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From: David Hildenbrand <david@redhat.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	Dave Young <dyoung@redhat.com>, Baoquan He <bhe@redhat.com>,
	Vivek Goyal <vgoyal@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Keith Busch <keith.busch@intel.com>,
	Michal Hocko <mhocko@suse.com>, Qian Cai <cai@lca.pw>,
	Eric Biederman <ebiederm@xmission.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	x86@kernel.org, kexec@lists.infradead.org
Subject: Re: [PATCH v1 1/3] kernel/resource: make walk_system_ram_res() find all busy IORESOURCE_SYSTEM_RAM resources
Date: Wed, 24 Mar 2021 12:28:21 +0100	[thread overview]
Message-ID: <8aa6af09-6f8b-1f50-820f-90eab0993f1c@redhat.com> (raw)
In-Reply-To: <20210324111835.GA18855@linux>

On 24.03.21 12:18, Oscar Salvador wrote:
> On Mon, Mar 22, 2021 at 05:01:58PM +0100, David Hildenbrand wrote:
>> It used to be true that we can have busy system RAM only on the first level
>> in the resourc tree. However, this is no longer holds for driver-managed
>> system RAM (i.e., added via dax/kmem and virtio-mem), which gets added on
>> lower levels.
> 
> Let me ask some rookie questions:
> 
> What does "busy" term stand for here?

IORESOURCE_BUSY - here: actually added, not just some reserved range / container.


> Why resources coming from virtio-mem are added at a lower levels?

Some information can be had from ebf71552bb0e690cad523ad175e8c4c89a33c333

commit ebf71552bb0e690cad523ad175e8c4c89a33c333
Author: David Hildenbrand <david@redhat.com>
Date:   Thu May 7 16:01:35 2020 +0200

     virtio-mem: Add parent resource for all added "System RAM"
     
     Let's add a parent resource, named after the virtio device (inspired by
     drivers/dax/kmem.c). This allows user space to identify which memory
     belongs to which virtio-mem device.
     
     With this change and two virtio-mem devices:
             :/# cat /proc/iomem
             00000000-00000fff : Reserved
             00001000-0009fbff : System RAM
             [...]
             140000000-333ffffff : virtio0
               140000000-147ffffff : System RAM
               148000000-14fffffff : System RAM
               150000000-157ffffff : System RAM
             [...]
             334000000-3033ffffff : virtio1
               338000000-33fffffff : System RAM
               340000000-347ffffff : System RAM
               348000000-34fffffff : System RAM
             [...]



For dax/kmem it comes naturally due to the "Persistent Memory" and
device parent resources like:

             140000000-33fffffff : Persistent Memory
               140000000-1481fffff : namespace0.0
               150000000-33fffffff : dax0.0
                 150000000-33fffffff : System RAM (kmem)
             3280000000-32ffffffff : PCI Bus 0000:00


Thanks

-- 
Thanks,

David / dhildenb



  reply	other threads:[~2021-03-24 11:28 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-22 16:01 [PATCH v1 0/3] kernel/resource: make walk_system_ram_res() and walk_mem_res() search the whole tree David Hildenbrand
2021-03-22 16:01 ` [PATCH v1 1/3] kernel/resource: make walk_system_ram_res() find all busy IORESOURCE_SYSTEM_RAM resources David Hildenbrand
2021-03-22 16:10   ` Dan Williams
2021-03-23  9:40   ` David Hildenbrand
2021-03-23 11:07     ` Andy Shevchenko
2021-03-23 11:06   ` Andy Shevchenko
2021-03-23 11:25     ` David Hildenbrand
2021-03-23 14:33   ` Baoquan He
2021-03-24 11:18   ` Oscar Salvador
2021-03-24 11:28     ` David Hildenbrand [this message]
2021-03-22 16:01 ` [PATCH v1 2/3] kernel/resource: make walk_mem_res() find all busy IORESOURCE_MEM resources David Hildenbrand
2021-03-22 16:11   ` Dan Williams
2021-03-23 11:08   ` Andy Shevchenko
2021-03-23 11:26     ` David Hildenbrand
2021-03-22 16:02 ` [PATCH v1 3/3] kernel/resource: remove first_lvl / siblings_only logic David Hildenbrand
2021-03-22 16:12   ` Dan Williams
2021-03-23 11:11   ` Andy Shevchenko
2021-03-23 11:19     ` David Hildenbrand
2021-03-23 11:05 ` [PATCH v1 0/3] kernel/resource: make walk_system_ram_res() and walk_mem_res() search the whole tree Andy Shevchenko

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