linux-kernel - Re: [PATCH v3 2/5] x86/sgx: Use sgx_free_epc_page() in sgx_reclaim

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Date:   Wed, 10 Mar 2021 07:55:35 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     linux-sgx@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/5] x86/sgx: Use sgx_free_epc_page() in
 sgx_reclaim_pages()

On 3/10/21 7:11 AM, Jarkko Sakkinen wrote:
>>> -		section = &sgx_epc_sections[epc_page->section];
>>> -		spin_lock(&section->lock);
>>> -		list_add_tail(&epc_page->list, &section->page_list);
>>> -		section->free_cnt++;
>>> -		spin_unlock(&section->lock);
>>> +		sgx_free_epc_page(epc_page);
>>>  	}
>>>  }
>> In current upstream (3fb6d0e00e), sgx_free_epc_page() calls __eremove().
>>  This code does not call __eremove().  That seems to be changing
>> behavior where none was intended.
> EREMOVE does not matter here, as it doesn't in almost all most of the sites
> where sgx_free_epc_page() is used in the driver. It does nothing to an
> uninitialized pages.
> 
> The two patches that I posted originally for Kai's series took EREMOVE out
> of sgx_free_epc_page() and put an explicit EREMOVE where it is actually
> needed, but for reasons unknown to me, that change is gone.
> 
> Replacing the ad-hoc code with sgx_free_epc_page() is absolutely the right
> action to take because it follows the pattern how sgx_free_epc_page() is
> used in the driver.

That sounds generally fine.  But, this is a functional change.  Where
there are functional changes, I always hope to see some mention of the
change in the changelog.

Could you add some of this to the next changelog, please?