From: Jerome Glisse <jglisse@redhat.com>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: 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: Wed, 16 Jan 2019 14:16:36 -0500 [thread overview]
Message-ID: <20190116191635.GD3617@redhat.com> (raw)
In-Reply-To: <20190116181902.670EEBC3@viggo.jf.intel.com>
On Wed, Jan 16, 2019 at 10:19:02AM -0800, Dave Hansen wrote:
>
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> The mm/resource.c code is used to manage the physical address
> space. We can view the current resource configuration in
> /proc/iomem. An example of this is at the bottom of this
> description.
>
> The nvdimm subsystem "owns" the physical address resources which
> map to persistent memory and has resources inserted for them as
> "Persistent Memory". We want to use this persistent memory, but
> as volatile memory, just like RAM. The best way to do this is
> to leave the existing resource in place, but add a "System RAM"
> resource underneath it. This clearly communicates the ownership
> relationship of this memory.
>
> The request_resource_conflict() API only deals with the
> top-level resources. Replace it with __request_region() which
> will search for !IORESOURCE_BUSY areas lower in the resource
> tree than the top level.
>
> We also rework the old error message a bit since we do not get
> the conflicting entry back: only an indication that we *had* a
> conflict.
We should keep the device private check (moving it in __request_region)
as device private can try to register un-use physical address (un-use
at time of device private registration) that latter can block valid
physical address the error message you are removing report such event.
>
> 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 ?
Cheers,
Jérôme
>
> 00000000-00000fff : Reserved
> 00001000-0009fbff : System RAM
> 0009fc00-0009ffff : Reserved
> 000a0000-000bffff : PCI Bus 0000:00
> 000c0000-000c97ff : Video ROM
> 000c9800-000ca5ff : Adapter ROM
> 000f0000-000fffff : Reserved
> 000f0000-000fffff : System ROM
> 00100000-9fffffff : System RAM
> 01000000-01e071d0 : Kernel code
> 01e071d1-027dfdff : Kernel data
> 02dc6000-0305dfff : Kernel bss
> a0000000-afffffff : Persistent Memory (legacy)
> a0000000-a7ffffff : System RAM
> b0000000-bffdffff : System RAM
> bffe0000-bfffffff : Reserved
> c0000000-febfffff : PCI Bus 0000:00
>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Ross Zwisler <zwisler@kernel.org>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: linux-nvdimm@lists.01.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: Huang Ying <ying.huang@intel.com>
> Cc: Fengguang Wu <fengguang.wu@intel.com>
>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> ---
>
> b/mm/memory_hotplug.c | 31 ++++++++++++++-----------------
> 1 file changed, 14 insertions(+), 17 deletions(-)
>
> diff -puN mm/memory_hotplug.c~mm-memory-hotplug-allow-memory-resource-to-be-child mm/memory_hotplug.c
> --- a/mm/memory_hotplug.c~mm-memory-hotplug-allow-memory-resource-to-be-child 2018-12-20 11:48:42.317771933 -0800
> +++ b/mm/memory_hotplug.c 2018-12-20 11:48:42.322771933 -0800
> @@ -98,24 +98,21 @@ void mem_hotplug_done(void)
> /* add this memory to iomem resource */
> static struct resource *register_memory_resource(u64 start, u64 size)
> {
> - struct resource *res, *conflict;
> - res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> - if (!res)
> - return ERR_PTR(-ENOMEM);
> + struct resource *res;
> + unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> + char *resource_name = "System RAM";
>
> - res->name = "System RAM";
> - res->start = start;
> - res->end = start + size - 1;
> - res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> - conflict = request_resource_conflict(&iomem_resource, res);
> - if (conflict) {
> - if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) {
> - pr_debug("Device unaddressable memory block "
> - "memory hotplug at %#010llx !\n",
> - (unsigned long long)start);
> - }
> - pr_debug("System RAM resource %pR cannot be added\n", res);
> - kfree(res);
> + /*
> + * Request ownership of the new memory range. This might be
> + * a child of an existing resource that was present but
> + * not marked as busy.
> + */
> + res = __request_region(&iomem_resource, start, size,
> + resource_name, flags);
> +
> + if (!res) {
> + pr_debug("Unable to reserve System RAM region: %016llx->%016llx\n",
> + start, start + size);
> return ERR_PTR(-EEXIST);
> }
> return res;
> _
>
next prev parent reply other threads:[~2019-01-16 19:16 UTC|newest]
Thread overview: 35+ 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 18:19 ` [PATCH 1/4] mm/resource: return real error codes from walk failures Dave Hansen
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 19:16 ` Jerome Glisse [this message]
2019-01-16 23:01 ` Dave Hansen
2019-01-16 23:38 ` Jerome Glisse
2019-01-23 20:03 ` Dave Hansen
2019-01-23 20:15 ` Jerome Glisse
2019-01-18 19:58 ` Dave Hansen
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 ` [PATCH 4/4] dax: "Hotplug" persistent memory for use like normal RAM Dave Hansen
2019-01-16 21:16 ` Bjorn Helgaas
2019-01-16 21:40 ` Dave Hansen
2019-01-16 21:44 ` Bjorn Helgaas
2019-01-16 22:06 ` Dan Williams
2019-01-16 21:53 ` Dave Hansen
2019-01-16 21:59 ` Bjorn Helgaas
2019-01-16 21:31 ` Dan Williams
2019-01-17 5:21 ` Du, Fan
2019-01-17 16:56 ` Dan Williams
2019-01-17 8:19 ` Yanmin Zhang
2019-01-17 15:17 ` Dave Hansen
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 16:47 ` Keith Busch
2019-01-17 17:20 ` Jeff Moyer
2019-01-17 19:34 ` Keith Busch
2019-01-17 21:57 ` Jeff Moyer
2019-01-18 11:48 ` Fengguang Wu
2019-01-17 16:50 ` Dan Williams
2019-01-17 22:43 ` Dave Hansen
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