linux-ext4 - Re: [PATCH v1 6/9] lib: test_hmm add module param for zone device type

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Date:   Thu, 18 Nov 2021 18:19:16 +1100
From:   Alistair Popple <apopple@...dia.com>
To:     <akpm@...ux-foundation.org>, <Felix.Kuehling@....com>,
        <linux-mm@...ck.org>, <rcampbell@...dia.com>,
        <linux-ext4@...r.kernel.org>, <linux-xfs@...r.kernel.org>,
        Alex Sierra <alex.sierra@....com>
CC:     <amd-gfx@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
        <hch@....de>, <jgg@...dia.com>, <jglisse@...hat.com>,
        <willy@...radead.org>
Subject: Re: [PATCH v1 6/9] lib: test_hmm add module param for zone device type

On Tuesday, 16 November 2021 6:30:23 AM AEDT Alex Sierra wrote:
> In order to configure device coherent in test_hmm, two module parameters
> should be passed, which correspond to the SP start address of each
> device (2) spm_addr_dev0 & spm_addr_dev1. If no parameters are passed,
> private device type is configured.

Thanks for taking the time to add proper tests for this, as previously
mentioned I don't like the need for module parameters but understand why these
are more difficult to avoid.

However as also mentioned previously the restriction of being able to test only
private *or* coherent device pages is unnecessary and makes testing both types harder, especially if we need to test migration between device private and coherent pages.

<snip>
 
> -	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
> -				      "hmm_dmirror");
> -	if (IS_ERR(res))
> -		goto err_devmem;
> +	if (!spm_addr_dev0 && !spm_addr_dev1) {
> +		res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
> +					      "hmm_dmirror");
> +		if (IS_ERR_OR_NULL(res))
> +			goto err_devmem;
> +		devmem->pagemap.range.start = res->start;
> +		devmem->pagemap.range.end = res->end;
> +		devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
> +		mdevice->zone_device_type = HMM_DMIRROR_MEMORY_DEVICE_PRIVATE;
> +	} else if (spm_addr_dev0 && spm_addr_dev1) {
> +		devmem->pagemap.range.start = MINOR(mdevice->cdevice.dev) ?
> +							spm_addr_dev0 :
> +							spm_addr_dev1;

It seems like it would be fairly straight forward to address this concern by
adding extra minor character devices for the coherent devices. Would it be
possible for you to try that?

> +		devmem->pagemap.range.end = devmem->pagemap.range.start +
> +					    DEVMEM_CHUNK_SIZE - 1;
> +		devmem->pagemap.type = MEMORY_DEVICE_COHERENT;
> +		mdevice->zone_device_type = HMM_DMIRROR_MEMORY_DEVICE_COHERENT;
> +	} else {
> +		pr_err("Both spm_addr_dev parameters should be set\n");
> +	}
>  
> -	mdevice->zone_device_type = HMM_DMIRROR_MEMORY_DEVICE_PRIVATE;
> -	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
> -	devmem->pagemap.range.start = res->start;
> -	devmem->pagemap.range.end = res->end;
>  	devmem->pagemap.nr_range = 1;
>  	devmem->pagemap.ops = &dmirror_devmem_ops;
>  	devmem->pagemap.owner = mdevice;
> @@ -495,10 +517,14 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
>  		mdevice->devmem_capacity = new_capacity;
>  		mdevice->devmem_chunks = new_chunks;
>  	}
> -
>  	ptr = memremap_pages(&devmem->pagemap, numa_node_id());
> -	if (IS_ERR(ptr))
> +	if (IS_ERR_OR_NULL(ptr)) {
> +		if (ptr)
> +			ret = PTR_ERR(ptr);
> +		else
> +			ret = -EFAULT;
>  		goto err_release;
> +	}
>  
>  	devmem->mdevice = mdevice;
>  	pfn_first = devmem->pagemap.range.start >> PAGE_SHIFT;
> @@ -531,7 +557,8 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
>  
>  err_release:
>  	mutex_unlock(&mdevice->devmem_lock);
> -	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
> +	if (res)
> +		release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
>  err_devmem:
>  	kfree(devmem);
>  
> @@ -1219,10 +1246,8 @@ static int dmirror_device_init(struct dmirror_device *mdevice, int id)
>  	if (ret)
>  		return ret;
>  
> -	/* Build a list of free ZONE_DEVICE private struct pages */
> -	dmirror_allocate_chunk(mdevice, NULL);
> -
> -	return 0;
> +	/* Build a list of free ZONE_DEVICE struct pages */
> +	return dmirror_allocate_chunk(mdevice, NULL);
>  }
>  
>  static void dmirror_device_remove(struct dmirror_device *mdevice)
> @@ -1235,8 +1260,9 @@ static void dmirror_device_remove(struct dmirror_device *mdevice)
>  				mdevice->devmem_chunks[i];
>  
>  			memunmap_pages(&devmem->pagemap);
> -			release_mem_region(devmem->pagemap.range.start,
> -					   range_len(&devmem->pagemap.range));
> +			if (devmem->pagemap.type == MEMORY_DEVICE_PRIVATE)
> +				release_mem_region(devmem->pagemap.range.start,
> +						   range_len(&devmem->pagemap.range));
>  			kfree(devmem);
>  		}
>  		kfree(mdevice->devmem_chunks);
> diff --git a/lib/test_hmm_uapi.h b/lib/test_hmm_uapi.h
> index c42e57a6a71e..77f81e6314eb 100644
> --- a/lib/test_hmm_uapi.h
> +++ b/lib/test_hmm_uapi.h
> @@ -67,6 +67,7 @@ enum {
>  enum {
>  	/* 0 is reserved to catch uninitialized type fields */
>  	HMM_DMIRROR_MEMORY_DEVICE_PRIVATE = 1,
> +	HMM_DMIRROR_MEMORY_DEVICE_COHERENT,
>  };
>  
>  #endif /* _LIB_TEST_HMM_UAPI_H */
>