Merge tag 'efi-next-26032025' of https://source.denx.de/u-boot/custodians/u-boot-tpm into next

When trying to boot an OS installer or a live image via EFI HTTP the
following happens
- U-Boot downloads the image and mounts it in memory
- The EFI subsystem is invoked and the image is started
- The OS calls ExitBootServices and the memory that holds the mounted
  image might get overwritten

This results in installers complaining that they can't find installer
medium or live images complaining they can't find the root filesystem.

ACPI already deals with it by having NFIT and NVDIMM to provide ramdisks
that need to be preserved by the OS. Linux and device trees have support
for persistent memory devices (pmem).

We can use them and inject a pmem node in the DT to preserve memory across the
entire boot sequence. Linux will just create a block device over the reserved
memory and installers/images can re-discover it.

This is what it looks like from the OS perspective:

nd_pmem namespace0.0: unable to guarantee persistence of writes
pmem0: p1 p2 p3
EXT4-fs (pmem0p3): mounted filesystem f40f64a4-5b41-4828-856e-caaae2c1c2a0 r/w with ordered data mode. Quota mode: disabled.
EXT4-fs (pmem0p3): re-mounted f40f64a4-5b41-4828-856e-caaae2c1c2a0 r/w. Quota mode: disabled.
Adding 45052k swap on /dev/pmem0p2.  Priority:-2 extents:1 across:45052k SS
root@genericarm64:~# mount | grep pmem
/dev/pmem0p3 on / type ext4 (rw,relatime)
/dev/pmem0p1 on /boot type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)

It's worth noting that Linux behaves differently with reserved memory
(at least on arm64) and that depends on kernel config options.
CONFIG_ZONE_DEVICES and CONFIG_ARM64_PMEM are such options. It boils down to
how the kernel tries to map pages. If devm_memremap_pages() gets called instead
of devm_memremap() mapping the memory fails.

The only safe way is to remove the memory from the EFI memory map,
rather than defining it as /reserved no-map;/ in the DT.

4 files changed, 74 insertions, 1 deletions

diff --git a/include/blkmap.h b/include/blkmap.h
index d53095437fa..57555fda4fb 100644
--- a/include/blkmap.h
+++ b/include/blkmap.h
@@ -7,6 +7,7 @@
 #ifndef _BLKMAP_H
 #define _BLKMAP_H
 
+#include <blk.h>
 #include <dm/lists.h>
 
 /**
@@ -60,10 +61,12 @@ int blkmap_map_mem(struct udevice *dev, lbaint_t blknr, lbaint_t blkcnt,
  * @blknr: Start block number of the mapping
  * @blkcnt: Number of blocks to map
  * @paddr: The target physical memory address of the mapping
+ * @preserve: Mapping intended to be preserved for subsequent stages,
+ *		like the OS (e.g. ISO installer)
  * Returns: 0 on success, negative error code on failure
  */
 int blkmap_map_pmem(struct udevice *dev, lbaint_t blknr, lbaint_t blkcnt,
-		    phys_addr_t paddr);
+		    phys_addr_t paddr, bool preserve);
 
 /**
  * blkmap_from_label() - Find blkmap from label
@@ -102,4 +105,32 @@ int blkmap_destroy(struct udevice *dev);
 int blkmap_create_ramdisk(const char *label, ulong image_addr, ulong image_size,
 			  struct udevice **devp);
 
+/**
+ * blkmap_get_preserved_pmem_slices() - Look for memory mapped preserved slices
+ * @cb: Callback function to call for the blkmap slice
+ * @ctx: Argument to be passed to the callback function
+ *
+ * The function is used to iterate through all the blkmap slices, looking
+ * specifically for memory mapped blkmap mapping which has been
+ * created with the preserve attribute. The function looks for such slices
+ * with the relevant attributes and then calls the callback function which
+ * then does additional configuration as needed. The callback function is
+ * invoked for all the discovered slices, unless there is an error returned
+ * by the callback, in which case the function returns that error.
+ *
+ * The callback function has the following arguments
+ * @ctx:	Argument to be passed to the callback function
+ * @addr:	Start address of the memory mapped slice
+ * @size:	Size of the memory mapped slice
+ *
+ * Typically, the callback will perform some configuration needed for the
+ * information passed on to it. An example of this would be setting up the
+ * pmem node in a device-tree(passed through the ctx argument) with the
+ * parameters passed on to the callback.
+ *
+ * Return: 0 on success, negative error on failure
+ */
+int blkmap_get_preserved_pmem_slices(int (*cb)(void *ctx, u64 addr,
+					       u64 size), void *ctx);
+
 #endif	/* _BLKMAP_H */
diff --git a/include/efi.h b/include/efi.h
index d005cb6181e..f9bbb175c3a 100644
--- a/include/efi.h
+++ b/include/efi.h
@@ -705,4 +705,17 @@ static inline bool efi_use_host_arch(void)
  */
 int efi_get_pxe_arch(void);
 
+/**
+ * fdt_efi_pmem_setup() - Pmem setup in DT and EFI memory map
+ * @fdt: Devicetree to add the pmem nodes to
+ *
+ * Iterate through all the blkmap devices, look for BLKMAP_MEM devices,
+ * and add pmem nodes corresponding to the blkmap slice to the
+ * devicetree along with removing the corresponding region from the
+ * EFI memory map.
+ *
+ * Returns: 0 on success, negative error on failure
+ */
+int fdt_efi_pmem_setup(void *fdt);
+
 #endif /* _LINUX_EFI_H */
diff --git a/include/efi_loader.h b/include/efi_loader.h
index e9c10819ba2..5f769786786 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -878,6 +878,21 @@ efi_status_t efi_get_memory_map(efi_uintn_t *memory_map_size,
 /* Adds a range into the EFI memory map */
 efi_status_t efi_add_memory_map(u64 start, u64 size, int memory_type);
 
+/**
+ * efi_update_memory_map() - update the memory map by adding/removing pages
+ *
+ * @start:			start address, must be a multiple of
+ *				EFI_PAGE_SIZE
+ * @pages:			number of pages to add
+ * @memory_type:		type of memory added
+ * @overlap_conventional:	region may only overlap free(conventional)
+ *				memory
+ * @remove:			remove memory map
+ * Return:			status code
+ */
+efi_status_t efi_update_memory_map(u64 start, u64 pages, int memory_type,
+				   bool overlap_conventional, bool remove);
+
 /* Called by board init to initialize the EFI drivers */
 efi_status_t efi_driver_init(void);
 /* Called when a block device is added */
diff --git a/include/fdt_support.h b/include/fdt_support.h
index f0ad2e6b365..049190cf3d7 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -471,6 +471,20 @@ int fdt_valid(struct fdt_header **blobp);
  */
 int fdt_get_cells_len(const void *blob, char *nr_cells_name);
 
+/**
+ * fdt_fixup_pmem_region() - add a pmem node on the device tree
+ *
+ * This functions adds/updates a pmem node to the device tree.
+ * Usually used with EFI installers to preserve installer
+ * images
+ *
+ * @fdt:	device tree provided by caller
+ * @addr:	start address of the pmem node
+ * @size:	size of the memory of the pmem node
+ * Return:	0 on success or < 0 on failure
+ */
+int fdt_fixup_pmem_region(void *fdt, u64 pmem_start, u64 pmem_size);
+
 #endif /* !USE_HOSTCC */
 
 #ifdef USE_HOSTCC