false;
-
 	/* How much to accept to get to high watermark? */
 	to_accept = high_wmark_pages(zone) -
 		    (zone_page_state(zone, NR_FREE_PAGES) -
@@ -7321,6 +7323,11 @@ static bool try_to_accept_memory(struct zone *zone, unsigned int order)
 	return ret;
 }
 
+static inline bool has_unaccepted_memory(void)
+{
+	return static_branch_unlikely(&zones_with_unaccepted_pages);
+}
+
 static bool __free_unaccepted(struct page *page)
 {
 	struct zone *zone = page_zone(page);
@@ -7398,6 +7405,11 @@ static bool try_to_accept_memory(struct zone *zone, unsigned int order)
 	return false;
 }
 
+static inline bool has_unaccepted_memory(void)
+{
+	return false;
+}
+
 static bool __free_unaccepted(struct page *page)
 {
 	BUILD_BUG();
-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [PATCHv9 02/14] mm: Add support for unaccepted memory

[Vlastimil Babka]

On 4/3/23 12:02, Kirill A. Shutemov wrote:
> On Mon, Apr 03, 2023 at 11:26:53AM +0200, Vlastimil Babka wrote:
>> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>> > Acked-by: Mike Rapoport <rppt@linux.ibm.com>	# memblock
>> 
>> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> 
> Thanks!
> 
>> Just a small suggestion below:
>> 
>> > +
>> > +static bool try_to_accept_memory(struct zone *zone, unsigned int order)
>> > +{
>> > +	long to_accept;
>> > +	int ret = false;
>> > +
>> > +	if (!static_branch_unlikely(&zones_with_unaccepted_pages))
>> > +		return false;
>> 
>> 
>> This potentially (depends on what compiler decides) means we'll call this
>> function just to skip the static branch. OTOH forcing it as inline would be
>> wasteful too. So I'd split that away and make the callers do that static
>> branch check inline. Just as deferred_pages_enabled() is used.
> 
> Like this?

Yep.

> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 07e16e9b49c4..80fe5e4b6cca 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -390,6 +390,7 @@ EXPORT_SYMBOL(nr_online_nodes);
>  static bool page_contains_unaccepted(struct page *page, unsigned int order);
>  static void accept_page(struct page *page, unsigned int order);
>  static bool try_to_accept_memory(struct zone *zone, unsigned int order);
> +static inline bool has_unaccepted_memory(void);
>  static bool __free_unaccepted(struct page *page);
>  
>  int page_group_by_mobility_disabled __read_mostly;
> @@ -3464,8 +3465,10 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>  				       gfp_mask)) {
>  			int ret;
>  
> -			if (try_to_accept_memory(zone, order))
> -				goto try_this_zone;
> +			if (has_unaccepted_memory()) {
> +				if (try_to_accept_memory(zone, order))
> +					goto try_this_zone;
> +			}
>  
>  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
>  			/*
> @@ -3519,8 +3522,10 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>  
>  			return page;
>  		} else {
> -			if (try_to_accept_memory(zone, order))
> -				goto try_this_zone;
> +			if (has_unaccepted_memory()) {
> +				if (try_to_accept_memory(zone, order))
> +					goto try_this_zone;
> +			}
>  
>  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
>  			/* Try again if zone has deferred pages */
> @@ -7302,9 +7307,6 @@ static bool try_to_accept_memory(struct zone *zone, unsigned int order)
>  	long to_accept;
>  	int ret = false;
>  
> -	if (!static_branch_unlikely(&zones_with_unaccepted_pages))
> -		return false;
> -
>  	/* How much to accept to get to high watermark? */
>  	to_accept = high_wmark_pages(zone) -
>  		    (zone_page_state(zone, NR_FREE_PAGES) -
> @@ -7321,6 +7323,11 @@ static bool try_to_accept_memory(struct zone *zone, unsigned int order)
>  	return ret;
>  }
>  
> +static inline bool has_unaccepted_memory(void)
> +{
> +	return static_branch_unlikely(&zones_with_unaccepted_pages);
> +}
> +
>  static bool __free_unaccepted(struct page *page)
>  {
>  	struct zone *zone = page_zone(page);
> @@ -7398,6 +7405,11 @@ static bool try_to_accept_memory(struct zone *zone, unsigned int order)
>  	return false;
>  }
>  
> +static inline bool has_unaccepted_memory(void)
> +{
> +	return false;
> +}
> +
>  static bool __free_unaccepted(struct page *page)
>  {
>  	BUILD_BUG();

[PATCHv9 03/14] mm/page_alloc: Fake unaccepted memory

[Kirill A. Shutemov]

For testing purposes, it is useful to fake unaccepted memory in the
system. It helps to understand unaccepted memory overhead to the page
allocator.

The patch allows to treat memory above the specified physical memory
address as unaccepted.

The change only fakes unaccepted memory for page allocator. Memblock is
not affected.

It also assumes that arch-provided accept_memory() on already accepted
memory is a nop.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/page_alloc.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d62fcb2f28bd..509a93b7e5af 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7213,6 +7213,8 @@ static DEFINE_STATIC_KEY_FALSE(zones_with_unaccepted_pages);
 
 static bool lazy_accept = true;
 
+static unsigned long fake_unaccepted_start = -1UL;
+
 static int __init accept_memory_parse(char *p)
 {
 	if (!strcmp(p, "lazy")) {
@@ -7227,11 +7229,30 @@ static int __init accept_memory_parse(char *p)
 }
 early_param("accept_memory", accept_memory_parse);
 
+static int __init fake_unaccepted_start_parse(char *p)
+{
+	if (!p)
+		return -EINVAL;
+
+	fake_unaccepted_start = memparse(p, &p);
+
+	if (*p != '\0') {
+		fake_unaccepted_start = -1UL;
+		return -EINVAL;
+	}
+
+	return 0;
+}
+early_param("fake_unaccepted_start", fake_unaccepted_start_parse);
+
 static bool page_contains_unaccepted(struct page *page, unsigned int order)
 {
 	phys_addr_t start = page_to_phys(page);
 	phys_addr_t end = start + (PAGE_SIZE << order);
 
+	if (start >= fake_unaccepted_start)
+		return true;
+
 	return range_contains_unaccepted_memory(start, end);
 }
 
-- 
2.39.2

Re: [PATCHv9 03/14] mm/page_alloc: Fake unaccepted memory

[Vlastimil Babka]

On 3/30/23 13:49, Kirill A. Shutemov wrote:
> For testing purposes, it is useful to fake unaccepted memory in the
> system. It helps to understand unaccepted memory overhead to the page
> allocator.

Ack on being useful for testing, but the question is if we want to also
merge this patch into mainline as it is?

> The patch allows to treat memory above the specified physical memory
> address as unaccepted.
> 
> The change only fakes unaccepted memory for page allocator. Memblock is
> not affected.
> 
> It also assumes that arch-provided accept_memory() on already accepted
> memory is a nop.

I guess to be in mainline it would have to at least gracefully handle the
case of accept_memory actually not being a nop, and running on a system with
actual unaccepted memory (probably by ignoring the parameter in such case).
Then also the parameter would have to be documented.

Speaking of documented parameters, I found at least two that seem a more
generic variant of this (but I didn't look closely if that makes sense):

efi_fake_mem=   nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
    Add arbitrary attribute to specific memory range by
    updating original EFI memory map.

memmap=<size>%<offset>-<oldtype>+<newtype>
    [KNL,ACPI] Convert memory within the specified region
    from <oldtype> to <newtype>. If "-<oldtype>" is left

Would any of those be usable for this usecase?

> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
>  mm/page_alloc.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index d62fcb2f28bd..509a93b7e5af 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7213,6 +7213,8 @@ static DEFINE_STATIC_KEY_FALSE(zones_with_unaccepted_pages);
>  
>  static bool lazy_accept = true;
>  
> +static unsigned long fake_unaccepted_start = -1UL;
> +
>  static int __init accept_memory_parse(char *p)
>  {
>  	if (!strcmp(p, "lazy")) {
> @@ -7227,11 +7229,30 @@ static int __init accept_memory_parse(char *p)
>  }
>  early_param("accept_memory", accept_memory_parse);
>  
> +static int __init fake_unaccepted_start_parse(char *p)
> +{
> +	if (!p)
> +		return -EINVAL;
> +
> +	fake_unaccepted_start = memparse(p, &p);
> +
> +	if (*p != '\0') {
> +		fake_unaccepted_start = -1UL;
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +early_param("fake_unaccepted_start", fake_unaccepted_start_parse);
> +
>  static bool page_contains_unaccepted(struct page *page, unsigned int order)
>  {
>  	phys_addr_t start = page_to_phys(page);
>  	phys_addr_t end = start + (PAGE_SIZE << order);
>  
> +	if (start >= fake_unaccepted_start)
> +		return true;
> +
>  	return range_contains_unaccepted_memory(start, end);
>  }
>  

Re: [PATCHv9 03/14] mm/page_alloc: Fake unaccepted memory

[Kirill A. Shutemov]

On Mon, Apr 03, 2023 at 03:39:53PM +0200, Vlastimil Babka wrote:
> On 3/30/23 13:49, Kirill A. Shutemov wrote:
> > For testing purposes, it is useful to fake unaccepted memory in the
> > system. It helps to understand unaccepted memory overhead to the page
> > allocator.
> 
> Ack on being useful for testing, but the question is if we want to also
> merge this patch into mainline as it is?

I don't insist on getting it upstream, but it can be handy to debug
related bugs in the future.

> > The patch allows to treat memory above the specified physical memory
> > address as unaccepted.
> > 
> > The change only fakes unaccepted memory for page allocator. Memblock is
> > not affected.
> > 
> > It also assumes that arch-provided accept_memory() on already accepted
> > memory is a nop.
> 
> I guess to be in mainline it would have to at least gracefully handle the
> case of accept_memory actually not being a nop, and running on a system with
> actual unaccepted memory (probably by ignoring the parameter in such case).
> Then also the parameter would have to be documented.

As it is written now, accept_memory() is nop on system with real
unaccepted memory if the memory is already accepted. Arch-specific code
will check against own records to see if the memory needs accepting. If
not, just return.

And the option will not interfere with unaccepted memory declared by EFI
memmap. It can extend it, but that's it.

Looks safe to me.

> Speaking of documented parameters, I found at least two that seem a more
> generic variant of this (but I didn't look closely if that makes sense):
> 
> efi_fake_mem=   nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>     Add arbitrary attribute to specific memory range by
>     updating original EFI memory map.
> 
> memmap=<size>%<offset>-<oldtype>+<newtype>
>     [KNL,ACPI] Convert memory within the specified region
>     from <oldtype> to <newtype>. If "-<oldtype>" is left
> 
> Would any of those be usable for this usecase?

Oh. I missed them. Will take a closer look.

> 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > ---
> >  mm/page_alloc.c | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> > 
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index d62fcb2f28bd..509a93b7e5af 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -7213,6 +7213,8 @@ static DEFINE_STATIC_KEY_FALSE(zones_with_unaccepted_pages);
> >  
> >  static bool lazy_accept = true;
> >  
> > +static unsigned long fake_unaccepted_start = -1UL;
> > +
> >  static int __init accept_memory_parse(char *p)
> >  {
> >  	if (!strcmp(p, "lazy")) {
> > @@ -7227,11 +7229,30 @@ static int __init accept_memory_parse(char *p)
> >  }
> >  early_param("accept_memory", accept_memory_parse);
> >  
> > +static int __init fake_unaccepted_start_parse(char *p)
> > +{
> > +	if (!p)
> > +		return -EINVAL;
> > +
> > +	fake_unaccepted_start = memparse(p, &p);
> > +
> > +	if (*p != '\0') {
> > +		fake_unaccepted_start = -1UL;
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +early_param("fake_unaccepted_start", fake_unaccepted_start_parse);
> > +
> >  static bool page_contains_unaccepted(struct page *page, unsigned int order)
> >  {
> >  	phys_addr_t start = page_to_phys(page);
> >  	phys_addr_t end = start + (PAGE_SIZE << order);
> >  
> > +	if (start >= fake_unaccepted_start)
> > +		return true;
> > +
> >  	return range_contains_unaccepted_memory(start, end);
> >  }
> >  
> 

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [PATCHv9 03/14] mm/page_alloc: Fake unaccepted memory

[Kirill A. Shutemov]

On Mon, Apr 03, 2023 at 05:39:15PM +0300, Kirill A. Shutemov wrote:
> On Mon, Apr 03, 2023 at 03:39:53PM +0200, Vlastimil Babka wrote:
> > On 3/30/23 13:49, Kirill A. Shutemov wrote:
> > > For testing purposes, it is useful to fake unaccepted memory in the
> > > system. It helps to understand unaccepted memory overhead to the page
> > > allocator.
> > 
> > Ack on being useful for testing, but the question is if we want to also
> > merge this patch into mainline as it is?
> 
> I don't insist on getting it upstream, but it can be handy to debug
> related bugs in the future.
> 
> > > The patch allows to treat memory above the specified physical memory
> > > address as unaccepted.
> > > 
> > > The change only fakes unaccepted memory for page allocator. Memblock is
> > > not affected.
> > > 
> > > It also assumes that arch-provided accept_memory() on already accepted
> > > memory is a nop.
> > 
> > I guess to be in mainline it would have to at least gracefully handle the
> > case of accept_memory actually not being a nop, and running on a system with
> > actual unaccepted memory (probably by ignoring the parameter in such case).
> > Then also the parameter would have to be documented.
> 
> As it is written now, accept_memory() is nop on system with real
> unaccepted memory if the memory is already accepted. Arch-specific code
> will check against own records to see if the memory needs accepting. If
> not, just return.
> 
> And the option will not interfere with unaccepted memory declared by EFI
> memmap. It can extend it, but that's it.
> 
> Looks safe to me.
> 
> > Speaking of documented parameters, I found at least two that seem a more
> > generic variant of this (but I didn't look closely if that makes sense):
> > 
> > efi_fake_mem=   nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
> >     Add arbitrary attribute to specific memory range by
> >     updating original EFI memory map.

As of now, efi_fake_mem= can adjust attributes of memory. Unaccepted is
type of memory, not an attribute. I guess we can allow it override type
too. But syntax is going to be fun.

> > memmap=<size>%<offset>-<oldtype>+<newtype>
> >     [KNL,ACPI] Convert memory within the specified region
> >     from <oldtype> to <newtype>. If "-<oldtype>" is left

It overrides E820 map, but unaccepted memory is not represented there.
Unaccepted memory is just RAM in E820.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [PATCHv9 03/14] mm/page_alloc: Fake unaccepted memory

[Kirill A. Shutemov]

On Mon, Apr 03, 2023 at 06:50:11PM +0300, Kirill A. Shutemov wrote:
> On Mon, Apr 03, 2023 at 05:39:15PM +0300, Kirill A. Shutemov wrote:
> > On Mon, Apr 03, 2023 at 03:39:53PM +0200, Vlastimil Babka wrote:
> > > On 3/30/23 13:49, Kirill A. Shutemov wrote:
> > > > For testing purposes, it is useful to fake unaccepted memory in the
> > > > system. It helps to understand unaccepted memory overhead to the page
> > > > allocator.
> > > 
> > > Ack on being useful for testing, but the question is if we want to also
> > > merge this patch into mainline as it is?
> > 
> > I don't insist on getting it upstream, but it can be handy to debug
> > related bugs in the future.
> > 
> > > > The patch allows to treat memory above the specified physical memory
> > > > address as unaccepted.
> > > > 
> > > > The change only fakes unaccepted memory for page allocator. Memblock is
> > > > not affected.
> > > > 
> > > > It also assumes that arch-provided accept_memory() on already accepted
> > > > memory is a nop.
> > > 
> > > I guess to be in mainline it would have to at least gracefully handle the
> > > case of accept_memory actually not being a nop, and running on a system with
> > > actual unaccepted memory (probably by ignoring the parameter in such case).
> > > Then also the parameter would have to be documented.
> > 
> > As it is written now, accept_memory() is nop on system with real
> > unaccepted memory if the memory is already accepted. Arch-specific code
> > will check against own records to see if the memory needs accepting. If
> > not, just return.
> > 
> > And the option will not interfere with unaccepted memory declared by EFI
> > memmap. It can extend it, but that's it.
> > 
> > Looks safe to me.
> > 
> > > Speaking of documented parameters, I found at least two that seem a more
> > > generic variant of this (but I didn't look closely if that makes sense):
> > > 
> > > efi_fake_mem=   nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
> > >     Add arbitrary attribute to specific memory range by
> > >     updating original EFI memory map.
> 
> As of now, efi_fake_mem= can adjust attributes of memory. Unaccepted is
> type of memory, not an attribute. I guess we can allow it override type
> too. But syntax is going to be fun.

efi_fake_mem applied too late. Bitmap that represents unaccepted memory
for kernel created at kernel decompression stage, but efi_fake_mem=
handled in main kernel.

I don't think pushing efi_fake_mem to decompressor makes sesne. I would
rather drom the feature altogether.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [PATCHv9 03/14] mm/page_alloc: Fake unaccepted memory

[David Hildenbrand]

On 30.03.23 13:49, Kirill A. Shutemov wrote:
> For testing purposes, it is useful to fake unaccepted memory in the
> system. It helps to understand unaccepted memory overhead to the page
> allocator.
> 
> The patch allows to treat memory above the specified physical memory
> address as unaccepted.
> 
> The change only fakes unaccepted memory for page allocator. Memblock is
> not affected.
> 
> It also assumes that arch-provided accept_memory() on already accepted
> memory is a nop.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
>   mm/page_alloc.c | 21 +++++++++++++++++++++
>   1 file changed, 21 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index d62fcb2f28bd..509a93b7e5af 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7213,6 +7213,8 @@ static DEFINE_STATIC_KEY_FALSE(zones_with_unaccepted_pages);
>   
>   static bool lazy_accept = true;
>   
> +static unsigned long fake_unaccepted_start = -1UL;
> +
>   static int __init accept_memory_parse(char *p)
>   {
>   	if (!strcmp(p, "lazy")) {
> @@ -7227,11 +7229,30 @@ static int __init accept_memory_parse(char *p)
>   }
>   early_param("accept_memory", accept_memory_parse);
>   
> +static int __init fake_unaccepted_start_parse(char *p)
> +{
> +	if (!p)
> +		return -EINVAL;
> +
> +	fake_unaccepted_start = memparse(p, &p);
> +
> +	if (*p != '\0') {
> +		fake_unaccepted_start = -1UL;
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +early_param("fake_unaccepted_start", fake_unaccepted_start_parse);
> +
>   static bool page_contains_unaccepted(struct page *page, unsigned int order)
>   {
>   	phys_addr_t start = page_to_phys(page);
>   	phys_addr_t end = start + (PAGE_SIZE << order);
>   
> +	if (start >= fake_unaccepted_start)
> +		return true;
> +
>   	return range_contains_unaccepted_memory(start, end);
>   }
>   

The "unpleasant" thing about this is, that page_contains_unaccepted() 
could not be used for sanity checks because the result is static.

For example, something like

if (page_contains_unaccepted(page, 0))
	accept_memory(page, 0);
BUG_ON(!page_contains_unaccepted(page, 0));

Would work on real hardware, however, not for the fake variant.

-- 
Thanks,

David / dhildenb

Re: [PATCHv9 03/14] mm/page_alloc: Fake unaccepted memory

[Kirill A. Shutemov]

On Mon, Apr 03, 2023 at 04:43:08PM +0200, David Hildenbrand wrote:
> On 30.03.23 13:49, Kirill A. Shutemov wrote:
> > For testing purposes, it is useful to fake unaccepted memory in the
> > system. It helps to understand unaccepted memory overhead to the page
> > allocator.
> > 
> > The patch allows to treat memory above the specified physical memory
> > address as unaccepted.
> > 
> > The change only fakes unaccepted memory for page allocator. Memblock is
> > not affected.
> > 
> > It also assumes that arch-provided accept_memory() on already accepted
> > memory is a nop.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > ---
> >   mm/page_alloc.c | 21 +++++++++++++++++++++
> >   1 file changed, 21 insertions(+)
> > 
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index d62fcb2f28bd..509a93b7e5af 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -7213,6 +7213,8 @@ static DEFINE_STATIC_KEY_FALSE(zones_with_unaccepted_pages);
> >   static bool lazy_accept = true;
> > +static unsigned long fake_unaccepted_start = -1UL;
> > +
> >   static int __init accept_memory_parse(char *p)
> >   {
> >   	if (!strcmp(p, "lazy")) {
> > @@ -7227,11 +7229,30 @@ static int __init accept_memory_parse(char *p)
> >   }
> >   early_param("accept_memory", accept_memory_parse);
> > +static int __init fake_unaccepted_start_parse(char *p)
> > +{
> > +	if (!p)
> > +		return -EINVAL;
> > +
> > +	fake_unaccepted_start = memparse(p, &p);
> > +
> > +	if (*p != '\0') {
> > +		fake_unaccepted_start = -1UL;
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +early_param("fake_unaccepted_start", fake_unaccepted_start_parse);
> > +
> >   static bool page_contains_unaccepted(struct page *page, unsigned int order)
> >   {
> >   	phys_addr_t start = page_to_phys(page);
> >   	phys_addr_t end = start + (PAGE_SIZE << order);
> > +	if (start >= fake_unaccepted_start)
> > +		return true;
> > +
> >   	return range_contains_unaccepted_memory(start, end);
> >   }
> 
> The "unpleasant" thing about this is, that page_contains_unaccepted() could
> not be used for sanity checks because the result is static.
> 
> For example, something like
> 
> if (page_contains_unaccepted(page, 0))
> 	accept_memory(page, 0);
> BUG_ON(!page_contains_unaccepted(page, 0));
> 
> Would work on real hardware, however, not for the fake variant.

Need for raw_page_contains_unaccepted()? :P

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

[PATCHv9 04/14] mm/page_alloc: Add sysfs handle to accept accept_memory

[Kirill A. Shutemov]

Write amount of memory to accept into the new sysfs handle
/sys/kernel/mm/page_alloc/accept_memory.

Write 'all' to the handle to accept all memory in the system.

It can be used to implement background memory accepting from userspace.
It is also useful for debugging.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/page_alloc.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 509a93b7e5af..07e16e9b49c4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7343,6 +7343,45 @@ static bool __free_unaccepted(struct page *page)
 	return true;
 }
 
+static ssize_t accept_memory_store(struct kobject *kobj,
+				    struct kobj_attribute *attr,
+				    const char *buf, size_t count)
+{
+	unsigned long to_accept = 0;
+	struct zone *zone;
+	char *retptr;
+
+	if (sysfs_streq(buf, "all")) {
+		to_accept = ULONG_MAX;
+	} else {
+		to_accept = memparse(buf, &retptr);
+
+		/* Get rid of trailing whitespace, including '\n' */
+		retptr = skip_spaces(retptr);
+
+		if (*retptr != 0 || to_accept == 0)
+			return -EINVAL;
+	}
+
+	for_each_populated_zone(zone) {
+		while (try_to_accept_memory_one(zone)) {
+			if (to_accept <= PAGE_SIZE << MAX_ORDER)
+				return count;
+
+			to_accept -= PAGE_SIZE << MAX_ORDER;
+		}
+	}
+
+	return count;
+}
+
+static struct kobj_attribute accept_memory_attr = __ATTR_WO(accept_memory);
+
+static struct attribute *page_alloc_attr[] = {
+	&accept_memory_attr.attr,
+	NULL
+};
+
 #else
 
 static bool page_contains_unaccepted(struct page *page, unsigned int order)
@@ -7366,3 +7405,28 @@ static bool __free_unaccepted(struct page *page)
 }
 
 #endif /* CONFIG_UNACCEPTED_MEMORY */
+
+static const struct attribute_group page_alloc_attr_group = {
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	.attrs = page_alloc_attr,
+#endif
+};
+
+static int __init page_alloc_init_sysfs(void)
+{
+	struct kobject *page_alloc_kobj;
+	int err;
+
+	page_alloc_kobj = kobject_create_and_add("page_alloc", mm_kobj);
+	if (!page_alloc_kobj)
+		return -ENOMEM;
+
+	err = sysfs_create_group(page_alloc_kobj, &page_alloc_attr_group);
+	if (err) {
+		kobject_put(page_alloc_kobj);
+		return err;
+	}
+
+	return 0;
+}
+late_initcall(page_alloc_init_sysfs);
-- 
2.39.2

Re: [PATCHv9 04/14] mm/page_alloc: Add sysfs handle to accept accept_memory

[Vlastimil Babka]

On 3/30/23 13:49, Kirill A. Shutemov wrote:
> Write amount of memory to accept into the new sysfs handle
> /sys/kernel/mm/page_alloc/accept_memory.
> 
> Write 'all' to the handle to accept all memory in the system.
> 
> It can be used to implement background memory accepting from userspace.
> It is also useful for debugging.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Somewhat similarly to patch 3, I'd think we don't need this patch in
mainline without clear usecases first, although it's good to post for
testing/debugging.

> ---
>  mm/page_alloc.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 64 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 509a93b7e5af..07e16e9b49c4 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7343,6 +7343,45 @@ static bool __free_unaccepted(struct page *page)
>  	return true;
>  }
>  
> +static ssize_t accept_memory_store(struct kobject *kobj,
> +				    struct kobj_attribute *attr,
> +				    const char *buf, size_t count)
> +{
> +	unsigned long to_accept = 0;
> +	struct zone *zone;
> +	char *retptr;
> +
> +	if (sysfs_streq(buf, "all")) {
> +		to_accept = ULONG_MAX;
> +	} else {
> +		to_accept = memparse(buf, &retptr);
> +
> +		/* Get rid of trailing whitespace, including '\n' */
> +		retptr = skip_spaces(retptr);
> +
> +		if (*retptr != 0 || to_accept == 0)
> +			return -EINVAL;
> +	}
> +
> +	for_each_populated_zone(zone) {
> +		while (try_to_accept_memory_one(zone)) {
> +			if (to_accept <= PAGE_SIZE << MAX_ORDER)
> +				return count;
> +
> +			to_accept -= PAGE_SIZE << MAX_ORDER;
> +		}
> +	}
> +
> +	return count;
> +}
> +
> +static struct kobj_attribute accept_memory_attr = __ATTR_WO(accept_memory);
> +
> +static struct attribute *page_alloc_attr[] = {
> +	&accept_memory_attr.attr,
> +	NULL
> +};
> +
>  #else
>  
>  static bool page_contains_unaccepted(struct page *page, unsigned int order)
> @@ -7366,3 +7405,28 @@ static bool __free_unaccepted(struct page *page)
>  }
>  
>  #endif /* CONFIG_UNACCEPTED_MEMORY */
> +
> +static const struct attribute_group page_alloc_attr_group = {
> +#ifdef CONFIG_UNACCEPTED_MEMORY
> +	.attrs = page_alloc_attr,
> +#endif
> +};
> +
> +static int __init page_alloc_init_sysfs(void)
> +{
> +	struct kobject *page_alloc_kobj;
> +	int err;
> +
> +	page_alloc_kobj = kobject_create_and_add("page_alloc", mm_kobj);
> +	if (!page_alloc_kobj)
> +		return -ENOMEM;
> +
> +	err = sysfs_create_group(page_alloc_kobj, &page_alloc_attr_group);
> +	if (err) {
> +		kobject_put(page_alloc_kobj);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +late_initcall(page_alloc_init_sysfs);

Re: [PATCHv9 04/14] mm/page_alloc: Add sysfs handle to accept accept_memory

[Kirill A. Shutemov]

On Mon, Apr 03, 2023 at 03:43:32PM +0200, Vlastimil Babka wrote:
> On 3/30/23 13:49, Kirill A. Shutemov wrote:
> > Write amount of memory to accept into the new sysfs handle
> > /sys/kernel/mm/page_alloc/accept_memory.
> > 
> > Write 'all' to the handle to accept all memory in the system.
> > 
> > It can be used to implement background memory accepting from userspace.
> > It is also useful for debugging.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> 
> Somewhat similarly to patch 3, I'd think we don't need this patch in
> mainline without clear usecases first, although it's good to post for
> testing/debugging.

I thought about it as a way to implement #3 from 02/14 commit message:
users who want to accept all memory in background can use the mechanism.

But, again, we can leave out until later.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

[PATCHv9 05/14] efi/x86: Get full memory map in allocate_e820()

[Kirill A. Shutemov]

Currently allocate_e820() is 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.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
---
 drivers/firmware/efi/libstub/x86-stub.c | 26 +++++++++++--------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index a0bfd31358ba..fff81843169c 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -681,28 +681,24 @@ static efi_status_t allocate_e820(struct boot_params *params,
 				  struct setup_data **e820ext,
 				  u32 *e820ext_size)
 {
-	unsigned long map_size, desc_size, map_key;
+	struct efi_boot_memmap *map;
 	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, false);
+	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);
+	return status;
 }
 
 struct exit_boot_struct {
-- 
2.39.2

[PATCHv9 06/14] 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>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 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/find.c          | 54 ++++++++++++++++
 arch/x86/boot/compressed/find.h          | 79 ++++++++++++++++++++++++
 arch/x86/boot/compressed/math.h          | 37 +++++++++++
 arch/x86/boot/compressed/minmax.h        | 61 ++++++++++++++++++
 arch/x86/boot/compressed/pgtable_types.h | 25 ++++++++
 10 files changed, 438 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/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 8518ae214c9b..38badf028543 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/find.c b/arch/x86/boot/compressed/find.c
new file mode 100644
index 000000000000..b97a9e7c8085
--- /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 (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..903574b9d57a
--- /dev/null
+++ b/arch/x86/boot/compressed/find.h
@@ -0,0 +1,79 @@
+/* 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"
+
+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 (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 (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
-- 
2.39.2

[PATCHv9 07/14] 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.

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           | 73 ++++++++++++++++++++++++
 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  | 65 +++++++++++++++++++++
 include/linux/efi.h                      |  3 +-
 9 files changed, 168 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 6b6cfe607bdb..f62c02348f9a 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -107,6 +107,7 @@ 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) += $(obj)/efi.o
 vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_mixed.o
diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
new file mode 100644
index 000000000000..6b15a0ed8b54
--- /dev/null
+++ b/arch/x86/boot/compressed/mem.c
@@ -0,0 +1,73 @@
+// 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.  Take
+ * unaligned start/end addresses and either:
+ *  1. Accepts the memory immediately and in its entirety
+ *  2. Accepts unaligned parts, and marks *some* aligned part unaccepted
+ *
+ * The function will never reach the bitmap_set() with zero bits to set.
+ */
+void process_unaccepted_memory(struct boot_params *params, u64 start, u64 end)
+{
+	/*
+	 * Ensure that at least one bit will be set in the bitmap by
+	 * immediately accepting all regions under 2*PMD_SIZE.  This is
+	 * imprecise and may immediately accept some areas that could
+	 * have been represented in the bitmap.  But, results in simpler
+	 * code below
+	 *
+	 * Consider case like this:
+	 *
+	 * | 4k | 2044k |    2048k   |
+	 * ^ 0x0        ^ 2MB        ^ 4MB
+	 *
+	 * Only the first 4k has been accepted. The 0MB->2MB region can not be
+	 * represented in the bitmap. The 2MB->4MB region can be represented in
+	 * the bitmap. But, the 0MB->4MB region is <2*PMD_SIZE and will be
+	 * immediately accepted in its entirety.
+	 */
+	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 to be marked in the bitmap.
+	 */
+
+	/* 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 01d19fc22346..630a54046af0 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -189,7 +189,7 @@ 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 043ca31c114e..231f1c70d1db 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -269,6 +269,20 @@ config EFI_COCO_SECRET
 	  virt/coco/efi_secret module to access the secrets, which in turn
 	  allows userspace programs to access the injected secrets.
 
+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.
+
 config EFI_EMBEDDED_FIRMWARE
 	bool
 	select CRYPTO_LIB_SHA256
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index abeff7dc0b58..7dce06e419c5 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -843,6 +843,7 @@ 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 fff81843169c..1643ddbde249 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"
 
@@ -613,6 +614,16 @@ 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\nConsider 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;
 		}
@@ -677,6 +688,57 @@ static efi_status_t alloc_e820ext(u32 nr_desc, struct setup_data **e820ext,
 	return status;
 }
 
+static efi_status_t allocate_unaccepted_bitmap(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;
+		unsigned long m = (unsigned long)map->map;
+
+		d = efi_early_memdesc_ptr(m, 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.
+	 *
+	 * 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 setup_data **e820ext,
 				  u32 *e820ext_size)
@@ -697,6 +759,9 @@ 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_bitmap(params, nr_desc, map);
+
 	efi_bs_call(free_pool, map);
 	return status;
 }
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 04a733f0ba95..1d4f0343c710 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 */
-- 
2.39.2

[PATCHv9 08/14] 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 f62c02348f9a..74f7adee46ad 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -107,7 +107,7 @@ 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) += $(obj)/efi.o
 vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_mixed.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 454757fbdfe5..749f0fe7e446 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -672,6 +672,28 @@ 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.
@@ -716,18 +738,7 @@ 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 6b15a0ed8b54..de858a5180b6 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 */
@@ -71,3 +74,18 @@ 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 014ff222bf4b..186bfd53e042 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -455,6 +455,12 @@ 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);
 	entry_offset = parse_elf(output);
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 2f155a0e3041..9663d1839f54 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -247,4 +247,10 @@ 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
-- 
2.39.2

[PATCHv9 09/14] 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 | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index fb8cf953380d..483c36a28d2e 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1316,6 +1316,23 @@ void __init e820__memblock_setup(void)
 	int i;
 	u64 end;
 
+	/*
+	 * Mark unaccepted memory bitmap reserved.
+	 *
+	 * This kind of reservation usually done from early_reserve_memory(),
+	 * but early_reserve_memory() called before e820__memory_setup(), so
+	 * e820_table is not finalized and e820__end_of_ram_pfn() cannot be
+	 * used to get correct RAM size.
+	 */
+	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
-- 
2.39.2

[PATCHv9 10/14] 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.

 - range_contains_unaccepted_memory() checks 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          | 61 ++++++++++++++++++++++++
 4 files changed, 70 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 d18e5c332cb9..4bab2bb2c9c0 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 c80febc44cd2..b0ef1755e5c8 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -67,3 +67,5 @@ 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..1df918b21469
--- /dev/null
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -0,0 +1,61 @@
+// 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;
+	unsigned long flags;
+	bool ret = false;
+
+	if (!boot_params.unaccepted_memory)
+		return 0;
+
+	bitmap = __va(boot_params.unaccepted_memory);
+
+	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;
+}
-- 
2.39.2

[PATCHv9 11/14] 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 range_contains_unaccepted_memory(start, end)
   checks up to end+2M if 'end' is aligned on a 2M boundary. It may
   require checking 2M chunk beyond end of RAM. The bitmap allocation is
   modified to accommodate this.
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>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
---
 arch/x86/mm/unaccepted_memory.c         | 39 +++++++++++++++++++++++++
 drivers/firmware/efi/libstub/x86-stub.c |  7 +++++
 2 files changed, 46 insertions(+)

diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
index 1df918b21469..a0a58486eb74 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. (immediately following this comment)
+	 *
+	 * 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)) {
@@ -46,6 +78,13 @@ bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end)
 
 	bitmap = __va(boot_params.unaccepted_memory);
 
+	/*
+	 * Also consider the unaccepted state of the *next* page. See fix #1 in
+	 * the 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 1643ddbde249..1afe7b5b02e1 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -715,6 +715,13 @@ static efi_status_t allocate_unaccepted_bitmap(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.
-- 
2.39.2

Re: [PATCHv9 11/14] x86/mm: Avoid load_unaligned_zeropad() stepping into unaccepted memory

[Vlastimil Babka]

On 3/30/23 13:49, Kirill A. Shutemov wrote:
> 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. It may
>    require checking 2M chunk beyond end of RAM. The bitmap allocation is
>    modified to accommodate this.
> 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.

At least the part about PageUnaccepted() is obsolete in v9, no?

> This is an actual, real-world problem which was discovered during TDX
> testing.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
> ---
>  arch/x86/mm/unaccepted_memory.c         | 39 +++++++++++++++++++++++++
>  drivers/firmware/efi/libstub/x86-stub.c |  7 +++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
> index 1df918b21469..a0a58486eb74 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. (immediately following this comment)
> +	 *
> +	 * 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.
> +	 */

And here.

> +	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)) {
> @@ -46,6 +78,13 @@ bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end)
>  
>  	bitmap = __va(boot_params.unaccepted_memory);
>  
> +	/*
> +	 * Also consider the unaccepted state of the *next* page. See fix #1 in
> +	 * the 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 1643ddbde249..1afe7b5b02e1 100644
> --- a/drivers/firmware/efi/libstub/x86-stub.c
> +++ b/drivers/firmware/efi/libstub/x86-stub.c
> @@ -715,6 +715,13 @@ static efi_status_t allocate_unaccepted_bitmap(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.

Re: [PATCHv9 11/14] x86/mm: Avoid load_unaligned_zeropad() stepping into unaccepted memory

[Kirill A. Shutemov]

On Mon, Apr 03, 2023 at 03:28:36PM +0200, Vlastimil Babka wrote:
> On 3/30/23 13:49, Kirill A. Shutemov wrote:
> > 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. It may
> >    require checking 2M chunk beyond end of RAM. The bitmap allocation is
> >    modified to accommodate this.
> > 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.
> 
> At least the part about PageUnaccepted() is obsolete in v9, no?

Ah, right. Nice catch.

I removed PageUnaccepted() late in patchset preparation and forgot about
this.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

[PATCHv9 12/14] 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>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
---
 arch/x86/coco/tdx/tdx.c           | 32 -------------------
 arch/x86/include/asm/shared/tdx.h | 51 +++++++++++++++++++++++++++++++
 arch/x86/include/asm/tdx.h        | 19 ------------
 3 files changed, 51 insertions(+), 51 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 055300e08fb3..a9893f44288f 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -14,20 +14,6 @@
 #include <asm/insn-eval.h>
 #include <asm/pgtable.h>
 
-/* TDX module Call Leaf IDs */
-#define TDX_GET_INFO			1
-#define TDX_GET_VEINFO			3
-#define TDX_GET_REPORT			4
-#define TDX_ACCEPT_PAGE			6
-#define TDX_WR				8
-
-/* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */
-#define TDCS_NOTIFY_ENABLES		0x9100000000000010
-
-/* TDX hypercall Leaf IDs */
-#define TDVMCALL_MAP_GPA		0x10001
-#define TDVMCALL_REPORT_FATAL_ERROR	0x10003
-
 /* MMIO direction */
 #define EPT_READ	0
 #define EPT_WRITE	1
@@ -51,24 +37,6 @@
 
 #define TDREPORT_SUBTYPE_0	0
 
-/*
- * 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 */
 noinstr void __tdx_hypercall_failed(void)
 {
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 4a03993e0785..562b3f4cbde8 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -12,6 +12,20 @@
 #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_GET_REPORT			4
+#define TDX_ACCEPT_PAGE			6
+#define TDX_WR				8
+
+/* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */
+#define TDCS_NOTIFY_ENABLES		0x9100000000000010
+
+/* TDX hypercall Leaf IDs */
+#define TDVMCALL_MAP_GPA		0x10001
+#define TDVMCALL_REPORT_FATAL_ERROR	0x10003
+
 #ifndef __ASSEMBLY__
 
 /*
@@ -38,8 +52,45 @@ 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 28d889c9aa16..234197ec17e4 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);
-- 
2.39.2

[PATCHv9 13/14] 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 argument 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>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
---
 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 a9893f44288f..9e6557d7514c 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -713,18 +713,18 @@ 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
@@ -743,15 +743,14 @@ 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;
 }
 
 /*
@@ -788,21 +787,22 @@ 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;
-- 
2.39.2

[PATCHv9 14/14] 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                      |  2 +
 arch/x86/boot/compressed/Makefile     |  2 +-
 arch/x86/boot/compressed/error.c      | 19 ++++++
 arch/x86/boot/compressed/error.h      |  1 +
 arch/x86/boot/compressed/mem.c        | 33 +++++++++-
 arch/x86/boot/compressed/tdx-shared.c |  2 +
 arch/x86/boot/compressed/tdx.c        | 39 +++++++++++
 arch/x86/coco/tdx/Makefile            |  2 +-
 arch/x86/coco/tdx/tdx-shared.c        | 95 +++++++++++++++++++++++++++
 arch/x86/coco/tdx/tdx.c               | 86 +-----------------------
 arch/x86/include/asm/shared/tdx.h     |  2 +
 arch/x86/include/asm/tdx.h            |  2 +
 arch/x86/mm/unaccepted_memory.c       |  9 ++-
 13 files changed, 206 insertions(+), 88 deletions(-)
 create mode 100644 arch/x86/boot/compressed/tdx-shared.c
 create mode 100644 arch/x86/coco/tdx/tdx-shared.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index df21fba77db1..448cd869f0bd 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -884,9 +884,11 @@ config INTEL_TDX_GUEST
 	bool "Intel TDX (Trust Domain Extensions) - Guest Support"
 	depends on X86_64 && CPU_SUP_INTEL
 	depends on X86_X2APIC
+	depends on EFI_STUB
 	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/Makefile b/arch/x86/boot/compressed/Makefile
index 74f7adee46ad..71d9f71c13eb 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -106,7 +106,7 @@ ifdef CONFIG_X86_64
 endif
 
 vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
-vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o $(obj)/tdcall.o
+vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o $(obj)/tdx-shared.o $(obj)/tdcall.o
 vmlinux-objs-$(CONFIG_UNACCEPTED_MEMORY) += $(obj)/bitmap.o $(obj)/find.o $(obj)/mem.o
 
 vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
diff --git a/arch/x86/boot/compressed/error.c b/arch/x86/boot/compressed/error.c
index c881878e56d3..5313c5cb2b80 100644
--- a/arch/x86/boot/compressed/error.c
+++ b/arch/x86/boot/compressed/error.c
@@ -22,3 +22,22 @@ void error(char *m)
 	while (1)
 		asm("hlt");
 }
+
+/* EFI libstub  provides vsnprintf() */
+#ifdef CONFIG_EFI_STUB
+void panic(const char *fmt, ...)
+{
+	static char buf[1024];
+	va_list args;
+	int len;
+
+	va_start(args, fmt);
+	len = vsnprintf(buf, sizeof(buf), fmt, args);
+	va_end(args);
+
+	if (len && buf[len - 1] == '\n')
+		buf[len - 1] = '\0';
+
+	error(buf);
+}
+#endif
diff --git a/arch/x86/boot/compressed/error.h b/arch/x86/boot/compressed/error.h
index 1de5821184f1..86fe33b93715 100644
--- a/arch/x86/boot/compressed/error.h
+++ b/arch/x86/boot/compressed/error.h
@@ -6,5 +6,6 @@
 
 void warn(char *m);
 void error(char *m) __noreturn;
+void panic(const char *fmt, ...) __noreturn __cold;
 
 #endif /* BOOT_COMPRESSED_ERROR_H */
diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
index de858a5180b6..e6b92e822ddd 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 +14,39 @@
 
 extern struct boot_params *boot_params;
 
+/*
+ * accept_memory() and process_unaccepted_memory() called from EFI stub which
+ * runs before decompresser and its early_tdx_detect().
+ *
+ * Enumerate TDX directly from the early users.
+ */
+static bool early_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 (early_is_tdx_guest())
+		tdx_accept_memory(start, end);
+	else
+		error("Cannot accept memory: unknown platform\n");
 }
 
 /*
diff --git a/arch/x86/boot/compressed/tdx-shared.c b/arch/x86/boot/compressed/tdx-shared.c
new file mode 100644
index 000000000000..5ac43762fe13
--- /dev/null
+++ b/arch/x86/boot/compressed/tdx-shared.c
@@ -0,0 +1,2 @@
+#include "error.h"
+#include "../../coco/tdx/tdx-shared.c"
diff --git a/arch/x86/boot/compressed/tdx.c b/arch/x86/boot/compressed/tdx.c
index 918a7606f53c..de1d4a87418d 100644
--- a/arch/x86/boot/compressed/tdx.c
+++ b/arch/x86/boot/compressed/tdx.c
@@ -3,12 +3,17 @@
 #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>
+
+static u64 cc_mask;
 
 /* Called from __tdx_hypercall() for unrecoverable failure */
 void __tdx_hypercall_failed(void)
@@ -16,6 +21,38 @@ void __tdx_hypercall_failed(void)
 	error("TDVMCALL failed. TDX module bug?");
 }
 
+static u64 get_cc_mask(void)
+{
+	struct tdx_module_output out;
+	unsigned int gpa_width;
+
+	/*
+	 * TDINFO TDX module call is used to get the TD execution environment
+	 * information like GPA width, number of available vcpus, debug mode
+	 * information, etc. More details about the ABI can be found in TDX
+	 * Guest-Host-Communication Interface (GHCI), section 2.4.2 TDCALL
+	 * [TDG.VP.INFO].
+	 *
+	 * The GPA width that comes out of this call is critical. TDX guests
+	 * can not meaningfully run without it.
+	 */
+	if (__tdx_module_call(TDX_GET_INFO, 0, 0, 0, 0, &out))
+		error("TDCALL GET_INFO failed (Buggy TDX module!)\n");
+
+	gpa_width = out.rcx & GENMASK(5, 0);
+
+	/*
+	 * The highest bit of a guest physical address is the "sharing" bit.
+	 * Set it for shared pages and clear it for private pages.
+	 */
+	return BIT_ULL(gpa_width - 1);
+}
+
+u64 cc_mkdec(u64 val)
+{
+	return val & ~cc_mask;
+}
+
 static inline unsigned int tdx_io_in(int size, u16 port)
 {
 	struct tdx_hypercall_args args = {
@@ -70,6 +107,8 @@ void early_tdx_detect(void)
 	if (memcmp(TDX_IDENT, sig, sizeof(sig)))
 		return;
 
+	cc_mask = get_cc_mask();
+
 	/* Use hypercalls instead of I/O instructions */
 	pio_ops.f_inb  = tdx_inb;
 	pio_ops.f_outb = tdx_outb;
diff --git a/arch/x86/coco/tdx/Makefile b/arch/x86/coco/tdx/Makefile
index 46c55998557d..2c7dcbf1458b 100644
--- a/arch/x86/coco/tdx/Makefile
+++ b/arch/x86/coco/tdx/Makefile
@@ -1,3 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0
 
-obj-y += tdx.o tdcall.o
+obj-y += tdx.o tdx-shared.o tdcall.o
diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
new file mode 100644
index 000000000000..ee74f7bbe806
--- /dev/null
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -0,0 +1,95 @@
+#include <asm/tdx.h>
+#include <asm/pgtable.h>
+
+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 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 (pg_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;
+}
+
+bool tdx_enc_status_changed_phys(phys_addr_t start, phys_addr_t end, bool enc)
+{
+	if (!enc) {
+		/* Set the shared (decrypted) bits: */
+		start |= cc_mkdec(0);
+		end   |= cc_mkdec(0);
+	}
+
+	/*
+	 * 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))
+		return false;
+
+	/* private->shared conversion  requires only MapGPA call */
+	if (!enc)
+		return true;
+
+	/*
+	 * 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)
+			return false;
+		start += accept_size;
+	}
+
+	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);
+}
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 9e6557d7514c..1392ebc3b406 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -713,46 +713,6 @@ static bool tdx_cache_flush_required(void)
 	return true;
 }
 
-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 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 (pg_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;
-}
-
 /*
  * 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
@@ -761,51 +721,9 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
 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);
-
-	if (!enc) {
-		/* Set the shared (decrypted) bits: */
-		start |= cc_mkdec(0);
-		end   |= cc_mkdec(0);
-	}
-
-	/*
-	 * 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))
-		return false;
-
-	/* private->shared conversion  requires only MapGPA call */
-	if (!enc)
-		return true;
+	phys_addr_t end = __pa(vaddr + numpages * PAGE_SIZE);
 
-	/*
-	 * 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)
-			return false;
-		start += accept_size;
-	}
-
-	return true;
+	return tdx_enc_status_changed_phys(start, end, enc);
 }
 
 void __init tdx_early_init(void)
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 562b3f4cbde8..3afbba545a0d 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -92,5 +92,7 @@ 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/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 234197ec17e4..3a7340ad9a4b 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -50,6 +50,8 @@ bool tdx_early_handle_ve(struct pt_regs *regs);
 
 int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport);
 
+bool tdx_enc_status_changed_phys(phys_addr_t start, phys_addr_t end, bool enc);
+
 #else
 
 static inline void tdx_early_init(void) { };
diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
index a0a58486eb74..a521f8c0987d 100644
--- a/arch/x86/mm/unaccepted_memory.c
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -6,6 +6,7 @@
 
 #include <asm/io.h>
 #include <asm/setup.h>
+#include <asm/shared/tdx.h>
 #include <asm/unaccepted_memory.h>
 
 /* Protects unaccepted memory bitmap */
@@ -61,7 +62,13 @@ 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);
 	}
 	spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
-- 
2.39.2

Re: [PATCHv9 00/14] mm, x86/cc: Implement support for unaccepted memory

[Vlastimil Babka]

On 3/30/23 13:49, 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, 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.
> 
> -- Fragmentation study --
> 
> Vlastimil and Mel were concern about effect of unaccepted memory on
> fragmentation prevention measures in page allocator. I tried to evaluate
> it, but it is tricky. As suggested I tried to run multiple parallel kernel
> builds and follow how often kmem:mm_page_alloc_extfrag gets hit.
> 
> I don't like the results. Not because unaccepted memory is slow, but
> because the test is way too noisy to produce sensible information.

Hmm yeah it can be noisy. Did you try to only count events that have
fragmenting=1 and/or MIGRATE_MOVABLE as fallback_migratetype? As those are
the really bad events.

> So, I run 8 parallel builds of kernel, 16 jobs each in a VM with 16 CPU
> and 16G of RAM. I compared unpatched base-line (mm-unstable) with the tree
> that has patchset applied. For the later case, all memory above 1G was
> considered unaccepted with fake_unaccepted_start=1G. Around 14G of RAM was
> accounted as unaccepted after the boot. The test got all memory accepted.
> 
> 		kmem:mm_page_alloc_extfrag		Time elapsed
> Base line:
> Run 1		837					1803.21s
> Run 2		3,845					1785.87s
> Run 3		1,704					1883.59s
> 
> Patched:
> Run 1		905					1876.02s
> Run 2		845					1758.50s
> Run 3		1276					1876.13s
> 
> As you can see the numbers are all over the place.
> 
> The good news is that unaccepted memory doesn't make picture notably worse.

Yeah that at least somehow confirms no big surprises. I wouldn't expect any
with the v9 design of watermarks handling.

> I am open to suggestions on how to test it better.
> 
> Also, feel free to play with it yourself. fake_unaccepted_start= doesn't
> require any special setup.
> 
> --
> 
> The tree can be found here:
> 
> https://github.com/intel/tdx.git guest-unaccepted-memory
> 
> The patchset depends on MAX_ORDER changes in MM tree.
> 
> v9:
>  - Accept memory up to high watermark when kernel runs out of free memory;
>  - Treat unaccepted memory as unusable in __zone_watermark_unusable_free();
>  - Per-zone unaccepted memory accounting;
>  - All pages on unaccepted list are MAX_ORDER now;
>  - accept_memory=eager in cmdline to pre-accept memory during the boot;
>  - Implement fake unaccepted memory;
>  - Sysfs handle to accept memory manually;
>  - Drop PageUnaccepted();
>  - Rename unaccepted_pages static key to zones_with_unaccepted_pages;
> v8:
>  - Rewrite core-mm support for unaccepted memory (patch 02/14);
>  - s/UnacceptedPages/Unaccepted/ in meminfo;
>  - Drop arch/x86/boot/compressed/compiler.h;
>  - Fix build errors;
>  - Adjust commit messages and comments;
>  - Reviewed-bys from Dave and Borislav;
>  - Rebased to tip/master.
> v7:
>  - Rework meminfo counter to use PageUnaccepted() and move to generic code;
>  - Fix range_contains_unaccepted_memory() on machines without unaccepted memory;
>  - Add Reviewed-by from David;
> 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 (14):
>   x86/boot: Centralize __pa()/__va() definitions
>   mm: Add support for unaccepted memory
>   mm/page_alloc: Fake unaccepted memory
>   mm/page_alloc: Add sysfs handle to accept accept_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/tdx: Make _tdx_hypercall() and __tdx_module_call() available in
>     boot stub
>   x86/tdx: Refactor try_accept_one()
>   x86/tdx: Add unaccepted memory support
> 
>  Documentation/x86/zero-page.rst          |   1 +
>  arch/x86/Kconfig                         |   2 +
>  arch/x86/boot/bitops.h                   |  40 ++++
>  arch/x86/boot/compressed/Makefile        |   3 +-
>  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/efi.h           |   1 +
>  arch/x86/boot/compressed/error.c         |  19 ++
>  arch/x86/boot/compressed/error.h         |   1 +
>  arch/x86/boot/compressed/find.c          |  54 +++++
>  arch/x86/boot/compressed/find.h          |  79 ++++++++
>  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           | 122 +++++++++++
>  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-shared.c    |   2 +
>  arch/x86/boot/compressed/tdx.c           |  39 ++++
>  arch/x86/coco/tdx/Makefile               |   2 +-
>  arch/x86/coco/tdx/tdx-shared.c           |  95 +++++++++
>  arch/x86/coco/tdx/tdx.c                  | 118 +----------
>  arch/x86/include/asm/page.h              |   3 +
>  arch/x86/include/asm/shared/tdx.h        |  53 +++++
>  arch/x86/include/asm/tdx.h               |  21 +-
>  arch/x86/include/asm/unaccepted_memory.h |  16 ++
>  arch/x86/include/uapi/asm/bootparam.h    |   2 +-
>  arch/x86/kernel/e820.c                   |  17 ++
>  arch/x86/mm/Makefile                     |   2 +
>  arch/x86/mm/unaccepted_memory.c          | 107 ++++++++++
>  drivers/base/node.c                      |   7 +
>  drivers/firmware/efi/Kconfig             |  14 ++
>  drivers/firmware/efi/efi.c               |   1 +
>  drivers/firmware/efi/libstub/x86-stub.c  |  98 +++++++--
>  fs/proc/meminfo.c                        |   5 +
>  include/linux/efi.h                      |   3 +-
>  include/linux/mmzone.h                   |   8 +
>  mm/internal.h                            |  13 ++
>  mm/memblock.c                            |   9 +
>  mm/mm_init.c                             |   7 +
>  mm/page_alloc.c                          | 246 +++++++++++++++++++++++
>  mm/vmstat.c                              |   3 +
>  47 files changed, 1368 insertions(+), 176 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/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/boot/compressed/tdx-shared.c
>  create mode 100644 arch/x86/coco/tdx/tdx-shared.c
>  create mode 100644 arch/x86/include/asm/unaccepted_memory.h
>  create mode 100644 arch/x86/mm/unaccepted_memory.c
> 

Re: [PATCHv9 00/14] mm, x86/cc: Implement support for unaccepted memory

[Kirill A. Shutemov]

On Mon, Apr 03, 2023 at 04:42:54PM +0200, Vlastimil Babka wrote:
> Hmm yeah it can be noisy. Did you try to only count events that have
> fragmenting=1 and/or MIGRATE_MOVABLE as fallback_migratetype? As those are
> the really bad events.

I finally got around to retest it.

		total	fragmenting	movable	fragmenting&&movable
base-1:		957	583		353	0
base-2:		2715	2343		359	0
base-3:		2033	1669		353	0
patched-1:	1325	929		371	0
patched-2:	2844	2451		371	0
patched-3:	1304	917		361	0

fragmenting=1 is defined as fallback_order<pageblock_order which is most
of them.

Patched kernel showed slightly elevated movable(fallback_migratetype=1)
cases. Is it critical?

There's no allocations that is fragmenting and movable. Hm.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [PATCHv9 00/14] mm, x86/cc: Implement support for unaccepted memory

[Vlastimil Babka]

On 4/16/23 21:19, Kirill A. Shutemov wrote:
> On Mon, Apr 03, 2023 at 04:42:54PM +0200, Vlastimil Babka wrote:
>> Hmm yeah it can be noisy. Did you try to only count events that have
>> fragmenting=1 and/or MIGRATE_MOVABLE as fallback_migratetype? As those are
>> the really bad events.
> 
> I finally got around to retest it.
> 
> 		total	fragmenting	movable	fragmenting&&movable
> base-1:		957	583		353	0
> base-2:		2715	2343		359	0
> base-3:		2033	1669		353	0
> patched-1:	1325	929		371	0
> patched-2:	2844	2451		371	0
> patched-3:	1304	917		361	0
> 
> fragmenting=1 is defined as fallback_order<pageblock_order which is most
> of them.
> 
> Patched kernel showed slightly elevated movable(fallback_migratetype=1)
> cases. Is it critical?

Maybe it's still not statistically significant anyway, also not as cricical
as fragmenting&movable.

> There's no allocations that is fragmenting and movable. Hm.

It probably means your test wasn't stressfull enough to inflict a mix of
rapid movable an unmovable allocations when memory is nearly full. But at
that point the memory is all accepted, so we don't need such scenario. The
important thing is that this kind of events didn't start happening during
the gradual memory accepting phase.