Re: [RFC PATCH v4 22/36] i386/tdx: Track RAM entries for TDX VM

[Gerd Hoffmann]

> +static int tdx_accept_ram_range(uint64_t address, uint64_t length)
> +{
> +    TdxRamEntry *e;
> +    int i;
> +
> +    for (i = 0; i < tdx_guest->nr_ram_entries; i++) {
> +        e = &tdx_guest->ram_entries[i];
> +
> +        if (address + length < e->address ||
> +            e->address + e->length < address) {
> +                continue;
> +        }
> +
> +        if (e->address > address ||
> +            e->address + e->length < address + length) {
> +            return -EINVAL;
> +        }

if (e->type == TDX_RAM_ADDED)
        return -EINVAL

> +        if (e->address == address && e->length == length) {
> +            e->type = TDX_RAM_ADDED;
> +        } else if (e->address == address) {
> +            e->address += length;
> +            e->length -= length;
> +            tdx_add_ram_entry(address, length, TDX_RAM_ADDED);
> +        } else if (e->address + e->length == address + length) {
> +            e->length -= length;
> +            tdx_add_ram_entry(address, length, TDX_RAM_ADDED);
> +        } else {
> +            TdxRamEntry tmp = {
> +                .address = e->address,
> +                .length = e->length,
> +            };
> +            e->length = address - tmp.address;
> +
> +            tdx_add_ram_entry(address, length, TDX_RAM_ADDED);
> +            tdx_add_ram_entry(address + length,
> +                              tmp.address + tmp.length - (address + length),
> +                              TDX_RAM_UNACCEPTED);
> +        }

I think all this can be simplified, by
  (1) Change the existing entry to cover the accepted ram range.
  (2) If there is room before the accepted ram range add a
      TDX_RAM_UNACCEPTED entry for that.
  (3) If there is room after the accepted ram range add a
      TDX_RAM_UNACCEPTED entry for that.

take care,
  Gerd