linux-kernel - Re: [RFC 10/10] tools: PCI: Add MSI-X support

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Date:   Tue, 24 Apr 2018 18:18:55 +0100
From:   Gustavo Pimentel <gustavo.pimentel@...opsys.com>
To:     Alan Douglas <adouglas@...ence.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "kishon@...com" <kishon@...com>,
        "niklas.cassel@...s.com" <niklas.cassel@...s.com>,
        "jesper.nilsson@...s.com" <jesper.nilsson@...s.com>
Cc:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 10/10] tools: PCI: Add MSI-X support

Hi Alan,

On 24/04/2018 10:57, Alan Douglas wrote:
> Hi Gustavo,
> 
> On 10 April 2018 18:15, Gustavo Pimentel wrote:
>> Adds MSI-X support to the pcitest tool and modified the pcitest.sh script to
>> accomodate this new type of interruption test.
>>
>> Signed-off-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
>> ---
>>  include/uapi/linux/pcitest.h |  1 +
>>  tools/pci/pcitest.c          | 18 +++++++++++++++++-
>>  tools/pci/pcitest.sh         | 25 +++++++++++++++++++++++++
>>  3 files changed, 43 insertions(+), 1 deletion(-)
> I found some possible problems when testing with the Cadence EP driver.  The problem
> is that pcitest uses the BARs for tests, but we also use one for the MSI-X tables
> 
> In Cadence core the MSI-X table is in BAR0 by default, but this is configured to a size
> of 0x80 in the test driver, since it is used as the test_reg_bar.  So, I changed the 
> configuration to use BAR4 instead, which is configured to a size of 131072 
> in pci-efp-test.c, and this gives me enough space.
> 
> However, if I run the BAR tests in pcitest before running the MSI-X tests, the
> MSI-X tests fail, since the BAR content is overwritten.  It's not a problem with the 
> scenario in pcitest.sh, but it would be if the module wasn't re-loaded.
> 
> So, wondering if we need to come up with some mechanism to specify that a specific
> BAR will be used for MSI-X, and that its size and content shouldn't be modified by
> pcitest?

I see your point. I have bypassed the problem by doing the module load/unload
(to avoid having to fight on multiple fronts).

I like your suggestion. Maybe we could have a bool variable for each BARs that
could be set to false if a resource have intent to use it.

However this change must be accepted by Kishon.

> 
> Regards,
> Alan
> 
Regards,
Gustavo