Re: [PATCH] iommu/vt-d: Add a fix for devices need extra dtlb flush

[Jacob Pan]

Hi Ashok,

On Tue, 22 Nov 2022 16:52:26 +0000, Ashok Raj <ashok_raj@xxxxxxxxxxxxxxx>
wrote:

> On Mon, Nov 21, 2022 at 07:45:29PM -0800, Jacob Pan wrote:
> > QAT devices on Intel Sapphire Rapids and Emerald Rapids has a defect in
> >  
> 
> s/has/have
will do

> > address translation service (ATS). These devices may inadvertently issue
> > ATS invalidation completion before posted writes initiated with
> > translated address that utilized translations matching the invalidation
> > address range, violating the invalidation completion ordering.  
> 
> Above is a bit hard to read, can you see if the rephrasing works?
> 
> These devices send the invalidation response ahead of servicing any posted
> writes that could be using the same address range. This can lead to memory
> corruption.
> 
It is a little long but these are taken from the errata draft. I think it is
better to keep the wording consistent?

> > 
> > An additional device TLB invalidation is needed to ensure no more posted
> > writes with translated address following the invalidation completion.
> > 
> > Without this fix, DMA writes with translated address can happen after
> > device TLB invalidation is completed. Random data corruption can occur
> > as the DMA buffer gets reused after invalidation.  
> 
> Maybe drop both para above and replace with.
> 
> An additional dTLB invalidation ensures the ordering is preserved and
> prevents any data-corruption.
I can add this but I am not seeing any gains here.

> > 
> > This patch adds a flag to mark the need for an extra flush based on
> > given device IDs, this flag is set during initialization when ATS
> > support is enabled.
> > 
> > At runtime, this flag is used to control the extra dTLB flush. The
> > overhead of checking this unlikely true flag is smaller than checking
> > PCI device IDs every time.  
> 
> The above 2 para's can be dropped? Since that's what the code does and
> probably not needed in the commit log.
sounds good.

> > 
> > Device TLBs are invalidated under the following six conditions:
> > 1. Device driver does DMA API unmap IOVA
> > 2. Device driver unbind a PASID from a process, sva_unbind_device()
> > 3. PASID is torn down, after PASID cache is flushed. e.g. process
> > exit_mmap() due to crash
> > 4. Under SVA usage, called by mmu_notifier.invalidate_range() where
> > VM has to free pages that were unmapped
> > 5. userspace driver unmaps a DMA buffer
> > 6. Cache invalidation in vSVA usage (upcoming)
> > 
> > For #1 and #2, device drivers are responsible for stopping DMA traffic
> > before unmap/unbind. For #3, iommu driver gets mmu_notifier to
> > invalidate TLB the same way as normal user unmap which will do an extra
> > invalidation. The dTLB invalidation after PASID cache flush does not
> > need an extra invalidation.
> > 
> > Therefore, we only need to deal with #4 and #5 in this patch. #1 is also
> > covered by this patch due to common code path with #5.  
> 
> I was told to add an imperative statement to tell what the patch does,
> without the code. 
> 
> Maybe something like:
> 
> Add an extra device TLB invalidation for affected devices.
> 
Sounds good,I will merge this with the statement above.

> > 
> > Tested-by: Yuzhang Luo <yuzhang.luo@xxxxxxxxx>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > ---  
> 
> Reviewed-by: Ashok Raj <ashok.raj@xxxxxxxxx>
> 
> >  drivers/iommu/intel/iommu.c | 100 +++++++++++++++++++++++++++++-------
> >  drivers/iommu/intel/iommu.h |   3 ++
> >  drivers/iommu/intel/svm.c   |   4 +-
> >  3 files changed, 87 insertions(+), 20 deletions(-)
> > 
> > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> > index 996a8b5ee5ee..6254788330b8 100644
> > --- a/drivers/iommu/intel/iommu.c
> > +++ b/drivers/iommu/intel/iommu.c
> > @@ -1396,6 +1396,39 @@ static void domain_update_iotlb(struct
> > dmar_domain *domain) spin_unlock_irqrestore(&domain->lock, flags);
> >  }
> >  
> > +/*
> > + * Check that the device does not live on an external facing PCI port
> > that is
> > + * marked as untrusted. Such devices should not be able to apply
> > quirks and
> > + * thus not be able to bypass the IOMMU restrictions.
> > + */
> > +static bool risky_device(struct pci_dev *pdev)
> > +{
> > +	if (pdev->untrusted) {
> > +		pci_info(pdev,
> > +			 "Skipping IOMMU quirk for dev [%04X:%04X] on
> > untrusted PCI link\n",
> > +			 pdev->vendor, pdev->device);
> > +		pci_info(pdev, "Please check with your BIOS/Platform
> > vendor about this\n");
> > +		return true;
> > +	}
> > +	return false;
> > +}
> > +
> > +/* Impacted QAT device IDs ranging from 0x4940 to 0x4943 */
> > +#define BUGGY_QAT_DEVID_MASK 0x494c
> > +static bool dev_needs_extra_dtlb_flush(struct pci_dev *pdev)
> > +{
> > +	if (pdev->vendor != PCI_VENDOR_ID_INTEL)
> > +		return false;
> > +
> > +	if ((pdev->device & 0xfffc) != BUGGY_QAT_DEVID_MASK)
> > +		return false;
> > +
> > +	if (risky_device(pdev))
> > +		return false;
> > +
> > +	return true;
> > +}
> > +
> >  static void iommu_enable_pci_caps(struct device_domain_info *info)
> >  {
> >  	struct pci_dev *pdev;
> > @@ -1478,6 +1511,7 @@ static void __iommu_flush_dev_iotlb(struct
> > device_domain_info *info, qdep = info->ats_qdep;
> >  	qi_flush_dev_iotlb(info->iommu, sid, info->pfsid,
> >  			   qdep, addr, mask);
> > +	quirk_dev_tlb(info, addr, mask, PASID_RID2PASID, qdep);
> >  }
> >  
> >  static void iommu_flush_dev_iotlb(struct dmar_domain *domain,
> > @@ -4490,9 +4524,10 @@ static struct iommu_device
> > *intel_iommu_probe_device(struct device *dev) if (dev_is_pci(dev)) {
> >  		if (ecap_dev_iotlb_support(iommu->ecap) &&
> >  		    pci_ats_supported(pdev) &&
> > -		    dmar_ats_supported(pdev, iommu))
> > +		    dmar_ats_supported(pdev, iommu)) {
> >  			info->ats_supported = 1;
> > -
> > +			info->dtlb_extra_inval =
> > dev_needs_extra_dtlb_flush(pdev);
> > +		}
> >  		if (sm_supported(iommu)) {
> >  			if (pasid_supported(iommu)) {
> >  				int features =
> > pci_pasid_features(pdev); @@ -4680,23 +4715,6 @@ static bool
> > intel_iommu_is_attach_deferred(struct device *dev) return
> > translation_pre_enabled(info->iommu) && !info->domain; }
> >  
> > -/*
> > - * Check that the device does not live on an external facing PCI port
> > that is
> > - * marked as untrusted. Such devices should not be able to apply
> > quirks and
> > - * thus not be able to bypass the IOMMU restrictions.
> > - */
> > -static bool risky_device(struct pci_dev *pdev)
> > -{
> > -	if (pdev->untrusted) {
> > -		pci_info(pdev,
> > -			 "Skipping IOMMU quirk for dev [%04X:%04X] on
> > untrusted PCI link\n",
> > -			 pdev->vendor, pdev->device);
> > -		pci_info(pdev, "Please check with your BIOS/Platform
> > vendor about this\n");
> > -		return true;
> > -	}
> > -	return false;
> > -}
> > -
> >  static void intel_iommu_iotlb_sync_map(struct iommu_domain *domain,
> >  				       unsigned long iova, size_t size)
> >  {
> > @@ -4931,3 +4949,47 @@ static void __init check_tylersburg_isoch(void)
> >  	pr_warn("Recommended TLB entries for ISOCH unit is 16; your
> > BIOS set %d\n", vtisochctrl);
> >  }
> > +
> > +/*
> > + * Here we deal with a device TLB defect where device may
> > inadvertently issue ATS
> > + * invalidation completion before posted writes initiated with
> > translated address
> > + * that utilized translations matching the invalidation address range,
> > violating
> > + * the invalidation completion ordering.
> > + * Therefore, any use cases that cannot guarantee DMA is stopped
> > before unmap is
> > + * vulnerable to this defect. In other words, any dTLB invalidation
> > initiated not
> > + * under the control of the trusted/privileged host device driver must
> > use this
> > + * quirk.
> > + * Device TLBs are invalidated under the following six conditions:
> > + * 1. Device driver does DMA API unmap IOVA
> > + * 2. Device driver unbind a PASID from a process, sva_unbind_device()
> > + * 3. PASID is torn down, after PASID cache is flushed. e.g. process
> > + *    exit_mmap() due to crash
> > + * 4. Under SVA usage, called by mmu_notifier.invalidate_range() where
> > + *    VM has to free pages that were unmapped
> > + * 5. Userspace driver unmaps a DMA buffer
> > + * 6. Cache invalidation in vSVA usage (upcoming)
> > + *
> > + * For #1 and #2, device drivers are responsible for stopping DMA
> > traffic
> > + * before unmap/unbind. For #3, iommu driver gets mmu_notifier to
> > + * invalidate TLB the same way as normal user unmap which will use
> > this quirk.
> > + * The dTLB invalidation after PASID cache flush does not need this
> > quirk.
> > + *
> > + * As a reminder, #6 will *NEED* this quirk as we enable nested
> > translation.
> > + */
> > +void quirk_dev_tlb(struct device_domain_info *info, unsigned long
> > address,
> > +		   unsigned long mask, u32 pasid, u16 qdep)
> > +{
> > +	u16 sid;
> > +
> > +	if (likely(!info->dtlb_extra_inval))
> > +		return;
> > +
> > +	sid = PCI_DEVID(info->bus, info->devfn);
> > +	if (pasid == PASID_RID2PASID) {
> > +		qi_flush_dev_iotlb(info->iommu, sid, info->pfsid,
> > +				   qdep, address, mask);
> > +	} else {
> > +		qi_flush_dev_iotlb_pasid(info->iommu, sid, info->pfsid,
> > +					 pasid, qdep, address, mask);
> > +	}
> > +}
> > diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
> > index 92023dff9513..09b989bf545f 100644
> > --- a/drivers/iommu/intel/iommu.h
> > +++ b/drivers/iommu/intel/iommu.h
> > @@ -623,6 +623,7 @@ struct device_domain_info {
> >  	u8 pri_enabled:1;
> >  	u8 ats_supported:1;
> >  	u8 ats_enabled:1;
> > +	u8 dtlb_extra_inval:1;	/* Quirk for devices need extra
> > flush */ u8 ats_qdep;
> >  	struct device *dev; /* it's NULL for PCIe-to-PCI bridge */
> >  	struct intel_iommu *iommu; /* IOMMU used by this device */
> > @@ -728,6 +729,8 @@ void qi_flush_piotlb(struct intel_iommu *iommu, u16
> > did, u32 pasid, u64 addr, void qi_flush_dev_iotlb_pasid(struct
> > intel_iommu *iommu, u16 sid, u16 pfsid, u32 pasid, u16 qdep, u64 addr,
> >  			      unsigned int size_order);
> > +void quirk_dev_tlb(struct device_domain_info *info, unsigned long
> > address,
> > +		   unsigned long pages, u32 pasid, u16 qdep);
> >  void qi_flush_pasid_cache(struct intel_iommu *iommu, u16 did, u64
> > granu, u32 pasid);
> >  
> > diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> > index 7d08eb034f2d..117430b97ba9 100644
> > --- a/drivers/iommu/intel/svm.c
> > +++ b/drivers/iommu/intel/svm.c
> > @@ -184,10 +184,12 @@ static void __flush_svm_range_dev(struct
> > intel_svm *svm, return;
> >  
> >  	qi_flush_piotlb(sdev->iommu, sdev->did, svm->pasid, address,
> > pages, ih);
> > -	if (info->ats_enabled)
> > +	if (info->ats_enabled) {
> >  		qi_flush_dev_iotlb_pasid(sdev->iommu, sdev->sid,
> > info->pfsid, svm->pasid, sdev->qdep, address,
> >  					 order_base_2(pages));
> > +		quirk_dev_tlb(info, address, order_base_2(pages),
> > svm->pasid, sdev->qdep);
> > +	}
> >  }
> >  
> >  static void intel_flush_svm_range_dev(struct intel_svm *svm,
> > -- 
> > 2.25.1
> > 
> >   


Thanks,

Jacob