linux-kernel - Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support

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Date:	Mon, 5 Oct 2015 04:11:59 +0100
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Vlad Zolotarov <vladz@...udius-systems.com>
Cc:	linux-kernel@...r.kernel.org, mst@...hat.com, hjk@...sjkoch.de,
	corbet@....net, bruce.richardson@...el.com,
	avi@...udius-systems.com, gleb@...udius-systems.com,
	stephen@...workplumber.org, alexander.duyck@...il.com
Subject: Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support

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@...udius-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@...udius-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@...hat.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?

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.

greg k-h
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