On Mon, Sep 03, 2018 at 09:25:43AM +0200, Roman Kapl wrote: > > On 08/31/2018 05:35 AM, David Gibson wrote: > > On Tue, Aug 14, 2018 at 06:59:54PM +0200, Roman Kapl wrote: > > > External PID is a mechanism present on BookE 2.06 that enables > > > application to > > > store/load data from different address spaces. There are special version > > > of some > > > instructions, which operate on alternate address space, which is > > > described in > > > the EPLC/EPSC regiser. > > > > > > This implementation uses two additional MMU modes (mmu_idx) to provide the > > > address space for the load and store instructions. The QEMU TLB fill code > > > was > > > modified to recognize these MMU modes and use the values in EPLC/EPSC to > > > find > > > the proper entry in he PPC TLB. These two QEMU TLBs are also flushed on > > > each > > > write to EPLC/EPSC. > > > > > > Following instructions are implemented: dcbfep dcbstep dcbtep dcbtstep > > > dcbzep > > > dcbzlep icbiep lbepx ldepx lfdepx lhepx lwepx stbepx stdepx stfdepx sthepx > > > stwepx. > > > > > > Following vector instructions are not: evlddepx evstddepx lvepx lvepxl > > > stvepx > > > stvepxl. > > > > > > Signed-off-by: Roman Kapl <r...@sysgo.com> > > > > Looks like a good first draft. I have a few comments dispersed below. > > > > On a more general level, I'm not totally clear on how the new mmu > > indices work. AIUI these essentially index different qemu TLBs (as > > opposed to modelled hardware TLBs). If the EP was set to the same PID > > as the current process you'd have two indices essentially aliased to > > each other - in that case do we have all the necessary flushes in > > place? > > That is a good point (i assume you mean QEMU TLB flush). The existing code > seems to always call tlb_flush, not tlb_flush_mmuidx, so it should wipe out > all QEMU TLBs, including the EPID ones, whenever the HW TLB changes. You > could already have this aliasing even without EPID in the different TLB > modes for supervisor/user etc. Can you think of any other reasons why the > aliasing would be a problem?
Hm, no, I guess you're right. I can't say I understand the mmuidx
stuff as well as I'd like, but I think your approach should work.
I'll await v2.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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