Re: [Xen-devel] Loading PCIe Device Driver at Dom0

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, May 24, 2012 at 04:21:16PM -0700, Kenneth Wong wrote:
> Hi all,
> 
> I am now using dma_alloc_coherent().
> 
> However, the first parameter, pdev->dev required, which is "struct device", 
> does not seem to have initialized.  
> 
> When and who is suppose to initialize it?

Um, does your driver have a PCI vendor and model? It would
do it from the struct pci_driver->probe function.

> 
> In Linux, I can pass "NULL" and it just works.  In Xen, it crashes.  

NULL in that case is incorrect.
> 
> Sometimes insmod pass, sometimes hangs the system.
> 
> Please advise!

Look at how other drivers do it. You might also want to
pick up an Linux Device Drivers book and read the chapter
about PCI devices.

> 
> Kenneth
> ________________________________________
> From: Pasi Kärkkäinen [pasik@xxxxxx]
> Sent: Wednesday, May 23, 2012 11:18 PM
> To: Kenneth Wong
> Cc: xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Loading PCIe Device Driver at Dom0
> 
> On Wed, May 23, 2012 at 07:41:34PM -0700, Kenneth Wong wrote:
> > Hi Konrad and others,
> >
> > Oh, there are Xen/dom0 specific APIs for PCI and DMA?
> >
> 
> PCI/DMA APIs are the Linux kernel APIs, not Xen specific.
> 
> 
> > May I ask the names and where can I can more info on the APIs?
> >
> 
> Quick googling reveals:
> 
> http://www.mjmwired.net/kernel/Documentation/DMA-API.txt
> http://www.mjmwired.net/kernel/Documentation/DMA-API-HOWTO.txt
> 
> 
> -- Pasi
> 
> > Many thanks!
> >
> > Kenneth
> >
> > ________________________________________
> > From: Konrad Rzeszutek Wilk [konrad.wilk@xxxxxxxxxx]
> > Sent: Wednesday, May 23, 2012 5:17 PM
> > To: Kenneth Wong
> > Cc: xen-devel@xxxxxxxxxxxxx
> > Subject: Re: [Xen-devel] Loading PCIe Device Driver at Dom0
> >
> > On Wed, May 23, 2012 at 04:43:55PM -0700, Kenneth Wong wrote:
> > > Dear all,
> > >
> > > I have a PCIe device driver that I have been using on various Linux 
> > > distributions and Kernel versions (2.6.x - 3.x.y) successfully all along.
> > >
> > > I recently set up a Xen environment with Linux Mint 12 and Xen Hypervisor 
> > > 4.1.  When I boot to Linux Mint, my driver still load (via insmod 
> > > manually) successfully at Dom0 without any issue.  I can do reads and 
> > > write to the hardware device.  But once booted to Xen, the driver failed 
> > > to complete the driver load (via insmod manually) at Dom 0 and the 
> > > console just hangs.
> > >
> > > >From my debug messages, it appears it hangs because the driver doesn't 
> > > >receive any interrupt after a command is sent to the hardware device by 
> > > >writing a parameter to the mapped register.  Once that register is 
> > > >written, the device is expected to DMA the command from the buffer 
> > > >allocated by the driver.
> > >
> > > The things that I can only think of that might have caused the problem 
> > > are 1) IRQ mapping issue, or 2) DMA mapping issue, which I am not sure.
> >
> > The 2).
> > >
> > >
> > > What the driver does:
> >
> > You do need to use the PCI API (or the DMA API).
> >
> > >
> > > Set up a command buffer:
> > > Buf_t *buf = kmalloc(BUF_SIZE*sizeof(buf_t), GFP_KERNEL);
> > > unsigned long buf_addr = __pa(buf);
> > > unsigned int buf_addr_low = (unsigned int)buf_addr;
> > >
> > > Tell device about the buffer:
> > > iowrite32(buf_addr_low, dev->pci_reg_map + BUF_ADR__LOW);
> >
> > >
> > > Set up IRQ:
> > >     if (pci_find_capability(dev, PCI_CAP_ID_MSI) &&
> > >         (!pci_enable_msi(dev)))
> > >     {
> > >         if (request_irq(dev->irq, func_msi_interrupt, IRQF_SHARED, 
> > > DRIVER_NAME, my_dev))
> > >         {
> > >             return  -ENODEV;
> > >         }
> > >         my_dev->intr_mode = INTERRUPT_MSI;
> > >     }
> > >
> > > Ask device to fetch command from buffer (Expect interrupt after this 
> > > after device fetched the command from buf.  But interrupt did not 
> > > happen.):
> > > iowrite32(buf_offset, dev->pci_reg_map + FETCH_CMD_REG);
> > >
> > >
> > > >From dmesg, it looks like IRQ initialization is complete.
> > > [  241.743769] My_driver initialization
> > > [  241.743787] xen: registering gsi 16 triggering 0 polarity 1
> > > [  241.743793] xen_map_pirq_gsi: returning irq 16 for gsi 16
> > > [  241.743795] xen: --> pirq=16 -> irq=16 (gsi=16)
> > > [  241.743801] Already setup the GSI :16
> > > [  241.743805] my-driver 0000:02:00.0: PCI INT A -> GSI 16 (level, low) 
> > > -> IRQ 16
> > > [  241.743815] my-driver 0000:02:00.0: setting latency timer to 64
> > >
> > > /proc/interrupts:
> > >             CPU0       CPU1       CPU2       CPU3       CPU4       CPU5   
> > >     CPU6       CPU7
> > > ......
> > > ......
> > > 339:          0          0          0          0          0          0    
> > >       0          0  xen-pirq-msi       my-driver
> > > ......
> > > ......
> > >
> > > Any idea what might cause the problem?
> > >
> > > Is there anything we have to be enable/disable, use different functions, 
> > > or do differently in drivers written for Xen Dom0 environment regarding 
> > > the following?
> > > 1)       Allocating a DMA buffer in driver to allow the device to DMA 
> > > stuffs.
> > > 2)       Requesting MSI irq.
> > >
> > > Please advise!
> > >
> > > Thanks a lot in advance!!
> > >
> > > Kenneth
> >
> > > _______________________________________________
> > > Xen-devel mailing list
> > > Xen-devel@xxxxxxxxxxxxx
> > > http://lists.xen.org/xen-devel
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
> 
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