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From: Jerome Glisse <jglisse@redhat.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: thomas.lendacky@amd.com, dave@sr71.net,
	linux-nvdimm@lists.01.org, tiwai@suse.de,
	Dave Hansen <dave.hansen@linux.intel.com>,
	ying.huang@intel.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, mhocko@suse.com, bp@suse.de,
	baiyaowei@cmss.chinamobile.com, zwisler@kernel.org,
	bhelgaas@google.com, fengguang.wu@intel.com,
	akpm@linux-foundation.org
Subject: Re: [PATCH 2/4] mm/memory-hotplug: allow memory resources to be children
Date: Fri, 18 Jan 2019 15:26:18 -0500	[thread overview]
Message-ID: <20190118202618.GB3060@redhat.com> (raw)
In-Reply-To: <c6df9b8d-571d-3b4f-c528-dc176f8577e2@intel.com>

On Fri, Jan 18, 2019 at 11:58:54AM -0800, Dave Hansen wrote:
> On 1/16/19 11:16 AM, Jerome Glisse wrote:
> >> We *could* also simply truncate the existing top-level
> >> "Persistent Memory" resource and take over the released address
> >> space.  But, this means that if we ever decide to hot-unplug the
> >> "RAM" and give it back, we need to recreate the original setup,
> >> which may mean going back to the BIOS tables.
> >>
> >> This should have no real effect on the existing collision
> >> detection because the areas that truly conflict should be marked
> >> IORESOURCE_BUSY.
> > 
> > Still i am worrying that this might allow device private to register
> > itself as a child of some un-busy resource as this patch obviously
> > change the behavior of register_memory_resource()
> > 
> > What about instead explicitly providing parent resource to add_memory()
> > and then to register_memory_resource() so if it is provided as an
> > argument (!NULL) then you can __request_region(arg_res, ...) otherwise
> > you keep existing code intact ?
> 
> We don't have the locking to do this, do we?  For instance, all the
> locking is done below register_memory_resource(), so any previous
> resource lookup is invalid by the time we get to register_memory_resource().

Yeah you are right, maybe just a bool then ? bool as_child

Cheers,
Jérôme
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WARNING: multiple messages have this Message-ID (diff)
From: Jerome Glisse <jglisse@redhat.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
	dave@sr71.net, dan.j.williams@intel.com, dave.jiang@intel.com,
	zwisler@kernel.org, vishal.l.verma@intel.com,
	thomas.lendacky@amd.com, akpm@linux-foundation.org,
	mhocko@suse.com, linux-nvdimm@lists.01.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	ying.huang@intel.com, fengguang.wu@intel.com, bp@suse.de,
	bhelgaas@google.com, baiyaowei@cmss.chinamobile.com,
	tiwai@suse.de
Subject: Re: [PATCH 2/4] mm/memory-hotplug: allow memory resources to be children
Date: Fri, 18 Jan 2019 15:26:18 -0500	[thread overview]
Message-ID: <20190118202618.GB3060@redhat.com> (raw)
In-Reply-To: <c6df9b8d-571d-3b4f-c528-dc176f8577e2@intel.com>

On Fri, Jan 18, 2019 at 11:58:54AM -0800, Dave Hansen wrote:
> On 1/16/19 11:16 AM, Jerome Glisse wrote:
> >> We *could* also simply truncate the existing top-level
> >> "Persistent Memory" resource and take over the released address
> >> space.  But, this means that if we ever decide to hot-unplug the
> >> "RAM" and give it back, we need to recreate the original setup,
> >> which may mean going back to the BIOS tables.
> >>
> >> This should have no real effect on the existing collision
> >> detection because the areas that truly conflict should be marked
> >> IORESOURCE_BUSY.
> > 
> > Still i am worrying that this might allow device private to register
> > itself as a child of some un-busy resource as this patch obviously
> > change the behavior of register_memory_resource()
> > 
> > What about instead explicitly providing parent resource to add_memory()
> > and then to register_memory_resource() so if it is provided as an
> > argument (!NULL) then you can __request_region(arg_res, ...) otherwise
> > you keep existing code intact ?
> 
> We don't have the locking to do this, do we?  For instance, all the
> locking is done below register_memory_resource(), so any previous
> resource lookup is invalid by the time we get to register_memory_resource().

Yeah you are right, maybe just a bool then ? bool as_child

Cheers,
Jérôme

  reply	other threads:[~2019-01-18 20:26 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-16 18:18 [PATCH 0/4] Allow persistent memory to be used like normal RAM Dave Hansen
2019-01-16 18:18 ` Dave Hansen
2019-01-16 18:18 ` Dave Hansen
2019-01-16 18:19 ` [PATCH 1/4] mm/resource: return real error codes from walk failures Dave Hansen
2019-01-16 18:19   ` Dave Hansen
2019-01-16 18:19   ` Dave Hansen
     [not found]   ` <20190116181901.CAF85066-LXbPSdftPKxrdx17CPfAsdBPR1lH4CV8@public.gmane.org>
2019-01-16 20:38     ` Bjorn Helgaas
2019-01-16 20:38       ` Bjorn Helgaas
2019-01-16 18:19 ` [PATCH 2/4] mm/memory-hotplug: allow memory resources to be children Dave Hansen
2019-01-16 18:19   ` Dave Hansen
2019-01-16 18:19   ` Dave Hansen
2019-01-16 19:16   ` Jerome Glisse
2019-01-16 19:16     ` Jerome Glisse
2019-01-16 23:01     ` Dave Hansen
2019-01-16 23:01       ` Dave Hansen
2019-01-16 23:38       ` Jerome Glisse
2019-01-16 23:38         ` Jerome Glisse
2019-01-23 20:03         ` Dave Hansen
2019-01-23 20:03           ` Dave Hansen
2019-01-23 20:15           ` Jerome Glisse
2019-01-23 20:15             ` Jerome Glisse
2019-01-18 19:58     ` Dave Hansen
2019-01-18 19:58       ` Dave Hansen
2019-01-18 20:26       ` Jerome Glisse [this message]
2019-01-18 20:26         ` Jerome Glisse
2019-01-23 17:05   ` Michal Hocko
2019-01-16 18:19 ` [PATCH 3/4] dax/kmem: let walk_system_ram_range() search child resources Dave Hansen
2019-01-16 18:19   ` Dave Hansen
2019-01-16 18:19   ` Dave Hansen
     [not found] ` <20190116181859.D1504459-LXbPSdftPKxrdx17CPfAsdBPR1lH4CV8@public.gmane.org>
2019-01-16 18:19   ` [PATCH 4/4] dax: "Hotplug" persistent memory for use like normal RAM Dave Hansen
2019-01-16 18:19     ` Dave Hansen
2019-01-16 18:19     ` Dave Hansen
2019-01-16 21:16     ` Bjorn Helgaas
2019-01-16 21:40       ` Dave Hansen
2019-01-16 21:40         ` Dave Hansen
     [not found]         ` <98ab9bc8-8a17-297c-da7c-2e6b5a03ef24-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2019-01-16 21:44           ` Bjorn Helgaas
2019-01-16 21:44             ` Bjorn Helgaas
2019-01-16 22:06         ` Dan Williams
2019-01-16 22:06           ` Dan Williams
2019-01-16 21:53       ` Dave Hansen
2019-01-16 21:53         ` Dave Hansen
2019-01-16 21:59         ` Bjorn Helgaas
2019-01-16 21:31     ` Dan Williams
2019-01-16 21:31       ` Dan Williams
2019-01-17  5:21     ` Du, Fan
2019-01-17  5:21       ` Du, Fan
2019-01-17 16:56       ` Dan Williams
2019-01-17 16:56         ` Dan Williams
2019-01-17  8:19     ` Yanmin Zhang
2019-01-17  8:19       ` Yanmin Zhang
2019-01-17 15:17       ` Dave Hansen
2019-01-18  7:47         ` Yanmin Zhang
2019-01-18  7:47           ` Yanmin Zhang
2019-01-18 15:20           ` Dave Hansen
2019-01-17 16:29 ` [PATCH 0/4] Allow persistent memory to be used " Jeff Moyer
2019-01-17 16:29   ` Jeff Moyer
2019-01-17 16:47   ` Keith Busch
2019-01-17 16:47     ` Keith Busch
2019-01-17 17:20     ` Jeff Moyer
2019-01-17 19:34       ` Keith Busch
2019-01-17 19:34         ` Keith Busch
2019-01-17 21:57         ` Jeff Moyer
2019-01-17 21:57           ` Jeff Moyer
2019-01-18 11:48       ` Fengguang Wu
2019-01-18 11:48         ` Fengguang Wu
2019-01-17 16:50   ` Dan Williams
2019-01-17 16:50     ` Dan Williams
2019-01-17 22:43   ` Dave Hansen
2019-01-17 22:43     ` Dave Hansen

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