diff mbox series

[v9,5/8] efi_loader: remove memory occupied by a ramdisk from EFI memory map

Message ID 20250317083402.412310-6-sughosh.ganu@linaro.org
State New
Headers show
Series Add pmem node for preserving distro ISO's | expand

Commit Message

Sughosh Ganu March 17, 2025, 8:33 a.m. UTC 
From: Ilias Apalodimas <ilias.apalodimas@linaro.org>

ACPI has NFIT and NVDIMM support to provide ramdisks to the OS. Linux
and device trees have support for persistent memory(pmem) devices. The
firmware can then add a pmem node for the region of memory occupied by
the ramdisk when passing the device-tree to the OS.

It's worth noting that for linux to instantiate the /dev/pmemX device,
the memory described in the pmem node has to be omitted from the EFI
memory map we hand over to the OS if ZONE_DEVICES and SPARSEMEM is
enabled. With those enabled the pmem driver ends up calling
devm_memremap_pages() instead of devm_memremap(). The latter works
whether the memory is omitted or marked as reserved, but mapping pages
only works if the memory is omitted.

On top of that, depending on how the kernel is configured, that memory
area must be page aligned or 2MiB aligned. PowerPC is an exception here
and requires 16MiB alignment, but since we don't have EFI support for
it, limit the alignment to 2MiB.

Ensure that the ISO image is 2MiB aligned and remove the region
occupied by the image from the EFI memory map.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
---
* Re-word the commit message to indicate that the ramdisk region is
  being removed from the EFI memory map
* Fix the comment in prepare_loaded_image() on similar lines as above
* s/pmem memory area/pmem memory areas/
* s/MB/MiB/g

 lib/efi_loader/efi_bootmgr.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/lib/efi_loader/efi_bootmgr.c b/lib/efi_loader/efi_bootmgr.c
index c6124c590d9..f9534ef85ed 100644
--- a/lib/efi_loader/efi_bootmgr.c
+++ b/lib/efi_loader/efi_bootmgr.c
@@ -18,6 +18,8 @@ 
 #include <efi_loader.h>
 #include <efi_variable.h>
 #include <asm/unaligned.h>
+#include <linux/kernel.h>
+#include <linux/sizes.h>
 
 static const struct efi_boot_services *bs;
 static const struct efi_runtime_services *rs;
@@ -348,6 +350,7 @@  static efi_status_t prepare_loaded_image(u16 *label, ulong addr, ulong size,
 					 struct efi_device_path **dp,
 					 struct udevice **blk)
 {
+	u64 pages;
 	efi_status_t ret;
 	struct udevice *ramdisk_blk;
 
@@ -362,13 +365,18 @@  static efi_status_t prepare_loaded_image(u16 *label, ulong addr, ulong size,
 	}
 
 	/*
-	 * TODO: expose the ramdisk to OS.
-	 * Need to pass the ramdisk information by the architecture-specific
-	 * methods such as 'pmem' device-tree node.
+	 * Linux supports 'pmem' which allows OS installers to find, reclaim
+	 * the mounted images and continue the installation since the contents
+	 * of the pmem region are treated as local media.
+	 *
+	 * The memory regions used for it needs to be carved out of the EFI
+	 * memory map.
 	 */
-	ret = efi_add_memory_map(addr, size, EFI_RESERVED_MEMORY_TYPE);
+	pages = efi_size_in_pages(size + (addr & EFI_PAGE_MASK));
+	ret = efi_update_memory_map(addr, pages, EFI_CONVENTIONAL_MEMORY,
+				    false, true);
 	if (ret != EFI_SUCCESS) {
-		log_err("Memory reservation failed\n");
+		log_err("Failed to reserve memory\n");
 		goto err;
 	}
 
@@ -490,6 +498,13 @@  static efi_status_t try_load_from_uri_path(struct efi_device_path_uri *uridp,
 		ret = EFI_INVALID_PARAMETER;
 		goto err;
 	}
+	/*
+	 * Depending on the kernel configuration, pmem memory areas must be
+	 * page aligned or 2MiB aligned. PowerPC is an exception here and
+	 * requires 16MiB alignment, but since we don't have EFI support for
+	 * it, limit the alignment to 2MiB.
+	 */
+	image_size = ALIGN(image_size, SZ_2M);
 
 	/*
 	 * If the file extension is ".iso" or ".img", mount it and try to load