Re: [PATCH v13 09/13] x86/sgx: Enclave Page Cache (EPC) memory manager

From: Dave Hansen
Date: Tue Aug 28 2018 - 17:26:49 EST

On 08/28/2018 02:22 PM, Sean Christopherson wrote:
> On Tue, Aug 28, 2018 at 07:07:33AM -0700, Dave Hansen wrote:
>> On 08/28/2018 01:35 AM, Jarkko Sakkinen wrote:
>>> On Mon, Aug 27, 2018 at 02:15:34PM -0700, Dave Hansen wrote:
>>>> On 08/27/2018 11:53 AM, Jarkko Sakkinen wrote:
>>>>> +struct sgx_epc_page_ops {
>>>>> + bool (*get)(struct sgx_epc_page *epc_page);
>>>>> + void (*put)(struct sgx_epc_page *epc_page);
>>>>> + bool (*reclaim)(struct sgx_epc_page *epc_page);
>>>>> + void (*block)(struct sgx_epc_page *epc_page);
>>>>> + void (*write)(struct sgx_epc_page *epc_page);
>>>>> +};
>>>> Why do we need a fancy, slow (retpoline'd) set of function pointers when
>>>> we only have one user of these (the SGX driver)?
>>> KVM has its own implementation for these operations.
>> That belongs in the changelog.
>> Also, where is the implementation? How can we assess this code that was
>> built to create an abstraction without both of the users?
> I can provide an early preview of the KVM reclaim code, but honestly
> I think that would do more harm than good. The VMX architecture for
> EPC reclaim is complex, even for SGX standards. Opening that can of
> worms would likely derail this discussion. That being said, this
> abstraction isn't exactly what KVM will need, but it's pretty close
> and gives us something to build on.

Please remove the abstraction code. We don't introduce infrastructure
which no one will use.