linux-kernel - Re: [PATCH 6/7] iommu/vt-d: Add helper to flush caches for context change

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Message-ID: <20240815063430.70ac9b00.alex.williamson@redhat.com>
Date: Thu, 15 Aug 2024 06:34:30 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, Jacob Pan
 <jacob.jun.pan@...ux.intel.com>, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] iommu/vt-d: Add helper to flush caches for context
 change

On Thu, 15 Aug 2024 12:47:58 +0800
Baolu Lu <baolu.lu@...ux.intel.com> wrote:

> On 2024/8/15 6:27, Alex Williamson wrote:
> > Hi Baolu,  
> 
> Hi Alex,
> 
> > This appears to be non-functional and breaks device assignment...  
> 
> Yes. This is broken. Thanks for pointing it out.
> 
> Perhaps I can fix it by passing domain id to the helper? Something like
> below:

Hi Baolu,

Yes, I did a similar quick fix to prove this was the issue.  Thanks,

Alex

> diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
> index 01002ae2a091..b3b295e60626 100644
> --- a/drivers/iommu/intel/iommu.h
> +++ b/drivers/iommu/intel/iommu.h
> @@ -1152,7 +1152,7 @@ void cache_tag_flush_range_np(struct dmar_domain 
> *domain, unsigned long start,
> 
>   void intel_context_flush_present(struct device_domain_info *info,
>   				 struct context_entry *context,
> -				 bool affect_domains);
> +				 u16 did, bool affect_domains);
> 
>   #ifdef CONFIG_INTEL_IOMMU_SVM
>   void intel_svm_check(struct intel_iommu *iommu);
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 159da629349c..34006b6e89eb 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1903,6 +1903,7 @@ static void domain_context_clear_one(struct 
> device_domain_info *info, u8 bus, u8
>   {
>   	struct intel_iommu *iommu = info->iommu;
>   	struct context_entry *context;
> +	u16 did;
> 
>   	spin_lock(&iommu->lock);
>   	context = iommu_context_addr(iommu, bus, devfn, 0);
> @@ -1911,10 +1912,11 @@ static void domain_context_clear_one(struct 
> device_domain_info *info, u8 bus, u8
>   		return;
>   	}
> 
> +	did = context_domain_id(context);
>   	context_clear_entry(context);
>   	__iommu_flush_cache(iommu, context, sizeof(*context));
>   	spin_unlock(&iommu->lock);
> -	intel_context_flush_present(info, context, true);
> +	intel_context_flush_present(info, context, did, true);
>   }
> 
>   static int domain_setup_first_level(struct intel_iommu *iommu,
> @@ -4077,6 +4079,7 @@ static int context_flip_pri(struct 
> device_domain_info *info, bool enable)
>   	struct intel_iommu *iommu = info->iommu;
>   	u8 bus = info->bus, devfn = info->devfn;
>   	struct context_entry *context;
> +	u16 did;
> 
>   	spin_lock(&iommu->lock);
>   	if (context_copied(iommu, bus, devfn)) {
> @@ -4089,6 +4092,7 @@ static int context_flip_pri(struct 
> device_domain_info *info, bool enable)
>   		spin_unlock(&iommu->lock);
>   		return -ENODEV;
>   	}
> +	did = context_domain_id(context);
> 
>   	if (enable)
>   		context_set_sm_pre(context);
> @@ -4097,7 +4101,7 @@ static int context_flip_pri(struct 
> device_domain_info *info, bool enable)
> 
>   	if (!ecap_coherent(iommu->ecap))
>   		clflush_cache_range(context, sizeof(*context));
> -	intel_context_flush_present(info, context, true);
> +	intel_context_flush_present(info, context, did, true);
>   	spin_unlock(&iommu->lock);
> 
>   	return 0;
> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
> index 5792c817cefa..b51fc268dc84 100644
> --- a/drivers/iommu/intel/pasid.c
> +++ b/drivers/iommu/intel/pasid.c
> @@ -683,6 +683,7 @@ static void device_pasid_table_teardown(struct 
> device *dev, u8 bus, u8 devfn)
>   	struct device_domain_info *info = dev_iommu_priv_get(dev);
>   	struct intel_iommu *iommu = info->iommu;
>   	struct context_entry *context;
> +	u16 did;
> 
>   	spin_lock(&iommu->lock);
>   	context = iommu_context_addr(iommu, bus, devfn, false);
> @@ -691,10 +692,11 @@ static void device_pasid_table_teardown(struct 
> device *dev, u8 bus, u8 devfn)
>   		return;
>   	}
> 
> +	did = context_domain_id(context);
>   	context_clear_entry(context);
>   	__iommu_flush_cache(iommu, context, sizeof(*context));
>   	spin_unlock(&iommu->lock);
> -	intel_context_flush_present(info, context, false);
> +	intel_context_flush_present(info, context, did, false);
>   }
> 
>   static int pci_pasid_table_teardown(struct pci_dev *pdev, u16 alias, 
> void *data)
> @@ -885,10 +887,9 @@ static void __context_flush_dev_iotlb(struct 
> device_domain_info *info)
>    */
>   void intel_context_flush_present(struct device_domain_info *info,
>   				 struct context_entry *context,
> -				 bool flush_domains)
> +				 u16 did, bool flush_domains)
>   {
>   	struct intel_iommu *iommu = info->iommu;
> -	u16 did = context_domain_id(context);
>   	struct pasid_entry *pte;
>   	int i;
> 
> Thanks,
> baolu
>