Re: [PATCH v2 09/12] lib: test_hmm add module param for zone device type

Sierra Guiza, Alejandro (Alex)
2021-09-23T15:52:58Z

On 9/21/2021 12:14 AM, Alistair Popple wrote:
> On Tuesday, 21 September 2021 6:05:30 AM AEST Sierra Guiza, Alejandro (Alex) wrote:
>> On 9/20/2021 3:53 AM, Alistair Popple wrote:
>>> On Tuesday, 14 September 2021 2:16:01 AM AEST Alex Sierra wrote:
>>>> In order to configure device public 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.
>>> It's a pity that testing this seems to require some amount of special setup to
>>> test. Is there a way this could be made to work on a more standard setup
>>> similar to how DEVICE_PRIVATE is tested?
>> Hi Alistair
>> We tried to do it as simpler as possible. Unfortunately, there are two main
>> requirements to register dev memory as DEVICE_PUBLIC type. This memory must
>> NOT be accessed by any memory allocator (SLAB, SLOB, SLUB) plus, it has
>> to be
>> CPU coherently accessed. We also want to avoid aliasing the same PFNs for
>> different page types (regular system memory and DEVICE_PUBLIC). So we don't
>> want the reserved memory to be part of the kernel's memory map before we
>> call
>> memremap_pages. A transparent way of doing it, without any special HW, was
>> setting a portion of system memory as SPM (Special purpose memory). And use
>> this as our “device fake” memory.
> Ok, I think it's great that we can test this without special HW but the boot
> time configuration is still a bit annoying. Would it be possible to allocate
> memory fitting the above requirements by hot unplugging it with something like
> offline_and_remove_memory()?
>
> I also don't see why the DEVICE_PRIVATE and DEVICE_PUBLIC testing should be
> mutually exclusive - why can't we test both without reloading the module?
You could do both DEVICE_PRIVATE and DEVICE_PUBLIC tests by running the
test_hmm_sh
script twice, just passing the proper parameters. Even when you booted
with fake EFI SP
regions. If spm_address_dev0/1 parameters are passed, the module gets
configured with
DEVICE_PUBLIC type. Otherwise DEVICE_PRIVATE type is set. Technically
the only
complication in testing DEVICE_PUBLIC is the fake SPM boot parameter.

Alex Sierra
>
> - Alistair
>
>> Regards,
>> Alex Sierra
>>
>>>> Signed-off-by: Alex Sierra <alex.sierra@amd.com>
>>>> ---
>>>> v5:
>>>> Remove devmem->pagemap.type = MEMORY_DEVICE_PRIVATE at
>>>> dmirror_allocate_chunk that was forcing to configure pagemap.type
>>>> to MEMORY_DEVICE_PRIVATE
>>>>
>>>> v6:
>>>> Check for null pointers for resource and memremap references
>>>> at dmirror_allocate_chunk
>>>>
>>>> v7:
>>>> Due to patch dropped from these patch series "kernel: resource:
>>>> lookup_resource as exported symbol", lookup_resource was not longer a
>>>> callable function. This was used in public device configuration, to
>>>> get start and end addresses, to create pgmap->range struct. This
>>>> information is now taken directly from the spm_addr_devX parameters and
>>>> the fixed size DEVMEM_CHUNK_SIZE.
>>>> ---
>>>> lib/test_hmm.c | 66 +++++++++++++++++++++++++++++++--------------
>>>> lib/test_hmm_uapi.h | 1 +
>>>> 2 files changed, 47 insertions(+), 20 deletions(-)
>>>>
>>>> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
>>>> index 3cd91ca31dd7..ef27e355738a 100644
>>>> --- a/lib/test_hmm.c
>>>> +++ b/lib/test_hmm.c
>>>> @@ -33,6 +33,16 @@
>>>> #define DEVMEM_CHUNK_SIZE (256 * 1024 * 1024U)
>>>> #define DEVMEM_CHUNKS_RESERVE 16
>>>>
>>>> +static unsigned long spm_addr_dev0;
>>>> +module_param(spm_addr_dev0, long, 0644);
>>>> +MODULE_PARM_DESC(spm_addr_dev0,
>>>> + "Specify start address for SPM (special purpose memory) used for device 0. By setting this Generic device type will be used. Make sure spm_addr_dev1 is set too");
>>>> +
>>>> +static unsigned long spm_addr_dev1;
>>>> +module_param(spm_addr_dev1, long, 0644);
>>>> +MODULE_PARM_DESC(spm_addr_dev1,
>>>> + "Specify start address for SPM (special purpose memory) used for device 1. By setting this Generic device type will be used. Make sure spm_addr_dev0 is set too");
>>>> +
>>>> static const struct dev_pagemap_ops dmirror_devmem_ops;
>>>> static const struct mmu_interval_notifier_ops dmirror_min_ops;
>>>> static dev_t dmirror_dev;
>>>> @@ -450,11 +460,11 @@ static int dmirror_write(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
>>>> return ret;
>>>> }
>>>>
>>>> -static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
>>>> +static int dmirror_allocate_chunk(struct dmirror_device *mdevice,
>>>> struct page **ppage)
>>>> {
>>>> struct dmirror_chunk *devmem;
>>>> - struct resource *res;
>>>> + struct resource *res = NULL;
>>>> unsigned long pfn;
>>>> unsigned long pfn_first;
>>>> unsigned long pfn_last;
>>>> @@ -462,17 +472,29 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
>>>>
>>>> devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
>>>> if (!devmem)
>>>> - return false;
>>>> + return -ENOMEM;
>>>>
>>>> - 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;
>>>> + devmem->pagemap.range.end = devmem->pagemap.range.start +
>>>> + DEVMEM_CHUNK_SIZE - 1;
>>>> + devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
>>>> + mdevice->zone_device_type = HMM_DMIRROR_MEMORY_DEVICE_PUBLIC;
>>>> + } 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;
>>>> @@ -493,10 +515,14 @@ 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;
>>>> @@ -529,7 +555,8 @@ 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);
>>>>
>>>> @@ -1097,10 +1124,8 @@ 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)
>>>> @@ -1113,8 +1138,9 @@ 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 ee88701793d5..00259d994410 100644
>>>> --- a/lib/test_hmm_uapi.h
>>>> +++ b/lib/test_hmm_uapi.h
>>>> @@ -65,6 +65,7 @@ enum {
>>>> enum {
>>>> /* 0 is reserved to catch uninitialized type fields */
>>>> HMM_DMIRROR_MEMORY_DEVICE_PRIVATE = 1,
>>>> + HMM_DMIRROR_MEMORY_DEVICE_PUBLIC,
>>>> };
>>>>
>>>> #endif /* _LIB_TEST_HMM_UAPI_H */
>>>>
>>>
>>>
>
>
>