Re: [PATCH v2 08/11] iommu/vt-d: Use pci_ats_supported() - Jean-Philippe Brucker

From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: bhelgaas@google.com, will@kernel.org, robh+dt@kernel.org,
	joro@8bytes.org, sudeep.holla@arm.com, linux-doc@vger.kernel.org,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	devicetree@vger.kernel.org, linux-acpi@vger.kernel.org,
	iommu@lists.linux-foundation.org, lorenzo.pieralisi@arm.com,
	corbet@lwn.net, mark.rutland@arm.com, liviu.dudau@arm.com,
	guohanjun@huawei.com, rjw@rjwysocki.net, lenb@kernel.org,
	robin.murphy@arm.com, dwmw2@infradead.org,
	amurray@thegoodpenguin.co.uk, frowand.list@gmail.com
Subject: Re: [PATCH v2 08/11] iommu/vt-d: Use pci_ats_supported()
Date: Thu, 12 Mar 2020 08:54:36 +0100	[thread overview]
Message-ID: <20200312075436.GA568802@myrica> (raw)
In-Reply-To: <7019230c-3c56-e6db-6704-d73f23fa39b5@linux.intel.com>

Hi Baolu,

On Thu, Mar 12, 2020 at 09:44:16AM +0800, Lu Baolu wrote:
> Hi Jean,
> 
> On 2020/3/11 20:45, Jean-Philippe Brucker wrote:
> > The pci_ats_supported() function checks if a device supports ATS and is
> > allowed to use it.
> > 
> > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > ---
> >   drivers/iommu/intel-iommu.c | 9 +++------
> >   1 file changed, 3 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> > index 6fa6de2b6ad5..17208280ef5c 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -1454,8 +1454,7 @@ static void iommu_enable_dev_iotlb(struct device_domain_info *info)
> >   	    !pci_reset_pri(pdev) && !pci_enable_pri(pdev, 32))
> >   		info->pri_enabled = 1;
> >   #endif
> > -	if (!pdev->untrusted && info->ats_supported &&
> > -	    pci_ats_page_aligned(pdev) &&
> > +	if (info->ats_supported && pci_ats_page_aligned(pdev) &&
> >   	    !pci_enable_ats(pdev, VTD_PAGE_SHIFT)) {
> >   		info->ats_enabled = 1;
> >   		domain_update_iotlb(info->domain);
> > @@ -2611,10 +2610,8 @@ static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
> >   	if (dev && dev_is_pci(dev)) {
> >   		struct pci_dev *pdev = to_pci_dev(info->dev);
> > -		if (!pdev->untrusted &&
> > -		    !pci_ats_disabled() &&
> 
> The pci_ats_disabled() couldn't be replaced by pci_ats_supported(). Even
> pci_ats_supported() returns true, user still can disable it. Or move
> ats_disabled into pci_ats_supported()?

It is already there, but hidden behind the "if (!dev->ats_cap)":
pci_ats_init() only sets dev->ats_cap after checking that
pci_ats_disabled() returns false.

Thanks,
Jean

> 
> Best regards,
> baolu
> 
> > -		    ecap_dev_iotlb_support(iommu->ecap) &&
> > -		    pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ATS) &&
> > +		if (ecap_dev_iotlb_support(iommu->ecap) &&
> > +		    pci_ats_supported(pdev) &&
> >   		    dmar_find_matched_atsr_unit(pdev))
> >   			info->ats_supported = 1;