lkml.org 
[lkml]   [2017]   [Nov]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v6 06/11] intel_sgx: driver for Intel Software Guard Extensions
On Sun, Nov 26, 2017 at 09:01:09PM +0200, Jarkko Sakkinen wrote:
> On Sun, Nov 26, 2017 at 08:46:27PM +0200, Jarkko Sakkinen wrote:
> > On Sun, Nov 26, 2017 at 07:33:56PM +0200, Jarkko Sakkinen wrote:
> > > > +struct sgx_encl_page {
> > > > + unsigned long addr;
> > > > + unsigned int flags;
> > > > + void *epc_page;
> > > > + struct sgx_va_page *va_page;
> > > > + unsigned int va_offset;
> > > > + struct list_head list;
> > > > +};
> > >
> > > This can be without major streches hoops packed way more. There are 12
> > > bits free for use in the addr field. I can use low three bits for flags
> > > and upper nine bits for va_offset.
> > >
> > > I think I can also quite easily union epc_page and va_page fields.
> > >
> > > With these changes the struct would shrink to:
> > >
> > > struct sgx_encl_page {
> > > unsigned long addr;
> > > union {
> > > void *epc_page;
> > > struct sgx_va_page *va_page;
> > > };
> > > struct list_head list;
> > > };
> >
> > Once I started to thinking more about this I realized that this can be
> > shrunk even further. I can drop the list field and use a tag for loaded
> > pages in the radix tree where these are stored. The end result would be
> >
> > struct sgx_encl_page {
> > unsigned long addr;
> > union {
> > void *epc_page;
> > struct sgx_va_page *va_page;
> > };
> > };
>
> With this last size optimization there is an issue that it would be nice
> to select the pages to be swapped out in FIFO order. That kind of means
> that tag would not work quite well.
>
> I could try an approach where I have a pointer array to present a queue
> inside struct sgx_encl for loaded pages and in that way get rid of the
> 'list' field.

I did other optimizations except taking the list field away so it's now
a 32 byte structure. I guess sufficient for the first mainline version.

/Jarkko

\
 
 \ /
  Last update: 2017-11-29 19:12    [W:0.137 / U:1.548 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site