Re: [RFC PATCH v3 03/27] x86/sgx: Remove a warn from sgx_free_epc_page()

Kai Huang
2021-01-27T05:05:10Z

On Tue, 2021-01-26 at 07:39 -0800, Dave Hansen wrote:
> On 1/26/21 1:30 AM, Kai Huang wrote:
> > Remove SGX_EPC_PAGE_RECLAIMER_TRACKED check and warning. This cannot
> > happen, as enclave pages are freed only at the time when encl->refcount
> > triggers, i.e. when both VFS and the page reclaimer have given up on
> > their references.
> >
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > Signed-off-by: Kai Huang <kai.huang@intel.com>
> > ---
> >  arch/x86/kernel/cpu/sgx/main.c | 2 --
> >  1 file changed, 2 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> > index 8df81a3ed945..f330abdb5bb1 100644
> > --- a/arch/x86/kernel/cpu/sgx/main.c
> > +++ b/arch/x86/kernel/cpu/sgx/main.c
> > @@ -605,8 +605,6 @@ void sgx_free_epc_page(struct sgx_epc_page *page)
> >   struct sgx_epc_section *section = &sgx_epc_sections[page->section];
> >   int ret;
> >
> >
> > - WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED);
>
> I'm all for cleaning up silly, useless warnings. But, don't we usually
> put warnings in for things that we don't expect to be able to happen?
>
> In other words, I'm fine with removing this if it hasn't been a valuable
> warning and we don't expect it to become a valuable warning. But, the
> changelog doesn't say that. It also doesn't explain what this patch is
> doing in this series.
>
> Why is this her?

Hi Jarkko,

I don't have deep understanding of SGX driver. Would you help to answer?