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

[Haitao Huang]

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