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From:   Alistair Popple <apopple@nvidia.com>
To:     <akpm@linux-foundation.org>, <Felix.Kuehling@amd.com>,
        <linux-mm@kvack.org>, <rcampbell@nvidia.com>,
        <linux-ext4@vger.kernel.org>, <linux-xfs@vger.kernel.org>,
        Alex Sierra <alex.sierra@amd.com>
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        <hch@lst.de>, <jgg@nvidia.com>, <jglisse@redhat.com>,
        <willy@infradead.org>
Subject: Re: [PATCH v3 09/10] tools: update hmm-test to support device coherent type
Date:   Thu, 20 Jan 2022 17:14:49 +1100
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On Tuesday, 11 January 2022 9:32:00 AM AEDT Alex Sierra wrote:
> Test cases such as migrate_fault and migrate_multiple, were modified to
> explicit migrate from device to sys memory without the need of page
> faults, when using device coherent type.
> 
> Snapshot test case updated to read memory device type first and based
> on that, get the proper returned results migrate_ping_pong test case

Where is the migrate_ping_pong test? Did you perhaps forget to add it? :-)

> added to test explicit migration from device to sys memory for both
> private and coherent zone types.
> 
> Helpers to migrate from device to sys memory and vicerversa
> were also added.
> 
> Signed-off-by: Alex Sierra <alex.sierra@amd.com>
> ---
> v2:
> Set FIXTURE_VARIANT to add multiple device types to the FIXTURE. This
> will run all the tests for each device type (private and coherent) in
> case both existed during hmm-test driver probed.
> ---
>  tools/testing/selftests/vm/hmm-tests.c | 122 ++++++++++++++++++++-----
>  1 file changed, 101 insertions(+), 21 deletions(-)
> 
> diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c
> index 864f126ffd78..8eb81dfba4b3 100644
> --- a/tools/testing/selftests/vm/hmm-tests.c
> +++ b/tools/testing/selftests/vm/hmm-tests.c
> @@ -44,6 +44,14 @@ struct hmm_buffer {
>  	int		fd;
>  	uint64_t	cpages;
>  	uint64_t	faults;
> +	int		zone_device_type;
> +};
> +
> +enum {
> +	HMM_PRIVATE_DEVICE_ONE,
> +	HMM_PRIVATE_DEVICE_TWO,
> +	HMM_COHERENCE_DEVICE_ONE,
> +	HMM_COHERENCE_DEVICE_TWO,
>  };
>  
>  #define TWOMEG		(1 << 21)
> @@ -60,6 +68,21 @@ FIXTURE(hmm)
>  	unsigned int	page_shift;
>  };
>  
> +FIXTURE_VARIANT(hmm)
> +{
> +	int     device_number;
> +};
> +
> +FIXTURE_VARIANT_ADD(hmm, hmm_device_private)
> +{
> +	.device_number = HMM_PRIVATE_DEVICE_ONE,
> +};
> +
> +FIXTURE_VARIANT_ADD(hmm, hmm_device_coherent)
> +{
> +	.device_number = HMM_COHERENCE_DEVICE_ONE,
> +};
> +
>  FIXTURE(hmm2)
>  {
>  	int		fd0;
> @@ -68,6 +91,24 @@ FIXTURE(hmm2)
>  	unsigned int	page_shift;
>  };
>  
> +FIXTURE_VARIANT(hmm2)
> +{
> +	int     device_number0;
> +	int     device_number1;
> +};
> +
> +FIXTURE_VARIANT_ADD(hmm2, hmm2_device_private)
> +{
> +	.device_number0 = HMM_PRIVATE_DEVICE_ONE,
> +	.device_number1 = HMM_PRIVATE_DEVICE_TWO,
> +};
> +
> +FIXTURE_VARIANT_ADD(hmm2, hmm2_device_coherent)
> +{
> +	.device_number0 = HMM_COHERENCE_DEVICE_ONE,
> +	.device_number1 = HMM_COHERENCE_DEVICE_TWO,
> +};
> +
>  static int hmm_open(int unit)
>  {
>  	char pathname[HMM_PATH_MAX];
> @@ -81,12 +122,19 @@ static int hmm_open(int unit)
>  	return fd;
>  }
>  
> +static bool hmm_is_coherent_type(int dev_num)
> +{
> +	return (dev_num >= HMM_COHERENCE_DEVICE_ONE);
> +}
> +
>  FIXTURE_SETUP(hmm)
>  {
>  	self->page_size = sysconf(_SC_PAGE_SIZE);
>  	self->page_shift = ffs(self->page_size) - 1;
>  
> -	self->fd = hmm_open(0);
> +	self->fd = hmm_open(variant->device_number);
> +	if (self->fd < 0 && hmm_is_coherent_type(variant->device_number))
> +		SKIP(exit(0), "DEVICE_COHERENT not available");
>  	ASSERT_GE(self->fd, 0);
>  }
>  
> @@ -95,9 +143,11 @@ FIXTURE_SETUP(hmm2)
>  	self->page_size = sysconf(_SC_PAGE_SIZE);
>  	self->page_shift = ffs(self->page_size) - 1;
>  
> -	self->fd0 = hmm_open(0);
> +	self->fd0 = hmm_open(variant->device_number0);
> +	if (self->fd0 < 0 && hmm_is_coherent_type(variant->device_number0))
> +		SKIP(exit(0), "DEVICE_COHERENT not available");
>  	ASSERT_GE(self->fd0, 0);
> -	self->fd1 = hmm_open(1);
> +	self->fd1 = hmm_open(variant->device_number1);
>  	ASSERT_GE(self->fd1, 0);
>  }
>  
> @@ -144,6 +194,7 @@ static int hmm_dmirror_cmd(int fd,
>  	}
>  	buffer->cpages = cmd.cpages;
>  	buffer->faults = cmd.faults;
> +	buffer->zone_device_type = cmd.zone_device_type;
>  
>  	return 0;
>  }
> @@ -211,6 +262,20 @@ static void hmm_nanosleep(unsigned int n)
>  	nanosleep(&t, NULL);
>  }
>  
> +static int hmm_migrate_sys_to_dev(int fd,
> +				   struct hmm_buffer *buffer,
> +				   unsigned long npages)
> +{
> +	return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE_TO_DEV, buffer, npages);
> +}
> +
> +static int hmm_migrate_dev_to_sys(int fd,
> +				   struct hmm_buffer *buffer,
> +				   unsigned long npages)
> +{
> +	return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE_TO_SYS, buffer, npages);
> +}
> +
>  /*
>   * Simple NULL test of device open/close.
>   */
> @@ -875,7 +940,7 @@ TEST_F(hmm, migrate)
>  		ptr[i] = i;
>  
>  	/* Migrate memory to device. */
> -	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
> +	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
>  	ASSERT_EQ(ret, 0);
>  	ASSERT_EQ(buffer->cpages, npages);
>  
> @@ -923,7 +988,7 @@ TEST_F(hmm, migrate_fault)
>  		ptr[i] = i;
>  
>  	/* Migrate memory to device. */
> -	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
> +	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
>  	ASSERT_EQ(ret, 0);
>  	ASSERT_EQ(buffer->cpages, npages);
>  
> @@ -936,7 +1001,7 @@ TEST_F(hmm, migrate_fault)
>  		ASSERT_EQ(ptr[i], i);
>  
>  	/* Migrate memory to the device again. */
> -	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
> +	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
>  	ASSERT_EQ(ret, 0);
>  	ASSERT_EQ(buffer->cpages, npages);
>  
> @@ -976,7 +1041,7 @@ TEST_F(hmm, migrate_shared)
>  	ASSERT_NE(buffer->ptr, MAP_FAILED);
>  
>  	/* Migrate memory to device. */
> -	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
> +	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
>  	ASSERT_EQ(ret, -ENOENT);
>  
>  	hmm_buffer_free(buffer);
> @@ -1015,7 +1080,7 @@ TEST_F(hmm2, migrate_mixed)
>  	p = buffer->ptr;
>  
>  	/* Migrating a protected area should be an error. */
> -	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, npages);
> +	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, npages);
>  	ASSERT_EQ(ret, -EINVAL);
>  
>  	/* Punch a hole after the first page address. */
> @@ -1023,7 +1088,7 @@ TEST_F(hmm2, migrate_mixed)
>  	ASSERT_EQ(ret, 0);
>  
>  	/* We expect an error if the vma doesn't cover the range. */
> -	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 3);
> +	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 3);
>  	ASSERT_EQ(ret, -EINVAL);
>  
>  	/* Page 2 will be a read-only zero page. */
> @@ -1055,13 +1120,13 @@ TEST_F(hmm2, migrate_mixed)
>  
>  	/* Now try to migrate pages 2-5 to device 1. */
>  	buffer->ptr = p + 2 * self->page_size;
> -	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 4);
> +	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 4);
>  	ASSERT_EQ(ret, 0);
>  	ASSERT_EQ(buffer->cpages, 4);
>  
>  	/* Page 5 won't be migrated to device 0 because it's on device 1. */
>  	buffer->ptr = p + 5 * self->page_size;
> -	ret = hmm_dmirror_cmd(self->fd0, HMM_DMIRROR_MIGRATE, buffer, 1);
> +	ret = hmm_migrate_sys_to_dev(self->fd0, buffer, 1);
>  	ASSERT_EQ(ret, -ENOENT);
>  	buffer->ptr = p;
>  
> @@ -1070,8 +1135,12 @@ TEST_F(hmm2, migrate_mixed)
>  }
>  
>  /*
> - * Migrate anonymous memory to device private memory and fault it back to system
> - * memory multiple times.
> + * Migrate anonymous memory to device memory and back to system memory
> + * multiple times. In case of private zone configuration, this is done
> + * through fault pages accessed by CPU. In case of coherent zone configuration,
> + * the pages from the device should be explicitly migrated back to system memory.
> + * The reason is Coherent device zone has coherent access by CPU, therefore
> + * it will not generate any page fault.
>   */
>  TEST_F(hmm, migrate_multiple)
>  {
> @@ -1107,8 +1176,7 @@ TEST_F(hmm, migrate_multiple)
>  			ptr[i] = i;
>  
>  		/* Migrate memory to device. */
> -		ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer,
> -				      npages);
> +		ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
>  		ASSERT_EQ(ret, 0);
>  		ASSERT_EQ(buffer->cpages, npages);
>  
> @@ -1116,7 +1184,12 @@ TEST_F(hmm, migrate_multiple)
>  		for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
>  			ASSERT_EQ(ptr[i], i);
>  
> -		/* Fault pages back to system memory and check them. */
> +		/* Migrate back to system memory and check them. */
> +		if (hmm_is_coherent_type(variant->device_number)) {
> +			ret = hmm_migrate_dev_to_sys(self->fd, buffer, npages);

So I think this will still pass even if nothing migrates so as mentioned on
the previous patch I think we need to check for the number of pages that
actually migrated. Alternatively I suppose you could do a snapshot and check
that, but that seems like it would be harder. Otherwise I think this looks
good.

> +			ASSERT_EQ(ret, 0);
> +		}
> +
>  		for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
>  			ASSERT_EQ(ptr[i], i);
>  
> @@ -1312,13 +1385,13 @@ TEST_F(hmm2, snapshot)
>  
>  	/* Page 5 will be migrated to device 0. */
>  	buffer->ptr = p + 5 * self->page_size;
> -	ret = hmm_dmirror_cmd(self->fd0, HMM_DMIRROR_MIGRATE, buffer, 1);
> +	ret = hmm_migrate_sys_to_dev(self->fd0, buffer, 1);
>  	ASSERT_EQ(ret, 0);
>  	ASSERT_EQ(buffer->cpages, 1);
>  
>  	/* Page 6 will be migrated to device 1. */
>  	buffer->ptr = p + 6 * self->page_size;
> -	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 1);
> +	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 1);
>  	ASSERT_EQ(ret, 0);
>  	ASSERT_EQ(buffer->cpages, 1);
>  
> @@ -1335,9 +1408,16 @@ TEST_F(hmm2, snapshot)
>  	ASSERT_EQ(m[2], HMM_DMIRROR_PROT_ZERO | HMM_DMIRROR_PROT_READ);
>  	ASSERT_EQ(m[3], HMM_DMIRROR_PROT_READ);
>  	ASSERT_EQ(m[4], HMM_DMIRROR_PROT_WRITE);
> -	ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL |
> -			HMM_DMIRROR_PROT_WRITE);
> -	ASSERT_EQ(m[6], HMM_DMIRROR_PROT_NONE);
> +	if (!hmm_is_coherent_type(variant->device_number0)) {
> +		ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL |
> +				HMM_DMIRROR_PROT_WRITE);
> +		ASSERT_EQ(m[6], HMM_DMIRROR_PROT_NONE);
> +	} else {
> +		ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_COHERENT_LOCAL |
> +				HMM_DMIRROR_PROT_WRITE);
> +		ASSERT_EQ(m[6], HMM_DMIRROR_PROT_DEV_COHERENT_REMOTE |
> +				HMM_DMIRROR_PROT_WRITE);
> +	}
>  
>  	hmm_buffer_free(buffer);
>  }
>