BOOT_DIRECT_XIP_REVERT results in erasing image every time

[rtborg]

When using CONFIG_BOOT_DIRECT_XIP=y, mcuboot works normally. When selecting CONFIG_BOOT_DIRECT_XIP_REVERT=y, mcuboot erases the primary image after flashing it.

My requirement is to flash mcuboot only and flash application at a later stage in the product life.

Here's an overview of the steps I am taking:

Bootloader:

• Compile with CONFIG_BOOT_DIRECT_XIP_REVERT=y
• Erase all flash and then flash bootloader
• The MCU only has bootloader in flash and no application at this point. I've added USB host functionality and mcuboot can copy a binary from an USB memory drive

Application:

• Compile with CONFIG_MCUBOOT_BOOTLOADER_MODE_DIRECT_XIP_WITH_REVERT=y
• Transfer zephyr.signed.confirmed.bin to primary slot using USB memory drive

After transfer, mcuboot always erases the image:

[00:00:03.910,000] <inf> mcuboot: USB firmware update status: Success
[00:00:05.916,000] <inf> mcuboot: Primary   slot: version=1.0.2+1000
[00:00:05.923,000] <inf> mcuboot: Image 0 Secondary slot: Image not found
[00:00:05.930,000] <dbg> mcuboot: boot_select_or_erase: Erasing faulty image in the primary slot.
[00:00:05.965,000] <inf> mcuboot: No slot to load for image 0
[00:00:05.971,000] <err> mcuboot: Unable to find bootable image

The same thing happens when I copy the non-confirmed image to the primary slot.
When debugging, the value of active_swap_state after calling boot_read_swap_state in function boot_select_or_erase is:

p *active_swap_state
$1 = {magic = 0x3, swap_type = 0x1, copy_done = 0x3, image_ok = 0x3, image_num = 0x0}

This causes the check of the magic number to fail.

My application flash map in the overlay file is:

        partitions {
            compatible = "fixed-partitions";
            #address-cells = <1>;
            #size-cells = <1>;

            boot_partition: partition@0 {
                label = "mcuboot";
                reg = <0x00000000 DT_SIZE_K(128)>;
            };
            /* The MCUBoot swap-move algorithm uses the last 3 sectors
             * of the primary slot0 for swap status and move.
             */
            slot0_partition: partition@20000 {
                label = "image-0";
                reg = <0x00020000 (DT_SIZE_M(3) + DT_SIZE_K(3 * 4))>; 
            };
            slot1_partition: partition@323000 {
                label = "image-1";
                reg = <0x00323000 DT_SIZE_M(3)>;
            };
            storage_partition: partition@623000 {
                label = "storage";
                reg = <0x00623000 (DT_SIZE_M(2) - DT_SIZE_K(140))>;
            };
        };

However, the size of zephyr.signed.confirmed.bin is 0x300000 bytes.

Am I misunderstanding the use of XIP_REVERT?