Re: [PATCH 3/3] xen/acpi: upload power and performance related data from a PVH dom0

[Josef Johansson <josef@oderland.se>]

On 3/15/23 12:39, Roger Pau Monné wrote:
> On Mon, Jan 30, 2023 at 10:10:05AM +0100, Josef Johansson wrote:
>> On 11/21/22 11:21, Roger Pau Monne wrote:
>>> When running as a PVH dom0 the ACPI MADT is crafted by Xen in order to
>>> report the correct numbers of vCPUs that dom0 has, so the host MADT is
>>> not provided to dom0.  This creates issues when parsing the power and
>>> performance related data from ACPI dynamic tables, as the ACPI
>>> Processor UIDs found on the dynamic code are likely to not match the
>>> ones crafted by Xen in the dom0 MADT.
>>>
>>> Xen would rely on Linux having filled at least the power and
>>> performance related data of the vCPUs on the system, and would clone
>>> that information in order to setup the remaining pCPUs on the system
>>> if dom0 vCPUs < pCPUs.  However when running as PVH dom0 it's likely
>>> that none of dom0 CPUs will have the power and performance data
>>> filled, and hence the Xen ACPI Processor driver needs to fetch that
>>> information by itself.
>>>
>>> In order to do so correctly, introduce a new helper to fetch the _CST
>>> data without taking into account the system capabilities from the
>>> CPUID output, as the capabilities reported to dom0 in CPUID might be
>>> different from the ones on the host.
>>>
>>>
>> Hi Roger,
>>
>> First of all, thanks for doing the grunt work here to clear up the ACPI
>> situation.
>>
>> A bit of background, I'm trying to get an AMD APU (CPUID 0x17 (23)) to work
>> properly
>> under Xen. It works fine otherwise but something is amiss under Xen.
> Hello,
>
> Sorry for the delay, I've been on paternity leave and just caching up
> on emails.
Hi Roger,

Congratulations! I hope you had time to really connect. It's the most 
important thing we can do here in life.

I came into this to understand each and every error in my boot-log, it 
turns out that the latest
kernel+xen+firmware fixes suspend/resume for me, thus is this not 
related. But as I pointed out,
the output does not make any sense (nor yours nor the upstream). I 
should check the debug
output with suspend working fine now to see if there are any changes, 
that would be quite
interesting.

Also, I should mention that your patch broke some things on my system 
and made it
unstable. I don't remember exactly and I know you said that this is more 
of a PoC. Just a
heads up.
>> Just to make sure that the patch is working as intended, what I found when
>> trying it out
>> is that the first 8 CPUs have C-States, but 0, 2, 4, 6, 8, 10, 12, 14 have
>> P-States, out of
>> 16 CPUs. Xen tells Linux that there are 8 CPUs since it's running with
>> nosmt.
>>
>> Regards
>> - Josef
>>
>> xen_acpi_processor: Max ACPI ID: 30
>> xen_acpi_processor: Uploading Xen processor PM info
>> xen_acpi_processor: ACPI CPU0 - C-states uploaded.
>> xen_acpi_processor:      C1: ACPI HLT 1 uS
>> xen_acpi_processor:      C2: ACPI IOPORT 0x414 18 uS
>> xen_acpi_processor:      C3: ACPI IOPORT 0x415 350 uS
>> xen_acpi_processor: ACPI CPU0 - P-states uploaded.
>> xen_acpi_processor:      *P0: 1700 MHz, 2071 mW, 0 uS
>> xen_acpi_processor:       P1: 1600 MHz, 1520 mW, 0 uS
>> xen_acpi_processor:       P2: 1400 MHz, 1277 mW, 0 uS
>> xen_acpi_processor: ACPI CPU1 - C-states uploaded.
>> xen_acpi_processor:      C1: ACPI HLT 1 uS
>> xen_acpi_processor:      C2: ACPI IOPORT 0x414 18 uS
>> xen_acpi_processor:      C3: ACPI IOPORT 0x415 350 uS
>> xen_acpi_processor: ACPI CPU2 - C-states uploaded.
>> xen_acpi_processor:      C1: ACPI HLT 1 uS
>> xen_acpi_processor:      C2: ACPI IOPORT 0x414 18 uS
>> xen_acpi_processor:      C3: ACPI IOPORT 0x415 350 uS
>> xen_acpi_processor: ACPI CPU2 - P-states uploaded.
>> xen_acpi_processor:      *P0: 1700 MHz, 2071 mW, 0 uS
>> xen_acpi_processor:       P1: 1600 MHz, 1520 mW, 0 uS
>> xen_acpi_processor:       P2: 1400 MHz, 1277 mW, 0 uS
>> xen_acpi_processor: ACPI CPU3 - C-states uploaded.
>> xen_acpi_processor:      C1: ACPI HLT 1 uS
>> xen_acpi_processor:      C2: ACPI IOPORT 0x414 18 uS
>> xen_acpi_processor:      C3: ACPI IOPORT 0x415 350 uS
>> xen_acpi_processor: ACPI CPU4 - C-states uploaded.
>> xen_acpi_processor:      C1: ACPI HLT 1 uS
>> xen_acpi_processor:      C2: ACPI IOPORT 0x414 18 uS
>> xen_acpi_processor:      C3: ACPI IOPORT 0x415 350 uS
>> xen_acpi_processor: ACPI CPU4 - P-states uploaded.
>> xen_acpi_processor:      *P0: 1700 MHz, 2071 mW, 0 uS
>> xen_acpi_processor:       P1: 1600 MHz, 1520 mW, 0 uS
>> xen_acpi_processor:       P2: 1400 MHz, 1277 mW, 0 uS
>> xen_acpi_processor: ACPI CPU5 - C-states uploaded.
>> xen_acpi_processor:      C1: ACPI HLT 1 uS
>> xen_acpi_processor:      C2: ACPI IOPORT 0x414 18 uS
>> xen_acpi_processor:      C3: ACPI IOPORT 0x415 350 uS
>> xen_acpi_processor: ACPI CPU6 - C-states uploaded.
>> xen_acpi_processor:      C1: ACPI HLT 1 uS
>> xen_acpi_processor:      C2: ACPI IOPORT 0x414 18 uS
>> xen_acpi_processor:      C3: ACPI IOPORT 0x415 350 uS
>> xen_acpi_processor: ACPI CPU6 - P-states uploaded.
>> xen_acpi_processor:      *P0: 1700 MHz, 2071 mW, 0 uS
>> xen_acpi_processor:       P1: 1600 MHz, 1520 mW, 0 uS
>> xen_acpi_processor:       P2: 1400 MHz, 1277 mW, 0 uS
>> xen_acpi_processor: ACPI CPU7 - C-states uploaded.
>> xen_acpi_processor:      C1: ACPI HLT 1 uS
>> xen_acpi_processor:      C2: ACPI IOPORT 0x414 18 uS
>> xen_acpi_processor:      C3: ACPI IOPORT 0x415 350 uS
>> xen_acpi_processor: ACPI CPU0 w/ PBLK:0x0
>> xen_acpi_processor: ACPI CPU0 w/ PST:coord_type = 254 domain = 0
>> xen_acpi_processor: CPU with ACPI ID 1 is unavailable
> Hm, that's weird, do you think you could check why it reports the CPU
> is unavailable?
If you would give me a hint at how I could check?
Right now my guess is that C state and P state is not in sync, thus P 
state are for every other
CPU and C state is for the first 8. AFAIK AMD only have 
performance-cores (unlike Intel).
>
> Overall I don't like the situation of the ACPI handling when running
> as dom0. It's fragile to rely on the data for dom0 CPUs to be
> filled by the system (by adding some band aids here and there so that
> the PV vCPUs are matched against the MADT objects) and then cloning
> the data for any physical CPU exceeding the number of dom0 virtual
> CPUs.
That's my understanding from earlier implementation as well, nobody 
actually like it,
But the current solution is something working in a bad environment.
>
> IMO it would be much better to just do the handling of ACPI processor
> objects in a Xen specific driver (preventing the native driver from
> attaching) in order to fetch the data and upload it to Xen.  This is
> what I've attempted to do on FreeBSD, and resulted in a cleaner
> implementation:
>
> <link>
>
> I however don't have time to do this right now for Linux.

Maybe I can take a stab, I very much like the climate of the kernel but 
everything
seem so scary :) I've been trying to understand things better, how 
they're all
connected.
>
>> xen_acpi_processor: ACPI CPU2 w/ PBLK:0x0
>> xen_acpi_processor: ACPI CPU2 w/ PST:coord_type = 254 domain = 1
>> xen_acpi_processor: CPU with ACPI ID 3 is unavailable
>> xen_acpi_processor: ACPI CPU4 w/ PBLK:0x0
>> xen_acpi_processor: ACPI CPU4 w/ PST:coord_type = 254 domain = 2
>> xen_acpi_processor: CPU with ACPI ID 5 is unavailable
>> xen_acpi_processor: ACPI CPU6 w/ PBLK:0x0
>> xen_acpi_processor: ACPI CPU6 w/ PST:coord_type = 254 domain = 3
>> xen_acpi_processor: CPU with ACPI ID 7 is unavailable
>> xen_acpi_processor: ACPI CPU8 w/ PBLK:0x0
>> xen_acpi_processor: ACPI CPU8 w/ PST:coord_type = 254 domain = 4
>> xen_acpi_processor: CPU with ACPI ID 9 is unavailable
>> xen_acpi_processor: ACPI CPU10 w/ PBLK:0x0
>> xen_acpi_processor: ACPI CPU10 w/ PST:coord_type = 254 domain = 5
>> xen_acpi_processor: CPU with ACPI ID 11 is unavailable
>> xen_acpi_processor: ACPI CPU12 w/ PBLK:0x0
>> xen_acpi_processor: ACPI CPU12 w/ PST:coord_type = 254 domain = 6
>> xen_acpi_processor: CPU with ACPI ID 13 is unavailable
>> xen_acpi_processor: ACPI CPU14 w/ PBLK:0x0
>> xen_acpi_processor: ACPI CPU14 w/ PST:coord_type = 254 domain = 7
>> xen_acpi_processor: CPU with ACPI ID 15 is unavailable
>> xen_acpi_processor: ACPI CPU8 - P-states uploaded.
>> xen_acpi_processor:      *P0: 1700 MHz, 2071 mW, 0 uS
>> xen_acpi_processor:       P1: 1600 MHz, 1520 mW, 0 uS
>> xen_acpi_processor:       P2: 1400 MHz, 1277 mW, 0 uS
>> xen_acpi_processor: ACPI CPU10 - P-states uploaded.
>> xen_acpi_processor:      *P0: 1700 MHz, 2071 mW, 0 uS
>> xen_acpi_processor:       P1: 1600 MHz, 1520 mW, 0 uS
>> xen_acpi_processor:       P2: 1400 MHz, 1277 mW, 0 uS
>> xen_acpi_processor: ACPI CPU12 - P-states uploaded.
>> xen_acpi_processor:      *P0: 1700 MHz, 2071 mW, 0 uS
>> xen_acpi_processor:       P1: 1600 MHz, 1520 mW, 0 uS
>> xen_acpi_processor:       P2: 1400 MHz, 1277 mW, 0 uS
>> xen_acpi_processor: ACPI CPU14 - P-states uploaded.
>> xen_acpi_processor:      *P0: 1700 MHz, 2071 mW, 0 uS
>> xen_acpi_processor:       P1: 1600 MHz, 1520 mW, 0 uS
>> xen_acpi_processor:       P2: 1400 MHz, 1277 mW, 0 uS
>>
>> As a bonus, here are the previous debug output on the same machine.
> I think the output below is with dom0 running as plain PV rather than
> PVH?
This is the upstream ACPI implementation vs yours. What would plain PV 
vs PVH be in dom0?

Regards
- Josef
> Thanks, Roger.