On 2/13/19 12:26 AM, Tian, Kevin wrote:
From: iommu-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx [mailto:iommu-
bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx] On Behalf Of
sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx
Sent: Tuesday, February 12, 2019 5:51 AM
To: bhelgaas@xxxxxxxxxx; joro@xxxxxxxxxx; dwmw2@xxxxxxxxxxxxx
Cc: Raj, Ashok <ashok.raj@xxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx; linux-
kernel@xxxxxxxxxxxxxxx; Busch, Keith <keith.busch@xxxxxxxxx>;
iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; Pan, Jacob jun
<jacob.jun.pan@xxxxxxxxx>
Subject: [PATCH v2 2/2] iommu/vt-d: Enable PASID only if device expects
PASID in PRG Response.
From: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
In Intel IOMMU, if the Page Request Queue (PRQ) is full, it will
automatically respond to the device with a success message as a keep
alive. And when sending the success message, IOMMU will include PASID in
the Response Message when the Page Request has a PASID in Request
Message and It does not check against the PRG Response PASID
requirement
of the device before sending the response. Also, If the device receives the
PRG response with PASID when its not expecting it then the device behavior
is undefined. So enable PASID support only if device expects PASID in PRG
response message.
Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Suggested-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---
drivers/iommu/intel-iommu.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 1457f931218e..af2e4a011787 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1399,7 +1399,8 @@ static void iommu_enable_dev_iotlb(struct
device_domain_info *info)
undefined. So always enable PASID support on devices which
have it, even if we can't yet know if we're ever going to
use it. */
- if (info->pasid_supported && !pci_enable_pasid(pdev, info-
pasid_supported & ~1))
+ if (info->pasid_supported && pci_prg_resp_pasid_required(pdev)
&&
+ !pci_enable_pasid(pdev, info->pasid_supported & ~1))
info->pasid_enabled = 1;
Above logic looks problematic. As Dave commented in another thread,
PRI and PASID are orthogonal capabilities. Especially with introduction
of VT-d scalable mode, PASID will be used alone even w/o PRI...
Why not doing the check when PRI is actually enabled? At that point
you can fail the request if above condition is false.
yes, makes sense. I will fix it in next version.
if (info->pri_supported && !pci_reset_pri(pdev)
&& !pci_enable_pri(pdev, 32))
--
2.20.1
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--
Sathyanarayanan Kuppuswamy
Linux kernel developer
