Re: [PATCH v3 01/12] iommu: Introduce dirty log tracking framework

[Lu Baolu <baolu.lu@linux.intel.com>]

Hi Keqian,

On 4/13/21 4:54 PM, Keqian Zhu wrote:
> Some types of IOMMU are capable of tracking DMA dirty log, such as
> ARM SMMU with HTTU or Intel IOMMU with SLADE. This introduces the
> dirty log tracking framework in the IOMMU base layer.
> 
> Three new essential interfaces are added, and we maintaince the status
> of dirty log tracking in iommu_domain.
> 1. iommu_switch_dirty_log: Perform actions to start|stop dirty log tracking
> 2. iommu_sync_dirty_log: Sync dirty log from IOMMU into a dirty bitmap
> 3. iommu_clear_dirty_log: Clear dirty log of IOMMU by a mask bitmap
> 
> A new dev feature are added to indicate whether a specific type of
> iommu hardware supports and its driver realizes them.
> 
> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
> ---
>   drivers/iommu/iommu.c | 150 ++++++++++++++++++++++++++++++++++++++++++
>   include/linux/iommu.h |  53 +++++++++++++++
>   2 files changed, 203 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index d0b0a15dba84..667b2d6d2fc0 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1922,6 +1922,7 @@ static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
>   	domain->type = type;
>   	/* Assume all sizes by default; the driver may override this later */
>   	domain->pgsize_bitmap  = bus->iommu_ops->pgsize_bitmap;
> +	mutex_init(&domain->switch_log_lock);
>   
>   	return domain;
>   }
> @@ -2720,6 +2721,155 @@ int iommu_domain_set_attr(struct iommu_domain *domain,
>   }
>   EXPORT_SYMBOL_GPL(iommu_domain_set_attr);
>   
> +int iommu_switch_dirty_log(struct iommu_domain *domain, bool enable,
> +			   unsigned long iova, size_t size, int prot)
> +{
> +	const struct iommu_ops *ops = domain->ops;
> +	int ret;
> +
> +	if (unlikely(!ops || !ops->switch_dirty_log))
> +		return -ENODEV;
> +
> +	mutex_lock(&domain->switch_log_lock);
> +	if (enable && domain->dirty_log_tracking) {
> +		ret = -EBUSY;
> +		goto out;
> +	} else if (!enable && !domain->dirty_log_tracking) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	ret = ops->switch_dirty_log(domain, enable, iova, size, prot);
> +	if (ret)
> +		goto out;
> +
> +	domain->dirty_log_tracking = enable;
> +out:
> +	mutex_unlock(&domain->switch_log_lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_switch_dirty_log);

Since you also added IOMMU_DEV_FEAT_HWDBM, I am wondering what's the
difference between

iommu_switch_dirty_log(on) vs. 
iommu_dev_enable_feature(IOMMU_DEV_FEAT_HWDBM)

iommu_switch_dirty_log(off) vs. 
iommu_dev_disable_feature(IOMMU_DEV_FEAT_HWDBM)

> +
> +int iommu_sync_dirty_log(struct iommu_domain *domain, unsigned long iova,
> +			 size_t size, unsigned long *bitmap,
> +			 unsigned long base_iova, unsigned long bitmap_pgshift)
> +{
> +	const struct iommu_ops *ops = domain->ops;
> +	unsigned int min_pagesz;
> +	size_t pgsize;
> +	int ret = 0;
> +
> +	if (unlikely(!ops || !ops->sync_dirty_log))
> +		return -ENODEV;
> +
> +	min_pagesz = 1 << __ffs(domain->pgsize_bitmap);
> +	if (!IS_ALIGNED(iova | size, min_pagesz)) {
> +		pr_err("unaligned: iova 0x%lx size 0x%zx min_pagesz 0x%x\n",
> +		       iova, size, min_pagesz);
> +		return -EINVAL;
> +	}
> +
> +	mutex_lock(&domain->switch_log_lock);
> +	if (!domain->dirty_log_tracking) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	while (size) {
> +		pgsize = iommu_pgsize(domain, iova, size);
> +
> +		ret = ops->sync_dirty_log(domain, iova, pgsize,
> +					  bitmap, base_iova, bitmap_pgshift);

Any reason why do you want to do this in a per-4K page manner? This can
lead to a lot of indirect calls and bad performance.

How about a sync_dirty_pages()?

The same comment applies to other places in this patch series.

> +		if (ret)
> +			break;
> +
> +		pr_debug("dirty_log_sync handle: iova 0x%lx pagesz 0x%zx\n",
> +			 iova, pgsize);
> +
> +		iova += pgsize;
> +		size -= pgsize;
> +	}
> +out:
> +	mutex_unlock(&domain->switch_log_lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sync_dirty_log);
> +
> +static int __iommu_clear_dirty_log(struct iommu_domain *domain,
> +				   unsigned long iova, size_t size,
> +				   unsigned long *bitmap,
> +				   unsigned long base_iova,
> +				   unsigned long bitmap_pgshift)
> +{
> +	const struct iommu_ops *ops = domain->ops;
> +	size_t pgsize;
> +	int ret = 0;
> +
> +	if (unlikely(!ops || !ops->clear_dirty_log))
> +		return -ENODEV;
> +
> +	while (size) {
> +		pgsize = iommu_pgsize(domain, iova, size);
> +
> +		ret = ops->clear_dirty_log(domain, iova, pgsize, bitmap,
> +					   base_iova, bitmap_pgshift);
> +		if (ret)
> +			break;
> +
> +		pr_debug("dirty_log_clear handled: iova 0x%lx pagesz 0x%zx\n",
> +			 iova, pgsize);
> +
> +		iova += pgsize;
> +		size -= pgsize;
> +	}
> +
> +	return ret;
> +}
> +
> +int iommu_clear_dirty_log(struct iommu_domain *domain,
> +			  unsigned long iova, size_t size,
> +			  unsigned long *bitmap, unsigned long base_iova,
> +			  unsigned long bitmap_pgshift)
> +{
> +	unsigned long riova, rsize;
> +	unsigned int min_pagesz;
> +	bool flush = false;
> +	int rs, re, start, end;
> +	int ret = 0;
> +
> +	min_pagesz = 1 << __ffs(domain->pgsize_bitmap);
> +	if (!IS_ALIGNED(iova | size, min_pagesz)) {
> +		pr_err("unaligned: iova 0x%lx min_pagesz 0x%x\n",
> +		       iova, min_pagesz);
> +		return -EINVAL;
> +	}
> +
> +	mutex_lock(&domain->switch_log_lock);
> +	if (!domain->dirty_log_tracking) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	start = (iova - base_iova) >> bitmap_pgshift;
> +	end = start + (size >> bitmap_pgshift);
> +	bitmap_for_each_set_region(bitmap, rs, re, start, end) {
> +		flush = true;
> +		riova = iova + (rs << bitmap_pgshift);
> +		rsize = (re - rs) << bitmap_pgshift;
> +		ret = __iommu_clear_dirty_log(domain, riova, rsize, bitmap,
> +					      base_iova, bitmap_pgshift);
> +		if (ret)
> +			break;
> +	}
> +
> +	if (flush)
> +		iommu_flush_iotlb_all(domain);
> +out:
> +	mutex_unlock(&domain->switch_log_lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_clear_dirty_log);
> +
>   void iommu_get_resv_regions(struct device *dev, struct list_head *list)
>   {
>   	const struct iommu_ops *ops = dev->bus->iommu_ops;
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 5e7fe519430a..7f9ed9f520e2 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -87,6 +87,8 @@ struct iommu_domain {
>   	void *handler_token;
>   	struct iommu_domain_geometry geometry;
>   	void *iova_cookie;
> +	bool dirty_log_tracking;
> +	struct mutex switch_log_lock;
>   };
>   
>   enum iommu_cap {
> @@ -160,6 +162,7 @@ struct iommu_resv_region {
>   enum iommu_dev_features {
>   	IOMMU_DEV_FEAT_AUX,	/* Aux-domain feature */
>   	IOMMU_DEV_FEAT_SVA,	/* Shared Virtual Addresses */
> +	IOMMU_DEV_FEAT_HWDBM,	/* Hardware Dirty Bit Management */
>   };
>   
>   #define IOMMU_PASID_INVALID	(-1U)
> @@ -205,6 +208,9 @@ struct iommu_iotlb_gather {
>    * @device_group: find iommu group for a particular device
>    * @domain_get_attr: Query domain attributes
>    * @domain_set_attr: Change domain attributes
> + * @switch_dirty_log: Perform actions to start|stop dirty log tracking
> + * @sync_dirty_log: Sync dirty log from IOMMU into a dirty bitmap
> + * @clear_dirty_log: Clear dirty log of IOMMU by a mask bitmap
>    * @get_resv_regions: Request list of reserved regions for a device
>    * @put_resv_regions: Free list of reserved regions for a device
>    * @apply_resv_region: Temporary helper call-back for iova reserved ranges
> @@ -260,6 +266,18 @@ struct iommu_ops {
>   	int (*domain_set_attr)(struct iommu_domain *domain,
>   			       enum iommu_attr attr, void *data);
>   
> +	/* Track dirty log */
> +	int (*switch_dirty_log)(struct iommu_domain *domain, bool enable,
> +				unsigned long iova, size_t size, int prot);
> +	int (*sync_dirty_log)(struct iommu_domain *domain,
> +			      unsigned long iova, size_t size,
> +			      unsigned long *bitmap, unsigned long base_iova,
> +			      unsigned long bitmap_pgshift);
> +	int (*clear_dirty_log)(struct iommu_domain *domain,
> +			       unsigned long iova, size_t size,
> +			       unsigned long *bitmap, unsigned long base_iova,
> +			       unsigned long bitmap_pgshift);
> +
>   	/* Request/Free a list of reserved regions for a device */
>   	void (*get_resv_regions)(struct device *dev, struct list_head *list);
>   	void (*put_resv_regions)(struct device *dev, struct list_head *list);
> @@ -511,6 +529,16 @@ extern int iommu_domain_get_attr(struct iommu_domain *domain, enum iommu_attr,
>   				 void *data);
>   extern int iommu_domain_set_attr(struct iommu_domain *domain, enum iommu_attr,
>   				 void *data);
> +extern int iommu_switch_dirty_log(struct iommu_domain *domain, bool enable,
> +				  unsigned long iova, size_t size, int prot);
> +extern int iommu_sync_dirty_log(struct iommu_domain *domain, unsigned long iova,
> +				size_t size, unsigned long *bitmap,
> +				unsigned long base_iova,
> +				unsigned long bitmap_pgshift);
> +extern int iommu_clear_dirty_log(struct iommu_domain *domain, unsigned long iova,
> +				 size_t dma_size, unsigned long *bitmap,
> +				 unsigned long base_iova,
> +				 unsigned long bitmap_pgshift);
>   
>   /* Window handling function prototypes */
>   extern int iommu_domain_window_enable(struct iommu_domain *domain, u32 wnd_nr,
> @@ -901,6 +929,31 @@ static inline int iommu_domain_set_attr(struct iommu_domain *domain,
>   	return -EINVAL;
>   }
>   
> +static inline int iommu_switch_dirty_log(struct iommu_domain *domain,
> +					 bool enable, unsigned long iova,
> +					 size_t size, int prot)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int iommu_sync_dirty_log(struct iommu_domain *domain,
> +				       unsigned long iova, size_t size,
> +				       unsigned long *bitmap,
> +				       unsigned long base_iova,
> +				       unsigned long pgshift)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int iommu_clear_dirty_log(struct iommu_domain *domain,
> +					unsigned long iova, size_t size,
> +					unsigned long *bitmap,
> +					unsigned long base_iova,
> +					unsigned long pgshift)
> +{
> +	return -EINVAL;
> +}
> +
>   static inline int  iommu_device_register(struct iommu_device *iommu)
>   {
>   	return -ENODEV;
> 

Best regards,
baolu
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