linux-kernel - Re: [PATCH V3 19/30] x86/sgx: Free up EPC pages directly to support large page ranges

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Date:   Tue, 5 Apr 2022 10:25:15 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Reinette Chatre <reinette.chatre@...el.com>,
        Jarkko Sakkinen <jarkko@...nel.org>
Cc:     dave.hansen@...ux.intel.com, tglx@...utronix.de, bp@...en8.de,
        luto@...nel.org, mingo@...hat.com, linux-sgx@...r.kernel.org,
        x86@...nel.org, seanjc@...gle.com, kai.huang@...el.com,
        cathy.zhang@...el.com, cedric.xing@...el.com,
        haitao.huang@...el.com, mark.shanahan@...el.com, hpa@...or.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 19/30] x86/sgx: Free up EPC pages directly to support
 large page ranges

On 4/5/22 10:13, Reinette Chatre wrote:
>>> +void sgx_direct_reclaim(void)
>>> +{
>>> +	if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
>>> +		sgx_reclaim_pages();
>>> +}
>> Please, instead open code this to both locations - not enough redundancy
>> to be worth of new function. Causes only unnecessary cross-referencing
>> when maintaining. Otherwise, I agree with the idea.
>>
> hmmm, that means the heart of the reclaimer (sgx_reclaim_pages()) would be
> made available for direct use from everywhere in the driver. I will look into this.

I like the change.  It's not about reducing code redundancy, it's about
*describing* what the code does.  Each location could have:

	/* Enter direct SGX reclaim: */
	if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
		sgx_reclaim_pages();

Or, it could just be:

	sgx_direct_reclaim();

Which also provides a logical choke point to add comments, like:

/*
 * sgx_direct_reclaim() should be called in locations where SGX
 * memory resources might be low and might be needed in order
 * to make forward progress.
 */
void sgx_direct_reclaim(void)
{
	...