Re: [PATCH v3 2/2] x86/sgx: Resolve EREMOVE page vs EAUG page data race

[Dave Hansen]

On 6/3/24 11:42, Haitao Huang wrote:
>> Second, convince me that this _needs_ a new bit.  Why can't we just have
>> a bit that effectively means "return EBUSY if you see this bit when
>> handling a fault".
> 
> IIUC, reclaimer_writing_to_pcmd() also uses
> SGX_ENCL_PAGE_BEING_RECLAIMED to check if a page is about being
> reclaimed in order to prevent its VA slot fro being freed. So I think we
> do need separate bit for EREMOVE which does not write to VA slot?

I think the bits should be centered around what action the code needs to
take and not what is being done to the page.

Right now, SGX_ENCL_PAGE_BEING_RECLAIMED has two logical meanings:

 1. Don't load the page
 2. The page is in the backing store

But now folks are suggesting that a new bit is added which means "do #1,
but not #2".

Let's take a step back and look at what logical outcomes we want in the
code and then create the bits based on _that_.