Messages in this thread | | | Date | Tue, 14 Nov 2023 12:54:46 +0800 | Subject | Re: [PATCH 1/1] iommu/vt-d: Omit devTLB invalidation requests when TES=0 | From | Baolu Lu <> |
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On 11/14/23 12:45 PM, Tian, Kevin wrote: >> From: Baolu Lu <baolu.lu@linux.intel.com> >> Sent: Tuesday, November 14, 2023 11:14 AM >> >> On 11/14/23 11:14 AM, Tian, Kevin wrote: >>>> From: Lu Baolu<baolu.lu@linux.intel.com> >>>> Sent: Tuesday, November 14, 2023 9:11 AM >>>> >>>> The latest VT-d spec indicates that when remapping hardware is disabled >>>> (TES=0 in Global Status Register), upstream ATS Invalidation Completion >>>> requests are treated as UR (Unsupported Request). >>>> >>>> Consequently, the spec recommends in section 4.3 Handling of Device-TLB >>>> Invalidations that software refrain from submitting any Device-TLB >>>> invalidation requests when address remapping hardware is disabled. >>>> >>>> Verify address remapping hardware is enabled prior to submitting Device- >>>> TLB invalidation requests. >>>> >>>> Fixes: 792fb43ce2c9 ("iommu/vt-d: Enable Intel IOMMU scalable mode by >>>> default") >>>> Signed-off-by: Lu Baolu<baolu.lu@linux.intel.com> >>>> --- >>>> drivers/iommu/intel/dmar.c | 18 ++++++++++++++++++ >>>> 1 file changed, 18 insertions(+) >>>> >>>> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c >>>> index a3414afe11b0..23cb80d62a9a 100644 >>>> --- a/drivers/iommu/intel/dmar.c >>>> +++ b/drivers/iommu/intel/dmar.c >>>> @@ -1522,6 +1522,15 @@ void qi_flush_dev_iotlb(struct intel_iommu >>>> *iommu, u16 sid, u16 pfsid, >>>> { >>>> struct qi_desc desc; >>>> >>>> + /* >>>> + * VT-d spec, section 4.3: >>>> + * >>>> + * Software is recommended to not submit any Device-TLB >>>> invalidation >>>> + * requests while address remapping hardware is disabled. >>>> + */ >>>> + if (!(iommu->gcmd & DMA_GCMD_TE)) >>>> + return; >>>> + >>> Is it a valid case to see such request when the iommu is disabled? >>> If not then let's add a WARN. >> >> There might be valid cases. The VT-d translation is turned on after all >> devices get probed. >> > > but I didn't get why there will be actual mapping changes before > vtd translation is enabled...
For an example, in iommu_create_device_direct_mappings(), iommu_flush_iotlb_all() is called after direct mappings are created.
Best regards, baolu
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