From: Balbir Singh <bsingharora@gmail.com>
To: Jerome Glisse <jglisse@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
John Hubbard <jhubbard@nvidia.com>,
David Nellans <dnellans@nvidia.com>,
Dan Williams <dan.j.williams@intel.com>,
Balbir Singh <balbirs@au1.ibm.com>,
Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Ross Zwisler <ross.zwisler@linux.intel.com>
Subject: Re: [PATCH 2/5] mm/device-public-memory: device memory cache coherent with CPU v2
Date: Wed, 12 Jul 2017 15:50:15 +1000 [thread overview]
Message-ID: <20170712155015.2b77f958@firefly.ozlabs.ibm.com> (raw)
In-Reply-To: <20170711145744.GA5347@redhat.com>
On Tue, 11 Jul 2017 10:57:44 -0400
Jerome Glisse <jglisse@redhat.com> wrote:
> On Tue, Jul 11, 2017 at 02:12:15PM +1000, Balbir Singh wrote:
> > On Mon, 3 Jul 2017 17:14:12 -0400
> > Jérôme Glisse <jglisse@redhat.com> wrote:
> >
> > > Platform with advance system bus (like CAPI or CCIX) allow device
> > > memory to be accessible from CPU in a cache coherent fashion. Add
> > > a new type of ZONE_DEVICE to represent such memory. The use case
> > > are the same as for the un-addressable device memory but without
> > > all the corners cases.
> > >
> >
> > Looks good overall, some comments inline.
> >
>
> [...]
>
> > > /*
> > > @@ -92,6 +100,8 @@ enum memory_type {
> > > * The page_free() callback is called once the page refcount reaches 1
> > > * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.
> > > * This allows the device driver to implement its own memory management.)
> > > + *
> > > + * For MEMORY_DEVICE_CACHE_COHERENT only the page_free() callback matter.
> >
> > Correct, but I wonder if we should in the long term allow for minor faults
> > (due to coherency) via this interface?
>
> This is something we can explore latter on.
>
> [...]
>
Agreed
> > > diff --git a/kernel/memremap.c b/kernel/memremap.c
> > > index e82456c39a6a..da74775f2247 100644
> > > --- a/kernel/memremap.c
> > > +++ b/kernel/memremap.c
> > > @@ -466,7 +466,7 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
> > >
> > >
> > > #ifdef CONFIG_DEVICE_PRIVATE
> >
> > Does the #ifdef above need to go as well?
>
> Good catch i should make that conditional on DEVICE_PUBLIC or whatever
> the name endup to be. I will make sure i test without DEVICE_PRIVATE
> config before posting again.
>
> [...]
>
I've been testing with this off, I should have sent you a patch, but
I thought I'd also update in the review.
> > > @@ -2541,11 +2551,21 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
> > > */
> > > __SetPageUptodate(page);
> > >
> > > - if (is_zone_device_page(page) && is_device_private_page(page)) {
> > > - swp_entry_t swp_entry;
> > > + if (is_zone_device_page(page)) {
> > > + if (is_device_private_page(page)) {
> > > + swp_entry_t swp_entry;
> > >
> > > - swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
> > > - entry = swp_entry_to_pte(swp_entry);
> > > + swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
> > > + entry = swp_entry_to_pte(swp_entry);
> > > + }
> > > +#if IS_ENABLED(CONFIG_DEVICE_PUBLIC)
> >
> > Do we need this #if check? is_device_public_page(page)
> > will return false if the config is disabled
>
> pte_mkdevmap() is not define if ZONE_DEVICE is not enabled hence
> i had to protect this with #if/#endif to avoid build error.
pte_mkdevmap is always defined, could you please share the build
error.
Balbir Singh.
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next prev parent reply other threads:[~2017-07-12 5:50 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-03 21:14 [PATCH 0/5] Cache coherent device memory (CDM) with HMM v3 Jérôme Glisse
2017-07-03 21:14 ` [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum memory_type one Jérôme Glisse
2017-07-03 23:49 ` Dan Williams
2017-07-05 14:25 ` Jerome Glisse
2017-07-05 16:15 ` Dan Williams
2017-07-05 18:49 ` Jerome Glisse
2017-07-11 3:48 ` Balbir Singh
2017-07-11 7:31 ` Dan Williams
2017-07-11 15:05 ` Jerome Glisse
2017-07-11 16:49 ` Dan Williams
2017-07-03 21:14 ` [PATCH 2/5] mm/device-public-memory: device memory cache coherent with CPU v2 Jérôme Glisse
2017-07-11 4:12 ` Balbir Singh
2017-07-11 14:57 ` Jerome Glisse
2017-07-12 5:50 ` Balbir Singh [this message]
2017-07-03 21:14 ` [PATCH 3/5] mm/hmm: add new helper to hotplug CDM memory region Jérôme Glisse
2017-07-03 21:14 ` [PATCH 4/5] mm/memcontrol: allow to uncharge page without using page->lru field Jérôme Glisse
2017-07-04 12:51 ` Michal Hocko
2017-07-05 3:18 ` Balbir Singh
2017-07-05 6:38 ` Michal Hocko
2017-07-05 10:22 ` Balbir Singh
2017-07-05 14:35 ` Jerome Glisse
2017-07-10 8:28 ` Michal Hocko
2017-07-10 15:32 ` Jerome Glisse
2017-07-10 16:04 ` Michal Hocko
2017-07-10 16:25 ` Jerome Glisse
2017-07-10 16:36 ` Michal Hocko
2017-07-10 16:54 ` Jerome Glisse
2017-07-10 17:48 ` Michal Hocko
2017-07-10 18:10 ` Jerome Glisse
2017-07-03 21:14 ` [PATCH 5/5] mm/memcontrol: support MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_PUBLIC Jérôme Glisse
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