linux-kernel - Re: [PATCH] PCI MSI: allow alignment restrictions on vector allocation

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Message-ID: <alpine.DEB.2.20.1710021817500.9529@nanos>
Date:   Mon, 2 Oct 2017 18:19:36 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Daniel Drake <drake@...lessm.com>
cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        x86@...nel.org, linux-wireless@...r.kernel.org,
        ath9k-devel@....qualcomm.com, linux@...lessm.com
Subject: Re: [PATCH] PCI MSI: allow alignment restrictions on vector
 allocation

On Mon, 2 Oct 2017, Thomas Gleixner wrote:
> On Mon, 2 Oct 2017, Daniel Drake wrote:
>   2) The affinity setting of straight MSI interrupts (w/o remapping) on x86
>      requires to make the affinity change from the interrupt context of the
>      current active vector in order not to lose interrupts or worst case
>      getting into a stale state.
> 
>      That works for single vectors, but trying to move all vectors in one
>      go is more or less impossible, as there is no reliable way to
>      determine that none of the other vectors is on flight.
> 
>      There might be some 'workarounds' for that, but I rather avoid that
>      unless we get an official documented one from Intel/AMD.

Thinking more about it. That might be actually a non issue for MSI, but we
have that modus operandi in the current code and we need to address that
first before even thinking about multi MSI support.

Thanks,

	tglx