On 11/5/21 2:27 PM, Martin Fernandez wrote:
> Iterate over the EFI memmap finding the contiguous regions that are
> able to do hardware encryption (ie, those who have the
> EFI_MEMORY_CPU_CRYPTO enabled) and mark those in the e820_table.
It would also be nice to remind the reader about the connection between
EFI memory maps and the e820.
...
> +/*
> + * This assumes that there'll be no overlaps in the memory map
> + * (otherwise we'd have a deeper problem going on). It also assumes
> + * that the system DRAM regions are already sorted; in EDK2 based UEFI
> + * firmware the entries covering system DRAM are usually sorted, with
> + * additional MMIO entries appearing unordered. This is because the
> + * UEFI memory map is constructed from the GCD memory map, which is
> + * seeded with the DRAM regions at boot, and allocations are created
> + * by splitting them up.
> + */
> +static void __init efi_mark_e820_regions_as_crypto_capable(void)
> +{
> + efi_memory_desc_t *md;
> + struct contiguous_region prev_region;
> +
> + cr_init(&prev_region);
A little theory of operation for this would be nice. What's collected
in here? What does this region mean? Is the *entire* region in here
crypto-capable system RAM?
> + for_each_efi_memory_desc(md) {
> + if (md->attribute & EFI_MEMORY_CPU_CRYPTO) {
> + struct contiguous_region cur_region;
> +
> + efi_md_to_cr(md, &cur_region);
FWIW, I think that helper obfuscates more than it helps. I say, just
open-code it.
> + if (!cr_merge_regions(&prev_region, &cur_region)) {
> + cr_mark_e820_as_crypto_capable(&prev_region);
> + prev_region = cur_region;
> + } /* else: Merge succeeded, don't mark yet */
That's really unusual CodingStyle. Could you try to move those to a
more normal place: below or above the if() entirely.
> + } else if (!cr_is_empty(&prev_region)) {
> + cr_mark_e820_as_crypto_capable(&prev_region);
> + cr_init(&prev_region);
> + } /* else: All previous regions are already marked */
There are much nicer ways to write this. For instance, I'd much prefer:
/* Bail on empty regions: */
if (cr_is_empty(&prev_region))
continue;
/* Mark the region: */
cr_mark_e820_as_crypto_capable(&prev_region);
cr_init(&prev_region);
That makes the flow much more understandable. In general, you want to
keep the "main" flow if your code at the lowest indent and the exception
handling as indented.
> + }
> +
> + /* Mark last region (if any) */
> + if (!cr_is_empty(&prev_region))
> + cr_mark_e820_as_crypto_capable(&prev_region);
> +}
> +
> void __init efi_init(void)
> {
> if (IS_ENABLED(CONFIG_X86_32) &&
> @@ -494,6 +601,8 @@ void __init efi_init(void)
> set_bit(EFI_RUNTIME_SERVICES, &efi.flags);
> efi_clean_memmap();
>
> + efi_mark_e820_regions_as_crypto_capable();
> +
> if (efi_enabled(EFI_DBG))
> efi_print_memmap();
> }
>
