Re: [PATCH v2 3/7] iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv_regions

[Lu Baolu]

Hi James,

On 3/14/19 7:58 PM, James Sewart wrote:

To support mapping ISA region via iommu_group_create_direct_mappings,
make sure its exposed by iommu_get_resv_regions. This allows
deduplication of reserved region mappings

Signed-off-by: James Sewart <jamessew...@arista.com>
---
  drivers/iommu/intel-iommu.c | 42 +++++++++++++++++++++++++++++--------
  1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 8e0a4e2ff77f..2e00e8708f06 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -337,6 +337,8 @@ static LIST_HEAD(dmar_rmrr_units);
  #define for_each_rmrr_units(rmrr) \
        list_for_each_entry(rmrr, &dmar_rmrr_units, list)

+static struct iommu_resv_region *isa_resv_region;

+
  /* bitmap for indexing intel_iommus */
  static int g_num_of_iommus;

@@ -2780,26 +2782,34 @@ static inline int iommu_prepare_rmrr_dev(struct dmar_rmrr_unit *rmrr,

                                          rmrr->end_address);
  }

+static inline struct iommu_resv_region *iommu_get_isa_resv_region(void)

+{
+       if (!isa_resv_region)
+               isa_resv_region = iommu_alloc_resv_region(0,
+                               16*1024*1024,
+                               0, IOMMU_RESV_DIRECT);
+
+       return isa_resv_region;
+}
+
  #ifdef CONFIG_INTEL_IOMMU_FLOPPY_WA
-static inline void iommu_prepare_isa(void)
+static inline void iommu_prepare_isa(struct pci_dev *pdev)
  {
-       struct pci_dev *pdev;
        int ret;
+       struct iommu_resv_region *reg = iommu_get_isa_resv_region();

- pdev = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, NULL);

-       if (!pdev)
+       if (!reg)
                return;

pr_info("Prepare 0-16MiB unity mapping for LPC\n");

-       ret = iommu_prepare_identity_map(&pdev->dev, 0, 16*1024*1024 - 1);
+       ret = iommu_prepare_identity_map(&pdev->dev, reg->start,
+                       reg->start + reg->length - 1);

if (ret)

                pr_err("Failed to create 0-16MiB identity map - floppy might not 
work\n");
-
-       pci_dev_put(pdev);
  }
  #else
-static inline void iommu_prepare_isa(void)
+static inline void iommu_prepare_isa(struct pci_dev *pdev)
  {
        return;
  }
@@ -3289,6 +3299,7 @@ static int __init init_dmars(void)
        struct dmar_rmrr_unit *rmrr;
        bool copied_tables = false;
        struct device *dev;
+       struct pci_dev *pdev;
        struct intel_iommu *iommu;
        int i, ret;

@@ -3469,7 +3480,11 @@ static int __init init_dmars(void)

                }
        }

- iommu_prepare_isa();

+       pdev = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, NULL);
+       if (pdev) {
+               iommu_prepare_isa(pdev);
+               pci_dev_put(pdev);
+       }

domains_done: @@ -5266,6 +5281,7 @@ static void intel_iommu_get_resv_regions(struct device *device,

        struct iommu_resv_region *reg;
        struct dmar_rmrr_unit *rmrr;
        struct device *i_dev;
+       struct pci_dev *pdev;
        int i;

rcu_read_lock();

@@ -5280,6 +5296,14 @@ static void intel_iommu_get_resv_regions(struct device 
*device,
        }
        rcu_read_unlock();

+ if (dev_is_pci(device)) {

+               pdev = to_pci_dev(device);
+               if ((pdev->class >> 8) == PCI_CLASS_BRIDGE_ISA) {
+                       reg = iommu_get_isa_resv_region();
+                       list_add_tail(&reg->list, head);
+               }
+       }
+

Just wondering why not just

+#ifdef CONFIG_INTEL_IOMMU_FLOPPY_WA
+       if (dev_is_pci(device)) {
+               pdev = to_pci_dev(device);
+               if ((pdev->class >> 8) == PCI_CLASS_BRIDGE_ISA) {
+                       reg = iommu_alloc_resv_region(0,
+                               16*1024*1024,
+                               0, IOMMU_RESV_DIRECT);
+                       if (reg)
+                               list_add_tail(&reg->list, head);
+               }
+       }
+#endif

and, remove all other related code?

Best regards,
Lu Baolu
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