Re: [PATCH v7 00/13] Support PPTT for ARM64

[Jeremy Linton]

Hi,

First thanks for testing this!!

On 03/08/2018 09:59 AM, Ard Biesheuvel wrote:
> On 27 February 2018 at 18:49, Jeremy Linton <jeremy.linton@xxxxxxx> wrote:
> > On 03/01/2018 06:06 AM, Sudeep Holla wrote:
> > > Hi Jeremy,
> > >
> > > On 28/02/18 22:06, Jeremy Linton wrote:
> > > > ACPI 6.2 adds the Processor Properties Topology Table (PPTT), which is
> > > > used to describe the processor and cache topology. Ideally it is
> > > > used to extend/override information provided by the hardware, but
> > > > right now ARM64 is entirely dependent on firmware provided tables.
> > > >
> > > > This patch parses the table for the cache topology and CPU topology.
> > > > When we enable ACPI/PPTT for arm64 we map the physical_id to the
> > > > PPTT node flagged as the physical package by the firmware.
> > > > This results in topologies that match what the remainder of the
> > > > system expects. To avoid inverted scheduler domains we then
> > > > set the MC domain equal to the largest cache within the socket
> > > > below the NUMA domain.
> > > I remember reviewing and acknowledging most of the cacheinfo stuff with
> > > couple of minor suggestions for v6. I don't see any Acked-by tags in
> > > this series and don't know if I need to review/ack any more cacheinfo
> > > related patches.
> >
> >
> > Hi,
> >
> > Yes, I didn't put them in because I changed the functionality in 2/13 and
> > there is a bug fix in 5/13. I thought you might want to do a quick diff of
> > the git v6->v7 tree.
> >
> > Although given that most of the changes were in response to your comments in
> > v6 I probably should have just put the tags in.
>
> I get sane output from lstopo when applying these patches and booting
> my Socionext SynQuacer in ACPI mode:
>
> $ lstopo-no-graphics
> Machine (31GB)
>    Package L#0 + L3 L#0 (4096KB)
>      L2 L#0 (256KB)
>        L1d L#0 (32KB) + L1i L#0 (32KB) + Core L#0 + PU L#0 (P#0)
>        L1d L#1 (32KB) + L1i L#1 (32KB) + Core L#1 + PU L#1 (P#1)
>      L2 L#1 (256KB)
>        L1d L#2 (32KB) + L1i L#2 (32KB) + Core L#2 + PU L#2 (P#2)
>        L1d L#3 (32KB) + L1i L#3 (32KB) + Core L#3 + PU L#3 (P#3)
>      L2 L#2 (256KB)
>        L1d L#4 (32KB) + L1i L#4 (32KB) + Core L#4 + PU L#4 (P#4)
>        L1d L#5 (32KB) + L1i L#5 (32KB) + Core L#5 + PU L#5 (P#5)
>      L2 L#3 (256KB)
>        L1d L#6 (32KB) + L1i L#6 (32KB) + Core L#6 + PU L#6 (P#6)
>        L1d L#7 (32KB) + L1i L#7 (32KB) + Core L#7 + PU L#7 (P#7)
>      L2 L#4 (256KB)
>        L1d L#8 (32KB) + L1i L#8 (32KB) + Core L#8 + PU L#8 (P#8)
>        L1d L#9 (32KB) + L1i L#9 (32KB) + Core L#9 + PU L#9 (P#9)
>      L2 L#5 (256KB)
>        L1d L#10 (32KB) + L1i L#10 (32KB) + Core L#10 + PU L#10 (P#10)
>        L1d L#11 (32KB) + L1i L#11 (32KB) + Core L#11 + PU L#11 (P#11)
>      L2 L#6 (256KB)
>        L1d L#12 (32KB) + L1i L#12 (32KB) + Core L#12 + PU L#12 (P#12)
>        L1d L#13 (32KB) + L1i L#13 (32KB) + Core L#13 + PU L#13 (P#13)
>      L2 L#7 (256KB)
>        L1d L#14 (32KB) + L1i L#14 (32KB) + Core L#14 + PU L#14 (P#14)
>        L1d L#15 (32KB) + L1i L#15 (32KB) + Core L#15 + PU L#15 (P#15)
>      L2 L#8 (256KB)
>        L1d L#16 (32KB) + L1i L#16 (32KB) + Core L#16 + PU L#16 (P#16)
>        L1d L#17 (32KB) + L1i L#17 (32KB) + Core L#17 + PU L#17 (P#17)
>      L2 L#9 (256KB)
>        L1d L#18 (32KB) + L1i L#18 (32KB) + Core L#18 + PU L#18 (P#18)
>        L1d L#19 (32KB) + L1i L#19 (32KB) + Core L#19 + PU L#19 (P#19)
>      L2 L#10 (256KB)
>        L1d L#20 (32KB) + L1i L#20 (32KB) + Core L#20 + PU L#20 (P#20)
>        L1d L#21 (32KB) + L1i L#21 (32KB) + Core L#21 + PU L#21 (P#21)
>      L2 L#11 (256KB)
>        L1d L#22 (32KB) + L1i L#22 (32KB) + Core L#22 + PU L#22 (P#22)
>        L1d L#23 (32KB) + L1i L#23 (32KB) + Core L#23 + PU L#23 (P#23)
>    HostBridge L#0
>      PCIBridge
>        PCIBridge
>          PCI 1b21:0612
>            Block(Disk) L#0 "sda"
>    HostBridge L#3
>      PCI 10de:128b
>        GPU L#1 "renderD128"
>        GPU L#2 "card0"
>        GPU L#3 "controlD64"
>
> So
>
> Tested-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>
> *However*, while hacking on the firmware that exposes the table, I
> noticed that a malformed structure (incorrect size) can get the parser
> in an infinite loop, hanging the boot after
>
> [    8.244281] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
> [    8.251780] Serial: AMBA driver
> [    8.255042] msm_serial: driver initialized
> [    8.259752] ACPI PPTT: Cache Setup ACPI cpu 0
> [    8.264121] ACPI PPTT: Looking for data cache
> [    8.268484] ACPI PPTT: Looking for CPU 0's level 1 cache type 0
>
> so I guess the parsing code could be made a bit more robust?

I've been wondering how long it would take for someone to complain about 
one of these cases, I added a check in find_processor_node back a few 
revisions ago to deal with zero length's causing infinite loops, but the 
leaf node check doesn't have one, and that is likely what your hitting.