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SubjectRe: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support
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On 10/05/15 06:11, Greg KH wrote:
> On Sun, Oct 04, 2015 at 11:43:17PM +0300, Vlad Zolotarov wrote:
>> Add support for MSI and MSI-X interrupt modes:
>> - Interrupt mode selection order is:
>> INT#X (for backward compatibility) -> MSI-X -> MSI.
>> - Add ioctl() commands:
>> - UIO_PCI_GENERIC_INT_MODE_GET: query the current interrupt mode.
>> - UIO_PCI_GENERIC_IRQ_NUM_GET: query the maximum number of IRQs.
>> - UIO_PCI_GENERIC_IRQ_SET: bind the IRQ to eventfd (similar to vfio).
>> - Add mappings to all bars (memory and portio): some devices have
>> registers related to MSI/MSI-X handling outside BAR0.
>>
>> Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
>> ---
>> New in v3:
>> - Add __iomem qualifier to temp buffer receiving ioremap value.
>>
>> New in v2:
>> - Added #include <linux/uaccess.h> to uio_pci_generic.c
>>
>> Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
>> ---
>> drivers/uio/uio_pci_generic.c | 410 +++++++++++++++++++++++++++++++++++++---
>> include/linux/uio_pci_generic.h | 36 ++++
>> 2 files changed, 423 insertions(+), 23 deletions(-)
>> create mode 100644 include/linux/uio_pci_generic.h
>>
>> diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c
>> index d0b508b..6b8b1789 100644
>> --- a/drivers/uio/uio_pci_generic.c
>> +++ b/drivers/uio/uio_pci_generic.c
>> @@ -22,16 +22,32 @@
>> #include <linux/device.h>
>> #include <linux/module.h>
>> #include <linux/pci.h>
>> +#include <linux/msi.h>
>> #include <linux/slab.h>
>> #include <linux/uio_driver.h>
>> +#include <linux/uio_pci_generic.h>
>> +#include <linux/eventfd.h>
>> +#include <linux/uaccess.h>
>>
>> #define DRIVER_VERSION "0.01.0"
>> #define DRIVER_AUTHOR "Michael S. Tsirkin <mst@redhat.com>"
>> #define DRIVER_DESC "Generic UIO driver for PCI 2.3 devices"
>>
>> +struct msix_info {
>> + int num_irqs;
>> + struct msix_entry *table;
>> + struct uio_msix_irq_ctx {
>> + struct eventfd_ctx *trigger; /* MSI-x vector to eventfd */
> Why are you using eventfd for msi vectors? What's the reason for
> needing this?

A small correction - for MSI-X vectors. There may be only one MSI vector
per PCI function and if it's used it would use the same interface as a
legacy INT#x interrupt uses at the moment.
So, for MSI-X case the reason is that there may be (in most cases there
will be) more than one interrupt vector. Thus, as I've explained in a
PATCH1 thread we need a way to indicated each of them separately.
eventfd seems like a good way of doing so. If u have better ideas, pls.,
share.

>
> You haven't documented how this api works at all, you are going to have
> to a lot more work to justify this, as this greatly increases the
> complexity of the user/kernel api in unknown ways.

I actually do documented it a bit. Pls., check PATCH3 out. I admit that
I could do a better job by for instance providing a code example. I'll
improve this in v4 once we agree on all other details.

thanks,
vlad

>
> greg k-h



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