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

From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Niklas Cassel <niklas.cassel@linaro.org>
Cc: Stanimir Varbanov <svarbanov@mm-sol.com>,
	Marc Zyngier <marc.zyngier@arm.com>,
	linux-pci@vger.kernel.org, Bjorn Helgaas <helgaas@google.com>,
	Trent Piepho <tpiepho@impinj.com>,
	Jingoo Han <jingoohan1@gmail.com>,
	Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
	faiz_abbas@ti.com, Joao Pinto <Joao.Pinto@synopsys.com>,
	Vignesh R <vigneshr@ti.com>
Subject: Re: [PATCH 0/3] PCI: designware: Fixing MSI handling flow
Date: Mon, 3 Dec 2018 10:42:19 +0000	[thread overview]
Message-ID: <20181203104218.GB6090@e107981-ln.cambridge.arm.com> (raw)
In-Reply-To: <20181201235058.GA21020@centauri.lan>

On Sun, Dec 02, 2018 at 12:50:58AM +0100, Niklas Cassel wrote:
> 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.

Perhaps it would be a good idea to pull the branch above and test it
after I have sent three reminders to all DWC host bridge maintainers through
this email thread.

I have no problem reposting those patches but it is time you started
testing them, I have already explained what's the issue they are fixing
in this thread, I do not think a Fixes: tag will add any further degree
of urgency.

Thanks,
Lorenzo