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

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Date:   Fri, 15 Mar 2019 10:19:05 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     James Sewart <jamessewart@...sta.com>,
        iommu@...ts.linux-foundation.org
Cc:     baolu.lu@...ux.intel.com, Tom Murphy <tmurphy@...sta.com>,
        Dmitry Safonov <dima@...sta.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/7] iommu/vt-d: Expose ISA direct mapping region via
 iommu_get_resv_regions

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 <jamessewart@...sta.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