Messages in this thread | | | Subject | Re: [Part1 PATCH v4 15/17] percpu: introduce DEFINE_PER_CPU_UNENCRYPTED | From | Brijesh Singh <> | Date | Wed, 20 Sep 2017 11:16:10 -0500 |
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On 09/20/2017 02:34 AM, Borislav Petkov wrote: > On Tue, Sep 19, 2017 at 08:50:20AM -0500, Brijesh Singh wrote: >> "..shared_aligned" section does not start and end with page-size alignment. > > Nowhere in the code there's a comment saying: "This percpu section really must > be page-size aligned because <reasons>." You need to be more verbose > with requirements like that. >
I will add that comment.
> Also, you're ending up needing a whole page per-CPU for those variables. > And now with the alignment before and after, you have worst-case two > pages fragmentation of percpu memory and percpu memory is a rather > limited resource AFAIR. > > If only there were a alloc_percpu_page()... > >> Since the C-bit works on PAGE_SIZE alignment hence the "..unencrypted" section > > Btw, call that section "..decrypted" and everywhere do > s/unencrypted/decrypted/g. >
Will do
>> starts and ends with page-size alignment. The closest I can find is >> "..page_aligned" but again it does not end with page-size alignment. >> >> Additionally, since we clear the C-bit from unencrypted section hence we >> should avoid overloading the existing section -- we don't want to expose more >> than we wish. > > Add that to the comment too. >
Will do
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