From: John Hubbard <jhubbard@nvidia.com>
To: "Jérôme Glisse" <jglisse@redhat.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Cc: Dan Williams <dan.j.williams@intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Evgeny Baskakov <ebaskakov@nvidia.com>,
Mark Hairgrove <mhairgrove@nvidia.com>,
Sherry Cheung <SCheung@nvidia.com>,
Subhash Gutti <sgutti@nvidia.com>Evgeny Baskakov
<ebaskakov@nvidia.com>
Subject: Re: [HMM 09/15] mm/hmm/devmem: device memory hotplug using ZONE_DEVICE v5
Date: Fri, 23 Jun 2017 20:54:44 -0700 [thread overview]
Message-ID: <64f74f48-ca5e-e16d-7546-0d57163f6f93@nvidia.com> (raw)
In-Reply-To: <20170524172024.30810-10-jglisse@redhat.com>
On 05/24/2017 10:20 AM, Jérôme Glisse wrote:
[...]
> +/*
> + * hmm_devmem_fault_range() - migrate back a virtual range of memory
> + *
> + * @devmem: hmm_devmem struct use to track and manage the ZONE_DEVICE memory
> + * @vma: virtual memory area containing the range to be migrated
> + * @ops: migration callback for allocating destination memory and copying
> + * @src: array of unsigned long containing source pfns
> + * @dst: array of unsigned long containing destination pfns
> + * @start: start address of the range to migrate (inclusive)
> + * @addr: fault address (must be inside the range)
> + * @end: end address of the range to migrate (exclusive)
> + * @private: pointer passed back to each of the callback
> + * Returns: 0 on success, VM_FAULT_SIGBUS on error
> + *
> + * This is a wrapper around migrate_vma() which checks the migration status
> + * for a given fault address and returns the corresponding page fault handler
> + * status. That will be 0 on success, or VM_FAULT_SIGBUS if migration failed
> + * for the faulting address.
> + *
> + * This is a helper intendend to be used by the ZONE_DEVICE fault handler.
> + */
> +int hmm_devmem_fault_range(struct hmm_devmem *devmem,
> + struct vm_area_struct *vma,
> + const struct migrate_vma_ops *ops,
> + unsigned long *src,
> + unsigned long *dst,
> + unsigned long start,
> + unsigned long addr,
> + unsigned long end,
> + void *private)
> +{
> + if (migrate_vma(ops, vma, start, end, src, dst, private))
> + return VM_FAULT_SIGBUS;
> +
> + if (dst[(addr - start) >> PAGE_SHIFT] & MIGRATE_PFN_ERROR)
> + return VM_FAULT_SIGBUS;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(hmm_devmem_fault_range);
> +#endif /* IS_ENABLED(CONFIG_HMM_DEVMEM) */
>
Hi Jerome (+Evgeny),
After some time and testing, I'd like to recommend that we delete the above
hmm_dev_fault_range() function from the patchset. Reasons:
1. Our driver code is actually easier to follow if we call migrate_vma() directly, for CPU
faults. That's because there are a lot of hmm_* calls in both directions (driver <-->
core), already, and it takes some time to remember which direction each one goes.
2. The helper is a little confusing to use, what with a start, end, *and* an addr argument.
3. ...and it doesn't add anything that the driver can't trivially do itself.
So, let's just remove it. Less is more this time. :)
thanks,
--
John Hubbard
NVIDIA
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next prev parent reply other threads:[~2017-06-24 3:54 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-24 17:20 [HMM 00/15] HMM (Heterogeneous Memory Management) v23 Jérôme Glisse
2017-05-24 17:20 ` [HMM 01/15] hmm: heterogeneous memory management documentation Jérôme Glisse
2017-06-24 6:15 ` John Hubbard
2017-05-24 17:20 ` [HMM 02/15] mm/hmm: heterogeneous memory management (HMM for short) v4 Jérôme Glisse
2017-05-31 2:10 ` Balbir Singh
2017-06-01 22:35 ` Jerome Glisse
2017-05-24 17:20 ` [HMM 03/15] mm/hmm/mirror: mirror process address space on device with HMM helpers v3 Jérôme Glisse
2017-05-24 17:20 ` [HMM 04/15] mm/hmm/mirror: helper to snapshot CPU page table v3 Jérôme Glisse
2017-05-24 17:20 ` [HMM 05/15] mm/hmm/mirror: device page fault handler Jérôme Glisse
2017-05-24 17:20 ` [HMM 06/15] mm/memory_hotplug: introduce add_pages Jérôme Glisse
2017-05-31 1:31 ` Balbir Singh
2017-05-24 17:20 ` [HMM 07/15] mm/ZONE_DEVICE: new type of ZONE_DEVICE for unaddressable memory v3 Jérôme Glisse
2017-05-30 16:43 ` Ross Zwisler
2017-05-30 21:43 ` Jerome Glisse
2017-05-31 1:23 ` Balbir Singh
2017-06-09 3:55 ` John Hubbard
2017-06-12 17:57 ` Jerome Glisse
2017-06-15 3:41 ` zhong jiang
2017-06-15 17:43 ` Jerome Glisse
2017-05-24 17:20 ` [HMM 08/15] mm/ZONE_DEVICE: special case put_page() for device private pages v2 Jérôme Glisse
2017-05-24 17:20 ` [HMM 09/15] mm/hmm/devmem: device memory hotplug using ZONE_DEVICE v5 Jérôme Glisse
2017-06-24 3:54 ` John Hubbard [this message]
2017-05-24 17:20 ` [HMM 10/15] mm/hmm/devmem: dummy HMM device for ZONE_DEVICE memory v3 Jérôme Glisse
2017-05-24 17:20 ` [HMM 11/15] mm/migrate: new migrate mode MIGRATE_SYNC_NO_COPY Jérôme Glisse
2017-05-24 17:20 ` [HMM 12/15] mm/migrate: new memory migration helper for use with device memory v4 Jérôme Glisse
2017-05-31 3:59 ` Balbir Singh
2017-06-01 22:35 ` Jerome Glisse
2017-06-07 9:02 ` Balbir Singh
2017-06-07 14:06 ` Jerome Glisse
2017-05-24 17:20 ` [HMM 13/15] mm/migrate: migrate_vma() unmap page from vma while collecting pages Jérôme Glisse
2017-05-24 17:20 ` [HMM 14/15] mm/migrate: support un-addressable ZONE_DEVICE page in migration v2 Jérôme Glisse
2017-05-31 4:09 ` Balbir Singh
2017-05-31 8:39 ` Balbir Singh
2017-05-24 17:20 ` [HMM 15/15] mm/migrate: allow migrate_vma() to alloc new page on empty entry v2 Jérôme Glisse
2017-06-16 7:22 ` [HMM 00/15] HMM (Heterogeneous Memory Management) v23 Bridgman, John
2017-06-16 14:47 ` Jerome Glisse
2017-06-16 17:55 ` Bridgman, John
2017-06-16 18:04 ` Jerome Glisse
2017-06-23 15:00 ` Bob Liu
2017-06-23 15:28 ` Jerome Glisse
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