On 11/8/21 10:40 AM, Martin Fernandez wrote:
> On 11/5/21, Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
>> On 11/5/21 2:27 PM, Martin Fernandez wrote:
>>> +void __init e820__mark_regions_as_crypto_capable(u64 start, u64 size)
>>> +{
>>> + int i;
>>> + u64 end = start + size;
>>> +
>>> + for (i = 0; i < e820_table->nr_entries; i++) {
>>> + struct e820_entry *const entry = &e820_table->entries[i];
>>> +
>>> + if (entry->addr >= start && entry->addr + entry->size <= end)
>>> + entry->crypto_capable = true;
>>> + }
>>> +}
>>
>> Looking at this in isolation, this is really tricky. I have no idea
>> what this is _supposed_ to or expected to be doing. It also makes me
>> wonder what happens when start/size don't line up exactly on an e820 entry.
>
> Do you think it's better to just add new entries, just as they are in
> the EFI memmap and then let e820__update_table handle them?
>
> Although, as it is it's faster, the other way would be clearer in the
> code (since efi_mark_e820_regions_as_crypto_capable in part 4/5 isn't
> also the nicest of the functions and with this change it would be very
> straightforward), but it would require one e820__update_table. Also,
> it would more accurate, since if you call this with a start and size
> that doesn't cover at least one e820_entry then it will do nothing.
I was actually trying to make a comment about this function's lack of
documentation.
But, you make a good point about the alternate approach. I don't have a
preference either way.
>>> @@ -327,6 +343,8 @@ int __init e820__update_table(struct e820_table
>>> *table)
>>> unsigned long long last_addr;
>>> u32 new_nr_entries, overlap_entries;
>>> u32 i, chg_idx, chg_nr;
>>> + bool current_crypto;
>>> + bool last_crypto = false;
>>>
>>> /* If there's only one memory region, don't bother: */
>>> if (table->nr_entries < 2)
>>> @@ -388,13 +406,17 @@ int __init e820__update_table(struct e820_table
>>> *table)
>>> * 1=usable, 2,3,4,4+=unusable)
>>> */
>>> current_type = 0;
>>> + current_crypto = false;
>>> for (i = 0; i < overlap_entries; i++) {
>>> + current_crypto = current_crypto || overlap_list[i]->crypto_capable;
>>
>> No comment, eh?
>>
>> This seems backwards to me. If there are overlapping region and only
>> one is crypto-capable, shouldn't the whole thing become non-crypto-capable?
>
> The reason for that is that right now, if a region is mark as
> crypto_capable is because EFI memmap says so, and again, right now
> that's the only source to fill the crypto_capable value, so I have to
> "believe" it. Now that I think about it, yes I should have a least put
> a comment on it.
My concern was if:
current_crypto=0
and
overlap_list[i]->crypto_capable=1
Doesn't that mean a non-crypto entry is being parsed, but current_crypto
will end up as 1?
>>> /* Continue building up new map based on this information: */
>>> - if (current_type != last_type || e820_nomerge(current_type)) {
>>> + if (current_type != last_type ||
>>> + current_crypto != last_crypto ||
>>> + e820_nomerge(current_type)) {
>>> if (last_type != 0) {
>>> new_entries[new_nr_entries].size = change_point[chg_idx]->addr -
>>> last_addr;
>>> /* Move forward only if the new size was non-zero: */
>>> @@ -406,6 +428,9 @@ int __init e820__update_table(struct e820_table
>>> *table)
>>> if (current_type != 0) {
>>> new_entries[new_nr_entries].addr = change_point[chg_idx]->addr;
>>> new_entries[new_nr_entries].type = current_type;
>>> + new_entries[new_nr_entries].crypto_capable = current_crypto;
>>> +
>>> + last_crypto = current_crypto;
>>> last_addr = change_point[chg_idx]->addr;
>>> }
>>> last_type = current_type;
>>
>> The "current_crypto != last_crypto" checks seem to go with the
>> current_type/last_type checks. I'm naively surprised that the
>> last_crypto assignment wasn't paired with the last_type assignment.
>>
>> I kinda get the impression this was just quickly hacked in here. It
>> seems like "crypto" and "type" are very closely related in how they are
>> being handled. It's a shame they're not being managed in a common way.
>
> Yes, "crypto" and "type" seems really close, but to be honest, this
> function has a very weird flow, or something that I couldn't
> completely understand. After a while thinking about it I came up with
> that.
>
> Again, this function is a pain, but I'll dedicate it some more time to
> see if I can come up with something better.
Please do. Like you said, there's probably more context that it would
be helpful to understand.
