Re: [ros-dev] Merging our x86 HALs

[Magnus Johnsson]

(Outsider looking in, again. hello. Ignore me if needed)

It seems to me like you are discussing this from a pretty nebulous sense of
'why should we do this' and the same for 'we are scared of doing this'.
So, concrete question, what sort of issues are you likely to run in to? You
have had issues now with bugs that pop up only on some HAL's due to
duplication of code. What are the negative consequences of doing this? What
could potentially break? Why would really old hardware break, and can it be
mitigated? And, if shit hits the fan, how hard would it be to backtrack
again/make a dirty as hell hack at runtime?

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2017-12-13 12:49 GMT+01:00 Javier Agustìn Fernàndez Arroyo &lt;elhoir(a)gmail.com
>  : 
>   "supporting very old hardware, which I see as a
> plain and simple waste of
>  resources."
>  I completely disagree.
>
>  Supporting very old hardware  means that it will consume very very fewer
>  resources in very new hardware, too.
>  But, speaking about the former, it would be wonderful to be able to run
>  Windows software in such hardware.
>
>  The question in this last case is, how HAL supports new CPU instructions?
>  but that`s an off-topic question
>
>  On Wed, Dec 13, 2017 at 8:24 AM, Riccardo Paolo Bestetti <
>  riccardo.kyogre(a)live.it&gt; wrote:
>
> >   Hi David,
> >
> >
> >
> >  I was talking about supporting very old hardware, which I see as a plain
> >  and simple waste of resources. There may be legacy computers running legacy
> >  software around, but you can be sure that no one is gonna redeploy these
> >  computer, especially with a different software configuration (i.e.
> >  installing ReactOS instead of Windows [2000|XP|2003] on it). Of course I
> >  leave the (very) technical discussion about how to implement HALs to you.
> >
> >
> >
> >  BR.
> >
> >  *Riccardo P. Bestetti*
> >
> >
> >
> >  *From:* Ros-dev [mailto:[e-mail]] *On Behalf Of *David
> >  Quintana (gigaherz)
> >  *Sent:* martedì 12 dicembre 2017 22:45
> >
> >  *To:* ReactOS Development List &lt;ros-dev(a)reactos.org&gt;
> >  *Subject:* Re: [ros-dev] Merging our x86 HALs
> >
> >
> >
> >  I think yes, on the fact that duplicate code is already causing bugs. Now
> >  wether we want to unify everything into one megaHAL, or compile multiple
> >  HALs fom the same codebase, or merge into two medium-sized HALs, that's
> >  what the discussion is meant to be about.
> >
> >
> >
> >  On 12 December 2017 at 22:00, Riccardo Paolo Bestetti <
> >  riccardo.kyogre(a)live.it&gt; wrote:
> >
> >  My bi-annual IT guy peak:
> >
> >
> >
> >  Is there a real need to?
> >
> >  I think not.
> >
> >
> >
> >  B.R.
> >
> >  *Riccardo P. Bestetti*
> >
> >
> >
> >  *From:* Ros-dev [mailto:[e-mail]] *On Behalf Of *Javier
> >  Agustìn Fernàndez Arroyo
> >  *Sent:* martedì 12 dicembre 2017 18:13
> >  *To:* ReactOS Development List &lt;ros-dev(a)reactos.org&gt;
> >  *Subject:* Re: [ros-dev] Merging our x86 HALs
> >
> >
> >
> >  Win8 does not support old hardware as ReactOS do!
> >
> >
> >
> >  El 12 dic. 2017 17:52, "Alex Ionescu" &lt;ionucu(a)videotron.ca&gt; escribió:
> >
> >  I would move to the Win8+ HAL Model -- a single HAL for APIC, ACPI with
> >  runtime support for UEFI (if present) and MP (if present).
> >
> >
> >
> >  If people still want to run on a PIC VM (why???) or old computer, then we
> >  can also maintain the HAL PIC x86 for UP.
> >
> >
> >
> >  Hence there would only be 2 HALs.
> >
> >
> >  Best regards,
> >  Alex Ionescu
> >
> >
> >
> >  On Mon, Dec 11, 2017 at 1:07 AM, Colin Finck &lt;colin(a)reactos.org&gt; wrote:
> >
> >  Am 11.12.2017 um 01:18 schrieb Hermès BÉLUSCA-MAÏTO:> If you basically
> >  put all the HALs into one, then you obtain bloated stuff (which remains
> >  in memory for the whole life of the OS). Example: standard HAL is 1MB
> >  vs. ACPI HAL which is few kBHave you actually checked what makes up this
> >  difference?
> >  Hint: hal/halx86/legacy/bus/pci_vendors.ids
> >
> >
> > >   Note that if Windows nowadays has only one hal,
> > > it's because they now 
> >  support basically only one
> > "architecture"/platform, namely, ACPI
> >  multiprocessor (to put it simple). It has its pros, but also a lot of cons.
> >
> >  That doesn't mean we need to do the same. We can have one HAL for all
> >  (Pentium and newer) x86 platforms. The overhead of additional checks at
> >  boot-up is negligible. That should be a solution for 99% of the people
> >  out there. The rest may still go and trim down our HAL to their needs.
> >
> >  But let's not pretend we can maintain multiple x86 HALs for all x86
> >  computers out there. Do you really want to test X HALs with Y different
> >  systems? Ensure that a legacy HAL runs on a modern ACPI system? What
> >  would be the point?
> >
> >
> > >   Besides this, I've a question about your
> > > observation that in the APIC 
> >  hal (not ACPI) there's different implementation
> > of
> >  HalpCalibrateStallExecution and HalpInitializePICs /
> >  HalpInitializeLegacyPIC . Isn't it precisely because these stuff are
> >  completely different from the standard PICs used in platforms for which the
> >  standard HAL (and possibly the ACPI HAL) are used?
> >
> >  Absolutely not! You need to reprogram the standard PICs also on an APIC
> >  system, and this is precisely what both functions do. Put them into a
> >  diff tool to see for yourself.
> >
> >  The same goes for timers. Even with the introduction of ACPI Timers,
> >  Local APIC Timers, and Time-Stamp Counters, you still need a traditional
> >  one (like RTC or PIT) for calibration at system startup. Simply because
> >  the newer ones don't run at a known fixed frequency.
> >  The Legacy HAL successfully employs an algorithm based on the RTC while
> >  the APIC HAL unsuccessfully tries to use the PIT.
> >
> >
> > >   Actually we should, because the detection might
> > > not work (of course in 
> >  our simple case "ACPI UP/MP" vs.
> > "Standard", it's simple, but think about
> >  other platforms where there can be subtle differences)
> >
> >  Tell me about a single one we cannot detect and which is worth to
> >  support. I don't recall that we ever recommended our testers to choose a
> >  different HAL at setup.
> >
> >
> > >   And normally it's not the setup that decides
> > > about the HAL, but the 
> >  bootloader.
> >
> >  That defies your previous point about the setup initializing the
> >  registry depending on the HAL.
> >  If we can let the user select a Legacy HAL in the boot loader after
> >  installing with an ACPI HAL, it is also technically possible to have one
> >  HAL that encompasses both.
> >
> >
> >
> >  - Colin
> >
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