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

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Message-ID: <4ff133f3-e541-4a0f-a72c-ce682720e6df@linux.intel.com>
Date: Thu, 15 Aug 2024 12:47:58 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: baolu.lu@...ux.intel.com, 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 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:

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