Re: [PATCH] PCI/MSI: Avoid torn updates to MSI pairs

[Thomas Gleixner]

Evan Green <evgreen@xxxxxxxxxxxx> writes:
> On Thu, Jan 23, 2020 at 12:42 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>> Hrm:
>>
>>         Capabilities: [80] MSI-X: Enable+ Count=16 Masked-
>>
>> So this is weird. We mask it before moving it, so the tear issue should
>> not happen on MSI-X. So the tearing might be just a red herring.
>
> Mmm... sorry what? This is the complete entry for xhci:
>
> 00:14.0 USB controller: Intel Corporation Device 02ed (prog-if 30 [XHCI])
>         Subsystem: Intel Corporation Device 7270
>         Control: I/O- Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop-
> ParErr- Stepping- SERR- FastB2B- DisINTx+
>         Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium
>>TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
>         Interrupt: pin A routed to IRQ 124
>         Region 0: Memory at d1200000 (64-bit, non-prefetchable) [size=64K]
>         Capabilities: [70] Power Management version 2
>                 Flags: PMEClk- DSI- D1- D2- AuxCurrent=375mA
> PME(D0-,D1-,D2-,D3hot+,D3cold+)
>                 Status: D3 NoSoftRst+ PME-Enable+ DSel=0 DScale=0 PME-
>         Capabilities: [80] MSI: Enable+ Count=1/8 Maskable- 64bit+
>                 Address: 00000000fee10004  Data: 402a
>         Capabilities: [90] Vendor Specific Information: Len=14 <?>
>         Kernel driver in use: xhci_hcd

Bah. I was looking at the WIFI for whatever reason.

Thanks,

        tglx