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

From: Marc Zyngier <marc.zyngier@arm.com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Cc: linux-pci@vger.kernel.org, Bjorn Helgaas <helgaas@google.com>,
	Trent Piepho <tpiepho@impinj.com>,
	Jingoo Han <jingoohan1@gmail.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, 10 Dec 2018 16:30:44 +0000	[thread overview]
Message-ID: <c822907a-281e-fd3a-70bc-5fef4a500621@arm.com> (raw)
In-Reply-To: <20181210161753.GA12563@e107981-ln.cambridge.arm.com>

Hi Lorenzo,

On 10/12/2018 16:17, Lorenzo Pieralisi wrote:
> On Tue, Nov 13, 2018 at 10:57:31PM +0000, 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(-)
> 
> Marc, Gustavo,
> 
> I have decided to queue this series - fixed-up as per this thread,
> available at:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/lpieralisi/pci.git test/pci-dwc-msi
> 
> We allowed enough time for people to test it, we can't leave mainline
> broken for the, apparently few, people who care.
> 
> I *think* that this is the Fixes: tag to be added to all patches in this
> series, @Gustavo please countercheck:
> 
> 7c5925afbc58 ("PCI: dwc: Move MSI IRQs allocation to IRQ domains
> hierarchical API")
> 
> I will mark them for stable too and we will work on backports to be
> sent in due course.

Thanks for doing that Lorenzo. I'll work on a backport of the last patch
as soon as this hits mainline.

Cheers,

	M.
-- 
Jazz is not dead. It just smells funny...