On Fri, Jan 22, 2010 at 11:56:44PM +0800, Liu, Jinsong wrote:
> Gleb Natapov wrote:
> > On Fri, Jan 22, 2010 at 10:52:29PM +0800, Liu, Jinsong wrote:
> >> Gleb Natapov wrote:
> >>> On Fri, Jan 22, 2010 at 06:54:42PM +0800, Liu, Jinsong wrote:
> >>>> Gleb Natapov wrote:
> >>>>> On Fri, Jan 22, 2010 at 05:08:32PM +0800, Liu, Jinsong wrote:
> >>>>>> Gleb Natapov wrote:
> >>>>>>> On Fri, Jan 22, 2010 at 10:15:44AM +0800, Liu, Jinsong wrote:
> >>>>>>>> Gleb Natapov wrote:
> >>>>>>>>> On Thu, Jan 21, 2010 at 07:48:23PM +0800, Liu, Jinsong wrote:
> >>>>>>>>>>> From cb997030cba02e7e74a29b3d942aeba9808ed293 Mon Sep 17
> >>>>>>>>>>> 00:00:00 2001
> >>>>>>>>>> From: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
> >>>>>>>>>> Date: Fri, 22 Jan 2010 03:18:46 +0800
> >>>>>>>>>> Subject: [PATCH] Setup vcpu add/remove
> >>>>>>>>>> infrastructure, including madt bios_info and dsdt.
> >>>>>>>>>>
> >>>>>>>>>> 1. setup madt bios_info structure, so that static
> >>>>>>>>>> dsdt get run-time madt info like checksum
> >>>>>>>>>> address, lapic address, max cpu numbers, with
> >>>>>>>>>> least hardcode magic number (realmode address of
> >>>>>>>>>> bios_info).
> >>>>>>>>>> 2. setup vcpu add/remove dsdt infrastructure,
> >>>>>>>>>> including processor related acpi objects and
> >>>>>>>>>> control methods. vcpu add/remove will trigger SCI
> >>>>>>>>>> and then control method _L02. By matching madt,
> >>>>>>>>>> vcpu number and add/remove action were found,
> >>>>>>>>>> then by notify control
> >>>>>>>>>> method, it will notify OS acpi driver.
> >>>>>>>>>>
> >>>>>>>>>> Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
> >>>>>>>>> It looks like AML code is a port of what we had in BOCHS bios
> >>>>>>>>> with minor changes. Can you detail what is changed and why for
> >>>>>>>>> easy review please? And this still doesn't work with Windows
> >>>>>>>>> I assume.
> >>>>>>>>>
> >>>>>>>>
> >>>>>>>> Yes, my work is based on BOCHS infrastructure, thanks BOCHS :)
> >>>>>>>> I just change some minor points:
> >>>>>>>> 1. explicitly define returen value of '_MAT' as 'buffer',
> >>>>>>>> otherwise some linux acpi driver (i.e. linux 2.6.30) would
> >>>>>>>> parse error which will handle it as 'integer' not 'buffer';
> >>>>>>>> 2. keep correct 'checksum' of madt when vcpu add/remove,
> >>>>>>>> otherwise it will report 'checksum error' when using acpi tools
> >>>>>>>> to get madt info if we add/remove vcpu;
> >>>>>>>> 3. add '_EJ0' so that linux has acpi obj under
> >>>>>>>> /sys/devices/LNXSYSTM:00, which is need for vcpu remove;
> >>>>>>>> 4. on Method(PRSC, 0), just scan 'xxx' vcpus that qemu get from
> >>>>>>>> cmdline para 'maxcpus=xxx', not all 256 vcpus, otherwise under
> >>>>>>>> some dsdt processor define, it will result error;
> >>>>>>> What kind of errors? Qemu should never set bit over maxcpus in
> >>>>>>> PRS.
> >>>>>>>
> >>>>>> suppose cmdline define vcpus=4, maxvcpus=8
> >>>>>> in original BOCHS, will scan 15 lapic items start from lapic0 of
> >>>>>> madt, where it only has maxvcpus lapic items in madt table, hence
> >>>>>> there is risk to scan over boundary, scan to other acpi table,
> >>>>>> and result in wrong vcpu online/offline status (in my test, I
> >>>>>> meet this situation). Because of this reason, this patch limit
> >>>>>> scan maxvcpus lapic of madt.
> >>>>>>
> >>>>> But what if cmdline will use vcpu=64? The idea was that \_PR scope
> >>>>> will reside in its own ssdt and for each maxvcpus value there will
> >>>>> be ssdt with exactly this number of processors. Ideally ssdt will
> >>>>> be created dynamically like it is done now, but another solution
> >>>>> is to create them at bios compilation time and load correct one
> >>>>> at runtime.
> >>>>>
> >>>>
> >>>> It's OK for vcpu=64. vcpu<maxvcpus.
> >>>> if maxvcpus > processor defined in dsdt, it's OK since no risk scan
> >>>> (bios only support 15 processor is another story); if processor
> >>>> defined in dsdt > maxvcpus, it has risk to scan over boundary.
> >>>>
> >>>>
> >>> Yes, correct. So why not export maxcpus to DSDT and at the beginning
> >>> of NTFY check that Arg0 < maxcpus then?
> >>>
> >>
> >> Yes, your solution also work.
> >> In fact, we implicitly export maxcpus to DSDT by
> >> struct bios_info {
> >> ...
> >> u32 max_cpus_byte; /* max cpus bitmap bytes */
> >> u32 max_cpus_bit; /* max cpus bitmap bits of last byte */ };
> >> this indicate maxvcpus.
> >> In this way it can reduce scan loop.
> >>
> > Actually your scan loop is twice as big as it was in BOCHS because of
> > this tricks with bytes and bits.
> >
>
> No,
> original BOCHS solution: PRSC has 256 loop, and NTFY has 15 scan;
> this patch solution: PRSC has maxvcpus loop, and NTFY has min(15, maxvcpus) scan.
>
>
I what code to be shorter and easier to read, not optimize loop that
will be executed once in a blue moon.
> >> However, I think it's not key issue. Both are OK.
> >> Just different implement way.
> >>
> > The AML code is hard to read as it is, so making it simpler is
> > important. But the way I want to see this solved in seabios is to
> > create exactly maxvcpu processors in _PR scope. This will solve MS
> > SVVP problem too (BOCHS doesn't pass SVVP).
>
> Yes, to create exactly maxvcpu processor is key points.
>
--
Gleb.
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