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

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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@xxxxxxxxxx>
> > ---
> >   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;



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