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Date: Mon, 19 Feb 2024 20:42:29 +0000
Message-Id: <CZ9CIP97661C.2WUZJNNCQUHE8@seitikki>
Cc: <anakrish@microsoft.com>, <bp@alien8.de>, <cgroups@vger.kernel.org>,
 <chrisyan@microsoft.com>, <dave.hansen@linux.intel.com>, <hpa@zytor.com>,
 <kristen@linux.intel.com>, <linux-kernel@vger.kernel.org>,
 <linux-sgx@vger.kernel.org>, <mikko.ylinen@linux.intel.com>,
 <mingo@redhat.com>, <mkoutny@suse.com>, <seanjc@google.com>,
 <sohil.mehta@intel.com>, <tglx@linutronix.de>,
 <tim.c.chen@linux.intel.com>, <tj@kernel.org>, <x86@kernel.org>,
 <yangjie@microsoft.com>, <zhanb@microsoft.com>, <zhiquan1.li@intel.com>
Subject: Re: [RFC PATCH] x86/sgx: Remove 'reclaim' boolean parameters
From: "Jarkko Sakkinen" <jarkko@kernel.org>
To: "Dave Hansen" <dave.hansen@intel.com>, "Haitao Huang"
 <haitao.huang@linux.intel.com>
References: <CZ4FCQ633VLC.26Y7HUHGRSFB3@kernel.org>
 <20240219153957.9957-1-haitao.huang@linux.intel.com>
 <40f95b90-8698-42dd-89d7-cd73d1e311b1@intel.com>
In-Reply-To: <40f95b90-8698-42dd-89d7-cd73d1e311b1@intel.com>

On Mon Feb 19, 2024 at 3:56 PM UTC, Dave Hansen wrote:
> On 2/19/24 07:39, Haitao Huang wrote:
> > Remove all boolean parameters for 'reclaim' from the function
> > sgx_alloc_epc_page() and its callers by making two versions of each
> > function.
> >=20
> > Also opportunistically remove non-static declaration of
> > __sgx_alloc_epc_page() and a typo
> >=20
> > Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
> > Suggested-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> >  arch/x86/kernel/cpu/sgx/encl.c  | 56 +++++++++++++++++++++------
> >  arch/x86/kernel/cpu/sgx/encl.h  |  6 ++-
> >  arch/x86/kernel/cpu/sgx/ioctl.c | 23 ++++++++---
> >  arch/x86/kernel/cpu/sgx/main.c  | 68 ++++++++++++++++++++++-----------
> >  arch/x86/kernel/cpu/sgx/sgx.h   |  4 +-
> >  arch/x86/kernel/cpu/sgx/virt.c  |  2 +-
> >  6 files changed, 115 insertions(+), 44 deletions(-)
>
> Jarkko, did this turn out how you expected?
>
> I think passing around a function pointer to *only* communicate 1 bit of
> information is a _bit_ overkill here.
>
> Simply replacing the bool with:
>
> enum sgx_reclaim {
> 	SGX_NO_RECLAIM,
> 	SGX_DO_RECLAIM
> };
>
> would do the same thing.  Right?
>
> Are you sure you want a function pointer for this?

To look this in context I drafted quickly two branches representing
imaginary next version of the patch set.

I guess this would simpler and totally sufficient approach.

With this approach I'd then change also:

[PATCH v9 04/15] x86/sgx: Implement basic EPC misc cgroup functionality

And add the enum-parameter already in that patch with just "no reclaim"
enum. I.e. then 10/15 will add only "do reclaim" and the new
functionality.

BR, Jarkko