linux-kernel - [PATCH 2/2] efi: Don't add memblocks for unusable memory

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Date: Fri,  2 Feb 2024 08:34:33 -0800
From: Andrew Bresticker <abrestic@...osinc.com>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	Andrew Bresticker <abrestic@...osinc.com>
Subject: [PATCH 2/2] efi: Don't add memblocks for unusable memory

Adding memblocks (even if nomap) for such regions unnecessarily consumes
resources by creating struct pages for memory that may never be used or,
in the case of soft-reserved regions, prevents the memory from later
being hotplugged in by dax_kmem. This is also consistent with how x86
handles unusable memory found in the EFI memory map.

Signed-off-by: Andrew Bresticker <abrestic@...osinc.com>
---
 drivers/firmware/efi/efi-init.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/drivers/firmware/efi/efi-init.c b/drivers/firmware/efi/efi-init.c
index d4987d013080..f05bacac89b7 100644
--- a/drivers/firmware/efi/efi-init.c
+++ b/drivers/firmware/efi/efi-init.c
@@ -24,13 +24,6 @@
 
 unsigned long __initdata screen_info_table = EFI_INVALID_TABLE_ADDR;
 
-static int __init is_memory(efi_memory_desc_t *md)
-{
-	if (md->attribute & (EFI_MEMORY_WB|EFI_MEMORY_WT|EFI_MEMORY_WC))
-		return 1;
-	return 0;
-}
-
 /*
  * Translate a EFI virtual address into a physical address: this is necessary,
  * as some data members of the EFI system table are virtually remapped after
@@ -195,12 +188,9 @@ static __init void reserve_regions(void)
 		memrange_efi_to_native(&paddr, &npages);
 		size = npages << PAGE_SHIFT;
 
-		if (is_memory(md)) {
+		if (is_usable_memory(md)) {
 			early_init_dt_add_memory_arch(paddr, size);
 
-			if (!is_usable_memory(md))
-				memblock_mark_nomap(paddr, size);
-
 			/* keep ACPI reclaim memory intact for kexec etc. */
 			if (md->type == EFI_ACPI_RECLAIM_MEMORY)
 				memblock_reserve(paddr, size);
-- 
2.34.1