[PATCH v4 5/5] blkmap: add pmem nodes for blkmap memory mapped slices

[Ilias Apalodimas]

Hi Sughosh

This generally looks ok, but I don't love the idea of unconditionally
preserving all slices regardless of their usage.
Basically, if a user doesn't unmap that slice it will end in kernel
memory. My fear is that someone will forget device sensitive data in a
blkmap....

On Mon, 3 Feb 2025 at 12:59, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
>
> The EFI HTTP boot puts the ISO installer image at some location in
> memory which needs to be added to the devicetree as persistent
> memory (pmem) node. The OS installer then gets information about the
> presence of this ISO image through the pmem node and proceeds with the
> installation.
>
> In U-Boot, this ISO image gets mounted as a blkmap device, with a
> memory mapped slice. Add a helper function which iterates through all
> such memory mapped blkmap slices, and calls the FDT fixup function to
> add the pmem node. Invoke this helper function as part of the DT fixup
> which happens before booting the OS.
>
> Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> ---
> Changes since V3:
> * Move the definition of the helper function to the efi_helper.c
> * Remove the region of the blkmap mem map device from the EFI memory
>   map along with adding the pmem node
>

[...]

> @@ -680,3 +683,52 @@ out:
>
>         return ret;
>  }
> +
> +static int add_blkmap_pmem_nodes(void *fdt, struct blkmap *bm)
> +{
> +       int ret;
> +       u32 size;
> +       ulong addr;
> +       efi_status_t status;
> +       struct blkmap_mem *bmm;
> +       struct blkmap_slice *bms;
> +       struct blk_desc *bd = dev_get_uclass_plat(bm->blk);
> +
> +       list_for_each_entry(bms, &bm->slices, node) {
> +               if (bms->type != BLKMAP_SLICE_MEM)
> +                       continue;

Can we convert the 'type' to 'preserve' and teach
blkmap_create_ramdisk() to pass that flag?
This way we can unconditionally pass it from EFI HTTP installers, and
let the command line users decide if they want to preserve it.


> +
> +               bmm = container_of(bms, struct blkmap_mem, slice);
> +
> +               addr = (ulong)(uintptr_t)bmm->addr;
> +               size = (u32)bms->blkcnt << bd->log2blksz;
> +
> +               ret = fdt_fixup_pmem_region(fdt, addr, size);
> +               if (ret)
> +                       return ret;
> +
> +               status = efi_remove_memory_map(addr, size,
> +                                              EFI_CONVENTIONAL_MEMORY);
> +               if (status != EFI_SUCCESS)
> +                       return -1;
> +       }
> +
> +       return 0;
> +}
> +


Thanks
/Ilias