On Mon, 2014-07-21 at 14:33 -0400, Konrad Rzeszutek Wilk wrote: > On Mon, Jul 21, 2014 at 10:32:34AM -0700, H. Peter Anvin wrote: > > On 07/21/2014 10:16 AM, Toshi Kani wrote: : > > > > >> I would also like a systematic way to deal with the fact > > >> that Xen (sigh) is stuck with a separate mapping system. > > >> > > >> I guess Linux could adopt the Xen mappings if that makes it easier, as > > >> long as that doesn't have a negative impact on native hardware -- we can > > >> possibly deal with some older chips not being optimal. > > > > > > I see. I agree that supporting the PAT bit is the right direction, but > > > I do not know how much effort we need. I will study on this. > > > > > >> However, my thinking has been to have a "reverse PAT" table in memory of memory > > >> types to encodings, both for regular and large pages. > > > > > > I am not clear about your idea of the "reverse PAT" table. Would you > > > care to elaborate? How is it different from using pte_val() being a > > > paravirt function on Xen? > > > > First of all, paravirt functions are the root of all evil, and we want > > Here I was thinking to actually put an entry in the MAINTAINERS > file for me to become the owner of it - as the folks listed there > are busy with other things. > > The Maintainer of 'All Evil' has an interesting ring to it :-) :-) > > to reduce and eliminate them to the utmost level possible. But yes, we > > could plumb that up that way if we really need to. > > > > What I'm thinking of is a table which can deal with both the moving PTE > > bit, Xen, and the scattered encodings by having a small table from types > > to encodings, and not use the encodings directly until fairly late it > > the pipe. I suspect, but I'm not sure, that we would also need the > > inverse operation. > > Mr Toshi-san, Oh, you are so polite, Wilk-san. > This link: http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/x86/hvm/mtrr.c;h=ee18553cdac58dd16836011ee714517fbc16368d;hb=HEAD#l74 might help you in figuring how this can be done. > > Thought I have to say that the code is quite complex so it might > be more confusing then helpful. Thanks again for the pointer! I will take a look. I used to work on a paravirt on other OS, but I am pretty much new to Xen. One more thing to learn. :-) -Toshi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>