linux-kernel - Re: [PATCH 1/1] iommu/vt-d: Fix incorrect cache invalidation for mm notification

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Date:   Mon, 20 Nov 2023 10:57:43 +1100
From:   Alistair Popple <apopple@...dia.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Kevin Tian <kevin.tian@...el.com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Huang Ying <ying.huang@...el.com>,
        Luo Yuzhang <yuzhang.luo@...el.com>,
        Tony Zhu <tony.zhu@...el.com>
Subject: Re: [PATCH 1/1] iommu/vt-d: Fix incorrect cache invalidation for mm
 notification


Lu Baolu <baolu.lu@...ux.intel.com> writes:

> Commit 6bbd42e2df8f ("mmu_notifiers: call invalidate_range() when
> invalidating TLBs") moved the secondary TLB invalidations into the TLB
> invalidation functions to ensure that all secondary TLB invalidations
> happen at the same time as the CPU invalidation and added a flush-all
> type of secondary TLB invalidation for the batched mode, where a range
> of [0, -1UL) is used to indicates that the range extends to the end of
> the address space.
>
> However, using an end address of -1UL caused an overflow in the Intel
> IOMMU driver, where the end address was rounded up to the next page.
> As a result, both the IOTLB and device ATC were not invalidated correctly.

Thanks for catching. This fix looks good so:

Reviewed-by: Alistair Popple <apopple@...dia.com>

However examining the fixes patch again I note that we are calling
mmu_notifier_invalidate_range(mm, 0, -1UL) from
arch_tlbbatch_add_pending() in arch/x86/include/asm/tlbflush.h.

That seems suboptimal because we would be doing an invalidate all for
every page unmap, and as of db6c1f6f236d ("mm/tlbbatch: introduce
arch_flush_tlb_batched_pending()") arch_flush_tlb_batched_pending()
calls flush_tlb_mm() anyway. So I think we can probably drop the
explicit notifier call from arch_flush_tlb_batched_pending().

Will put togeather a patch for that.

 - Alistair

> Add a flush all helper function and call it when the invalidation range
> is from 0 to -1UL, ensuring that the entire caches are invalidated
> correctly.
>
> Fixes: 6bbd42e2df8f ("mmu_notifiers: call invalidate_range() when invalidating TLBs")
> Cc: stable@...r.kernel.org
> Cc: Huang Ying <ying.huang@...el.com>
> Cc: Alistair Popple <apopple@...dia.com>
> Tested-by: Luo Yuzhang <yuzhang.luo@...el.com> # QAT
> Tested-by: Tony Zhu <tony.zhu@...el.com> # DSA
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/intel/svm.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
>
> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> index 50a481c895b8..588385050a07 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -216,6 +216,27 @@ static void intel_flush_svm_range(struct intel_svm *svm, unsigned long address,
>  	rcu_read_unlock();
>  }
>  
> +static void intel_flush_svm_all(struct intel_svm *svm)
> +{
> +	struct device_domain_info *info;
> +	struct intel_svm_dev *sdev;
> +
> +	rcu_read_lock();
> +	list_for_each_entry_rcu(sdev, &svm->devs, list) {
> +		info = dev_iommu_priv_get(sdev->dev);
> +
> +		qi_flush_piotlb(sdev->iommu, sdev->did, svm->pasid, 0, -1UL, 1);
> +		if (info->ats_enabled) {
> +			qi_flush_dev_iotlb_pasid(sdev->iommu, sdev->sid, info->pfsid,
> +						 svm->pasid, sdev->qdep,
> +						 0, 64 - VTD_PAGE_SHIFT);
> +			quirk_extra_dev_tlb_flush(info, 0, 64 - VTD_PAGE_SHIFT,
> +						  svm->pasid, sdev->qdep);
> +		}
> +	}
> +	rcu_read_unlock();
> +}
> +
>  /* Pages have been freed at this point */
>  static void intel_arch_invalidate_secondary_tlbs(struct mmu_notifier *mn,
>  					struct mm_struct *mm,
> @@ -223,6 +244,11 @@ static void intel_arch_invalidate_secondary_tlbs(struct mmu_notifier *mn,
>  {
>  	struct intel_svm *svm = container_of(mn, struct intel_svm, notifier);
>  
> +	if (start == 0 && end == -1UL) {
> +		intel_flush_svm_all(svm);
> +		return;
> +	}
> +
>  	intel_flush_svm_range(svm, start,
>  			      (end - start + PAGE_SIZE - 1) >> VTD_PAGE_SHIFT, 0);
>  }