[PATCH v3 07/17] x86/efi: Drop EFI_MEMORY_RUNTIME check from __ioremap_check_other()

Ard Biesheuvel
2026-04-23T15:21:09Z

__ioremap_check_other() is called when memremap() is used on memory that
turns out to be reserved. This may be the case for ESRT or MOK tables
that are reserved via efi_mem_reserve(), in which case they will be
covered by EfiBootServicesData entries in the EFI memory map.

Such entries are created with the EFI_MEMORY_RUNTIME attribute set, to
distinguish them from EfiBootServicesData entries that were reserved
only temporarily, in order to work around firmware bugs.

However, given that
a) __ioremap_check_other() is only called for memory that could not be
mapped using try_ram_remap(),
b) on x86, the EFI memory map only retains EfiBootServicesData entries that
cover a permanent reservation,
the EFI_MEMORY_RUNTIME check is redundant, and can be dropped.

This removes the need to set this attribute in the first place, which is
desirable as it results in considerable complexity in managing the EFI
memory map on x86. This will be addressed in follow-up work.

While at it, use switch() rather than if() to avoid multiple calls to
efi_mem_type(), which is backed by a hypervisor call in some cases.

Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/mm/ioremap.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 12c8180ca1ba..50377423d422 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -124,10 +124,12 @@ static void __ioremap_check_other(resource_size_t addr, struct ioremap_desc *des
if (!IS_ENABLED(CONFIG_EFI))
return;

- if (efi_mem_type(addr) == EFI_RUNTIME_SERVICES_DATA ||
- (efi_mem_type(addr) == EFI_BOOT_SERVICES_DATA &&
- efi_mem_attributes(addr) & EFI_MEMORY_RUNTIME))
+ switch (efi_mem_type(addr)) {
+ case EFI_RUNTIME_SERVICES_DATA:
+ case EFI_BOOT_SERVICES_DATA:
desc->flags |= IORES_MAP_ENCRYPTED;
+ break;
+ }
}

static int __ioremap_collect_map_flags(struct resource *res, void *arg)