linux-kernel - Re: [RFC, v1 0/3] msi support for platform devices

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Message-ID: <96436cba-88e3-ddb6-36d6-000929b86979@redhat.com>
Date:   Thu, 12 Nov 2020 19:40:14 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Vikas Gupta <vikas.gupta@...adcom.com>, alex.williamson@...hat.com,
        cohuck@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     vikram.prakash@...adcom.com, srinath.mannam@...adcom.com
Subject: Re: [RFC, v1 0/3] msi support for platform devices

Hi Vikas,

On 11/12/20 6:58 PM, Vikas Gupta wrote:
> This RFC adds support for MSI for platform devices.
> a) MSI(s) is/are added in addition to the normal interrupts.
> b) The vendor specific MSI configuration can be done using
>    callbacks which is implemented as msi module.
> c) Adds a msi handling module for the Broadcom platform devices.
> 
> Changes from:
> -------------
>  v0 to v1:
>    i)  Removed MSI device flag VFIO_DEVICE_FLAGS_MSI.
>    ii) Add MSI(s) at the end of the irq list of platform IRQs.
>        MSI(s) with first entry of MSI block has count and flag
>        information.
>        IRQ list: Allocation for IRQs + MSIs are allocated as below
>        Example: if there are 'n' IRQs and 'k' MSIs
>        -------------------------------------------------------
>        |IRQ-0|IRQ-1|....|IRQ-n|MSI-0|MSI-1|MSI-2|......|MSI-k|
>        -------------------------------------------------------
I have not taken time yet to look at your series, but to me you should have
|IRQ-0|IRQ-1|....|IRQ-n|MSI|MSIX
then for setting a given MSIX (i) you would select the MSIx index and
then set start=i count=1.
to me individual MSIs are encoded in the subindex and not in the index.
The index just selects the "type" of interrupt.

For PCI you just have:
        VFIO_PCI_INTX_IRQ_INDEX,
        VFIO_PCI_MSI_IRQ_INDEX, -> MSI index and then you play with
start/count
        VFIO_PCI_MSIX_IRQ_INDEX,
        VFIO_PCI_ERR_IRQ_INDEX,
        VFIO_PCI_REQ_IRQ_INDEX,

(include/uapi/linux/vfio.h)

Thanks

Eric
>        MSI-0 will have count=k set and flags set accordingly.
> 
> Vikas Gupta (3):
>   vfio/platform: add support for msi
>   vfio/platform: change cleanup order
>   vfio/platform: add Broadcom msi module
> 
>  drivers/vfio/platform/Kconfig                 |   1 +
>  drivers/vfio/platform/Makefile                |   1 +
>  drivers/vfio/platform/msi/Kconfig             |   9 +
>  drivers/vfio/platform/msi/Makefile            |   2 +
>  .../vfio/platform/msi/vfio_platform_bcmplt.c  |  74 ++++++
>  drivers/vfio/platform/vfio_platform_common.c  |  86 ++++++-
>  drivers/vfio/platform/vfio_platform_irq.c     | 238 +++++++++++++++++-
>  drivers/vfio/platform/vfio_platform_private.h |  23 ++
>  8 files changed, 419 insertions(+), 15 deletions(-)
>  create mode 100644 drivers/vfio/platform/msi/Kconfig
>  create mode 100644 drivers/vfio/platform/msi/Makefile
>  create mode 100644 drivers/vfio/platform/msi/vfio_platform_bcmplt.c
>