linux-kernel - Re: [PATCH v3 2/2] x86/sgx: Add SGX

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Date:   Sat, 28 Aug 2021 00:03:35 +1200
From:   Kai Huang <kai.huang@...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>,
        Jonathan Corbet <corbet@....net>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 2/2] x86/sgx: Add SGX_MemTotal to /proc/meminfo


> > > -/* The free page list lock protected variables prepend the lock. */
> > > +/* The number of usable EPC pages in the system. */
> > > +unsigned long sgx_nr_all_pages;
> > > +
> > > +/* The number of free EPC pages in all nodes. */
> > >  static unsigned long sgx_nr_free_pages;
> > >  
> > >  /* Nodes with one or more EPC sections. */
> > > @@ -656,6 +659,8 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
> > >  		list_add_tail(&section->pages[i].list, &sgx_dirty_page_list);
> > >  	}
> > >  
> > > +	sgx_nr_all_pages += nr_pages;
> > > +
> > 
> > EPC sections can be freed again in sgx_init() after they are successfully
> > initialized, when any further initialization fails (i.e. when fails to create
> > ksgxd, or fails to register /dev/sgx_provision).  In which case, I think
> > sgx_nr_all_pages should also be cleared.  But current sgx_init() seems doesn't
> > reset it.  Do you need to fix that too?
> 
> sgx_nr_all_pages tells just the total pages in the system, i.e. it's a constant.
> 
> Maybe a rename to "sgx_nr_total_pages" would be a good idea? Would match with
> the meminfo field better too.

I don't have preference on name.  I just think if there's no actual user of
EPC (when both driver and KVM SGX cannot be enabled), it's pointless to print
number of EPC pages.

> 
> > 
> > >  	return true;
> > >  }
> > >  
> > > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> > > index ad8a5c586a35..82bb09c298de 100644
> > > --- a/arch/x86/mm/pat/set_memory.c
> > > +++ b/arch/x86/mm/pat/set_memory.c
> > > @@ -29,6 +29,7 @@
> > >  #include <asm/proto.h>
> > >  #include <asm/memtype.h>
> > >  #include <asm/set_memory.h>
> > > +#include <asm/sgx.h>
> > 
> > How about only include <asm/sgx.h> when CONFIG_X86_SGX is on, then you don't
> > have to do #ifdef CONFIG_X86_SGX changes to sgx.h?
> 
> Why do it that way instead of doing it once in sgx.h for every site that wants
> to include the file?

Just my preference.  You only need sgx_nr_all_pages here, while <asm/sgx.h>
has bunch of others such as SGX data structures.  It seems it's not worth to
include <asm/sgx.h> directly.