On 1/18/24 07:00, Nhi Pham wrote: > Hi Laszlo, > > On 1/16/2024 2:00 AM, Laszlo Ersek wrote: >> On 1/15/24 15:04, Ard Biesheuvel wrote: >>> On Mon, 15 Jan 2024 at 14:07, Nhi Pham <n...@os.amperecomputing.com> >>> wrote: >>>> >>>> On 1/12/2024 4:45 PM, Laszlo Ersek wrote: >>>>> (Independently: I think that's a valid thing to do for *SMM* drivers, >>>>> because the entry point functions of those drivers are permitted to >>>>> use >>>>> both SMM and DXE/UEFI protocols. But whether the same is valid for the >>>>> *standalone* MM drivers -- that looks questionable. Standalone MM >>>>> drivers should not depend on UEFI/DXE protocols ever, IIUC.) >>>>> >>>>>> 3) The issue is patching the grammar in place, why can’t we just >>>>>> make a >>>>>> copy for the dispatcher grammer, and operate on the copy. Maybe via a >>>>>> copy on 1st update strategy? >>>>> >>>>> Yes, copying the depex to the heap, and patching it there, was >>>>> Nhi's #1 >>>>> fix proposal. I think that could be made work. But I'm not sure if the >>>>> perf savings are worth the additional complexity. The heap allocation >>>>> (where the writeable depex would exist) would have to be permanently >>>>> associated with the loaded PE image -- because the dispatcher might >>>>> need >>>>> to reevaluate the depex across multiple rounds of dispatching. So >>>>> that's >>>>> a new field in some image-related structure, it also needs to be freed >>>>> upon unload (?), what if the memory allocation fails during depex eval >>>>> (just consider the depex to eval to FALSE?), etc. Doable, but >>>>> hairy; not >>>>> sure if the perf is worth that effort. >>>>> >>>> >>>> Thanks so much, Laszlo for your valuable insights. >>>> >>>> The approach #1 works for me. I will do further check for your concerns >>>> above. >>>> >>>> I'm trying your suggested patch and investigating the performance being >>>> discussed here. >>>> >>> >>> Not sure what approach #1 means, >> >> (copying the depex to the heap, and maintaining it there, so that it can >> be patched) > > Thanks! > >> >>> but I'd prefer to just remove this >>> optimization from standalone MM, given that not only a) it shouldn't >>> have to deal with a large number of protocol GUIDs, but also b) the >>> driver dispatch is much more straight-forward. (Typically, StMM >>> drivers can be dispatched in the order they appear in the firmware >>> volume, in which case each DEPEX is evaluated only once anyway) >> >> Sounds like a promising basis for removing the optimization indeed! >> > > Your patch suggested earlier works for me. And I don't see significant > performance reduction compared with keeping optimization. > > I don't have strong reason on removing the optimization, but I think it > would be simply good for now. Could you post your patch to edk2-devel > for review and merge?
That wouldn't be correct; I don't have any platform for testing StMM. I proposed the patch purely based on code analysis. I prefer not to post untested patches, if I can avoid it. You can however post my patch; simply add your S-o-b at the bottom. You can also preserve my authorship on the patch with --author=... on git-commit; but even that is unnecessary for such a simple patch (you don't even have to pick the patch up from the email, it's trivial to reimplement from scratch, just reading the email). Thanks Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#113994): https://edk2.groups.io/g/devel/message/113994 Mute This Topic: https://groups.io/mt/103594587/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/leave/9847357/21656/1706620634/xyzzy [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
