linux-kernel - Re: [patch 21/32] NTB/msi: Convert to msi_on_each

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Date:   Wed, 01 Dec 2021 23:03:02 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dave Jiang <dave.jiang@...el.com>, Jason Gunthorpe <jgg@...dia.com>
Cc:     Logan Gunthorpe <logang@...tatee.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Marc Zygnier <maz@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Megha Dey <megha.dey@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, linux-pci@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jon Mason <jdmason@...zu.us>, Allen Hubbe <allenbh@...il.com>,
        linux-ntb@...glegroups.com, linux-s390@...r.kernel.org,
        Heiko Carstens <hca@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>, x86@...nel.org,
        Joerg Roedel <jroedel@...e.de>,
        iommu@...ts.linux-foundation.org
Subject: Re: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()

On Wed, Dec 01 2021 at 14:49, Dave Jiang wrote:
> On 12/1/2021 2:44 PM, Thomas Gleixner wrote:
>> How that is backed on the host does not really matter. You can expose
>> MSI-X to the guest with a INTx backing as well.
>>
>> I'm still failing to see the connection between the 9 MSIX vectors and
>> the 2048 IMS vectors which I assume that this is the limitation of the
>> physical device, right?
>
> I think I was confused with what you were asking and was thinking you 
> are saying why can't we just have MSIX on guest backed by the MSIX on 
> the physical device and thought there would not be enough vectors to 
> service the many guests. I think I understand what your position is now 
> with the clarification above.

This still depends on how this overall discussion about representation
of all of this stuff is resolved.

>> What needs a subdevice to expose?

Can you answer that too please?

Thanks,

        tglx