Re: [PATCH 0/3] PCI: designware: Fixing MSI handling flow

[Niklas Cassel <niklas.cassel@linaro.org>]

On Wed, Nov 21, 2018 at 07:24:53PM +0200, Stanimir Varbanov wrote:
> Hi,
> 
> On 11/14/18 12:57 AM, Marc Zyngier wrote:
> > It recently came to light that the Designware PCIe driver is rather
> > broken in the way it handles MSI[1]:
> > 
> > - It masks interrupt by disabling them, meaning that MSIs generated
> >   during the masked window are simply lost. Oops.
> > 
> > - Acking of the currently pending MSI is done outside of the interrupt
> >   flow, getting moved around randomly and ultimately breaking the
> >   driver. Not great.
> > 
> > This series attempts to address this by switching to using the MASK
> > register for masking interrupts (!), and move the ack into the
> > appropriate callback, giving it a fixed place in the MSI handling
> > flow.
> > 
> > Note that this is only compile-tested on my arm64 laptop, as I'm
> > travelling and do not have the required HW to test it anyway. I'd
> > welcome both review and testing by the interested parties (dwc
> > maintainer and users affected by existing bugs).
> > 
> > Thanks,
> > 
> > 	M.
> > 
> > [1] https://patchwork.kernel.org/patch/10657987/
> > 
> > Marc Zyngier (3):
> >   PCI: designware: Use interrupt masking instead of disabling
> >   PCI: designware: Take lock when ACKing an interrupt
> >   PCI: designware: Move interrupt acking into the proper callback
> > 
> >  .../pci/controller/dwc/pcie-designware-host.c | 22 ++++++++++++-------
> >  1 file changed, 14 insertions(+), 8 deletions(-)
> > 
> 
> for pcie-qcom:
> 
> Tested-by: Stanimir Varbanov <svarbanov@mm-sol.com>

Hello PCI folks,

Since this is a real bug, we should try get a couple of Tested-by tags
before it's too late.
It would be nice if v4.20 was released without broken MSIs in this driver.

Personally I get confused just by looking at this mail thread.

I see 3 patches from Marc and a fix-up from Marc, but I also see
a patch from Gustavo, and another patch from Trent.

Is seems like Lorenzo has a branch with Marc's 3 patches + Marc's fix-up
folded in here:
https://git.kernel.org/pub/scm/linux/kernel/git/lpieralisi/pci.git/log/?h=test%2Fpci-dwc-msi

Perhaps it would be a good idea to send a V2, with proper Fixes-tags,
just so that people would know what to test, so that we can start getting
those Tested-by tags.

Stan, may I ask exactly what patches you tested?


Kind regards,
Niklas