Messages in this thread | | | Date | Wed, 29 Nov 2017 20:02:32 +0200 | From | Jarkko Sakkinen <> | Subject | Re: [PATCH v6 06/11] intel_sgx: driver for Intel Software Guard Extensions |
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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
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