Re: [RFC PATCH] x86/sgx: Remove 'reclaim' boolean parameters

From: Haitao Huang
Date: Mon Feb 19 2024 - 17:25:43 EST


On Mon, 19 Feb 2024 14:42:29 -0600, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote:

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.
>
> Also opportunistically remove non-static declaration of
> __sgx_alloc_epc_page() and a typo
>
> Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
> Suggested-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
> ---
> 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


Thanks. My understanding is:

1) For this patch, replace the boolean with the enum as Dave suggested. No two versions of the same functions. And this is a prerequisite for the cgroup series, positioned before [PATCH v9 04/15]

2) For [PATCH v9 04/15], pass a hard coded SGX_NO_RECLAIM to sgx_epc_cg_try_charge() from sgx_alloc_epc_page().

3) For [PATCH v9 10/15], remove the hard coded value, pass the reclaim enum parameter value from sgx_alloc_epc_page() to sgx_epc_cg_try_charge() and add the reclaim logic.

I'll send patches soon. But please let me know if I misunderstood.

Thanks
Haitao