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

Alistair Popple
2021-10-01T00:28:47Z

On Friday, 24 September 2021 1:52:47 AM AEST Sierra Guiza, Alejandro (Alex) wrote:
>
> 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.

Or you could just have the test specify what sort of memory it wants to use
(DEVICE_PRIVATE or DEVICE_GENERIC). That seems preferable to requiring a module
reload. A module reload also makes it impossible to test interactions between
DEVICE_PRIVATE and DEVICE_GENERIC memory.

- Alistair

> 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 */
> >>>>
> >>>
> >>>
> >
> >
> >
>