Re: [PATCH v5 6/6] VT-d: support the device IOTLB

From: David Woodhouse <dwmw2@infradead.org>
To: Yu Zhao <yu.zhao@intel.com>
Cc: linux-pci@vger.kernel.org, iommu@lists.linux-foundation.org,
	kvm@vger.kernel.org, jbarnes@virtuousgeek.org
Subject: Re: [PATCH v5 6/6] VT-d: support the device IOTLB
Date: Sun, 09 Aug 2009 11:28:20 +0100	[thread overview]
Message-ID: <1249813700.4919.91.camel@macbook.infradead.org> (raw)
In-Reply-To: <1242625897-1678-7-git-send-email-yu.zhao@intel.com>

On Mon, 2009-05-18 at 13:51 +0800, Yu Zhao wrote:
> 
> +static struct device_domain_info *iommu_support_dev_iotlb(
> +       struct dmar_domain *domain, int segment, u8 bus, u8 devfn)
> +{
> +       int found = 0;
> +       unsigned long flags;
> +       struct device_domain_info *info;
> +       struct intel_iommu *iommu = device_to_iommu(segment, bus,
> devfn);
> +
> +       if (!ecap_dev_iotlb_support(iommu->ecap))
> +               return NULL;
> +
> +       if (!iommu->qi)
> +               return NULL;
> +
> +       spin_lock_irqsave(&device_domain_lock, flags);
> +       list_for_each_entry(info, &domain->devices, link)
> +               if (info->bus == bus && info->devfn == devfn) {
> +                       found = 1;
> +                       break;
> +               }
> +       spin_unlock_irqrestore(&device_domain_lock, flags);

What if there's more than one device? You only enable ATS for the first
device that supports it, and ignore the others?

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@intel.com                              Intel Corporation