linux-kernel - Re: [RFC, v2 0/1] msi support for platform devices

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Message-ID: <014f8357-29ad-3e5a-9a34-0ee7cb9bf71c@redhat.com>
Date:   Wed, 2 Dec 2020 15:43:34 +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,
        ashwin.kamath@...adcom.com, zachary.schroff@...adcom.com,
        manish.kurup@...adcom.com
Subject: Re: [RFC, v2 0/1] msi support for platform devices

Hi Vikas,
On 11/24/20 5:16 PM, Vikas Gupta wrote:
> This RFC adds support for MSI for platform devices.
> MSI block is added as an ext irq along with the existing
> wired interrupt implementation.
> 
> Changes from:
> -------------
>  v1 to v2:
> 	1) IRQ allocation has been implemented as below:
> 	       ----------------------------
> 	       |IRQ-0|IRQ-1|....|IRQ-n|MSI|
>        	       ----------------------------
> 		MSI block has msi contexts and its implemneted
it is implemented
> 		as ext irq.
> 
> 	2) Removed vendor specific module for msi handling so
> 	   previously patch2 and patch3 are not required.
> 
> 	3) MSI related data is exported to userspace using 'caps'.
> 	 Please note VFIO_IRQ_INFO_CAP_TYPE in include/uapi/linux/vfio.h implementation
> 	is taken from the Eric`s patch
>         https://patchwork.kernel.org/project/kvm/patch/20201116110030.32335-8-eric.auger@redhat.com/
So do you mean that by exposing the vectors, now you do not need the msi
module anymore?


Thanks

Eric
> 
> 
>  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|
>        -------------------------------------------------------
>        MSI-0 will have count=k set and flags set accordingly.
> 
> Vikas Gupta (1):
>   vfio/platform: add support for msi
> 
>  drivers/vfio/platform/vfio_platform_common.c  |  99 ++++++-
>  drivers/vfio/platform/vfio_platform_irq.c     | 260 +++++++++++++++++-
>  drivers/vfio/platform/vfio_platform_private.h |  16 ++
>  include/uapi/linux/vfio.h                     |  43 +++
>  4 files changed, 401 insertions(+), 17 deletions(-)
>