On Fri, Jul 23, 2021 at 06:23:39PM +0300, Mike Rapoport wrote:

quoted

@@ -1318,9 +1327,14 @@ void __init e820__memblock_setup(void)
 		if (entry->type == E820_TYPE_SOFT_RESERVED)
 			memblock_reserve(entry->addr, entry->size);
 
-		if (entry->type != E820_TYPE_RAM && entry->type != E820_TYPE_RESERVED_KERN)
+		if (entry->type != E820_TYPE_RAM &&
+		    entry->type != E820_TYPE_RESERVED_KERN &&
+		    entry->type != E820_TYPE_UNACCEPTED)
 			continue;

If I understand correctly, you assume that

* E820_TYPE_RAM and E820_TYPE_RESERVED_KERN regions are already accepted by
  firmware/booloader
* E820_TYPE_UNACCEPTED would have been E820_SYSTEM_RAM if we'd disabled
  encryption

What happens with other types? Particularly E820_TYPE_ACPI and
E820_TYPE_NVS that may reside in memory and might have been accepted by
BIOS.

Any accessible memory that not marked as UNACCEPTED has to be accepted
before kernel gets control.

quoted

 
+		if (entry->type == E820_TYPE_UNACCEPTED)
+			mark_unaccepted(entry->addr, end);
+
 		memblock_add(entry->addr, entry->size);
 	}
 

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 72920af0b3c0..db9d1bcac9ed 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c

@@ -944,6 +944,8 @@ void __init setup_arch(char **cmdline_p)
 	if (movable_node_is_enabled())
 		memblock_set_bottom_up(true);
 #endif
+	/* TODO: make conditional */
+	memblock_set_bottom_up(true);

  
If memory is accepted during memblock allocations this should not really
matter.
Bottom up would be preferable if we'd like to reuse as much of already
accepted memory as possible before page allocator is up.

One of the main reason for this feature is to speed up boot time and
re-usinging preaccepted memory fits the goal.

quoted

--- a/mm/memblock.c
+++ b/mm/memblock.c

@@ -814,6 +814,7 @@ int __init_memblock memblock_reserve(phys_addr_t base, phys_addr_t size)
 	memblock_dbg("%s: [%pa-%pa] %pS\n", __func__,
 		     &base, &end, (void *)_RET_IP_);
 
+	accept_pages(base, base + size);

Hmm, I'm not sure memblock_reserve() is the right place to accept pages. It
can be called to reserve memory owned by firmware which not necessarily
would be encrypted. Besides, memblock_reserve() may be called for absent
memory, could be it'll confuse TDX/SEV?

Such memory will not be marked as unaccepted and accept_pages() will do
nothing.

Ideally, the call to accept_pages() should live in
memblock_alloc_range_nid(), but unfortunately there still stale
memblock_find_in_range() + memblock_reserve() pairs in x86 setup code.

memblock_reserve() is the root of memory allocation in the early boot and
it is natual place to do the trick. Unless we have a good reason to move
it somewhere I would keep it here.

-- 
 Kirill A. Shutemov