netdev - Re: [PATCH] PCI: MSI: Remove unsafe and unnecessary hardware access

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Message-ID: <20100702161634.2529ad4e@virtuousgeek.org>
Date:	Fri, 2 Jul 2010 16:16:34 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Michael Chan <mchan@...adcom.com>, Matthew Wilcox <matthew@....cx>,
	linux-pci@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] PCI: MSI: Remove unsafe and unnecessary hardware access

On Thu, 17 Jun 2010 20:16:36 +0100
Ben Hutchings <bhutchings@...arflare.com> wrote:

> During suspend on an SMP system, {read,write}_msi_msg_desc() may be
> called to mask and unmask interrupts on a device that is already in a
> reduced power state.  At this point memory-mapped registers including
> MSI-X tables are not accessible, and config space may not be fully
> functional either.
> 
> While a device is in a reduced power state its interrupts are
> effectively masked and its MSI(-X) state will be restored when it is
> brought back to D0.  Therefore these functions can simply read and
> write msi_desc::msg for devices not in D0.
> 
> Further, read_msi_msg_desc() should only ever be used to update a
> previously written message, so it can always read msi_desc::msg
> and never needs to touch the hardware.
> 
> Signed-off-by: Ben Hutchings <bhutchings@...arflare.com>

Applied to my linux-next branch, thanks.

Matthew, let me know if you have an issue with this.

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center
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