linux-kernel - Re: [PATCH ACS v4 1/1] Enabling PCI ACS P2P upstream forwarding

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Message-ID: <20091006234208.GB23140@sequoia.sous-sol.org>
Date:	Tue, 6 Oct 2009 16:42:08 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Allen Kay <allen.m.kay@...el.com>
Cc:	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	jbarnes@...tuousgeek.org, matthew@....cx, chris@...s-sol.org,
	jeremy@...p.org
Subject: Re: [PATCH ACS v4 1/1] Enabling PCI ACS P2P upstream forwarding

* Allen Kay (allen.m.kay@...el.com) wrote:
> +#ifdef CONFIG_DMAR
> +extern int iommu_detected;
> +#endif

This should not be needed.

> +
> +#ifdef CONFIG_XEN
> +extern int xen_domain_type;
> +#endif

Nor this (there's already a check for is dom0 called xen_initial_domain(),
but unclear it's relevant yet for this patch).

> +
> +	/* Enable ACS P2P upstream forwarding if HW iommu is detected */
> +	if (iommu_detected)

I think you'd want iommu_found() instead.  To avoid, e.g., GART
triggering this one.

> +		pci_enable_acs(dev);
> +
> +#ifdef CONFIG_XEN
> +	/* HW iommu is not visible in xen dom0 */
> +	if (xen_domain_type)
> +		pci_enable_acs(dev);

could do this (xen_initial_domain()) above, but it's only relevant for
dom0 (so not needed yet?), and really seems to like it should be done by hv.

thanks,
-chris
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