Messages in this thread | | | From | "Tian, Kevin" <> | Subject | RE: [PATCH 1/1] iommu/vt-d: Omit devTLB invalidation requests when TES=0 | Date | Tue, 14 Nov 2023 05:31:20 +0000 |
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> From: Baolu Lu <baolu.lu@linux.intel.com> > Sent: Tuesday, November 14, 2023 12:55 PM > > 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. >
Okay.
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
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