RE: [PATCH 1/1] resource: Fixed iomem resource release failed on release_mem_region_adjustable() when memory node or cpu node hot-remove.

[Guomin Chen]

Hi Toshi
	Thank you for your reply and suggestions.
	I will continue to follow and investigation this issue. thanks 

Thanks and regards


> -----Original Message-----
> From: Kani, Toshi [mailto:toshi.kani@xxxxxxx]
> Sent: 2018å6æ26æ 7:56
> To: Guomin Chen <guomin.chen@xxxxxxxx>; helgaas@xxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; Joey Lee <JLee@xxxxxxxx>; bp@xxxxxxx;
> tglx@xxxxxxxxxxxxx; tiwai@xxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx;
> dan.j.williams@xxxxxxxxx; linux-efi@xxxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx;
> thomas.lendacky@xxxxxxx; brijesh.singh@xxxxxxx;
> baiyaowei@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH 1/1] resource: Fixed iomem resource release failed on
> release_mem_region_adjustable() when memory node or cpu node
> hot-remove.
> 
> On Fri, 2018-06-22 at 18:19 -0500, Bjorn Helgaas wrote:
> > [+cc Toshi]
> >
> > On Fri, Jun 22, 2018 at 08:01:38PM +0800, guomin chen wrote:
> > > We've got a bug report indicating the hot-remove node resource
> > > release failed,when the memory on this node is divided into several
> > > sections.because the release_mem_region_adjustable() can only
> > > release one resource that must be [start,end].
> >
> > Can you please include a URL for the bug report?  That's useful for
> > additional details and gives hints about how future changes in this
> > area might be tested.
> >
> > release_mem_region_adjustable() and the only call to it were added by
> > Toshi (cc'd):
> >
> >   825f787bb496 ("resource: add release_mem_region_adjustable()")
> >   fe74ebb106a5 ("mm: change __remove_pages() to call
> > release_mem_region_adjustable()")
> >
> > > In my case, the BIOS supports faulty memory isolation. if BIOS
> > > detected bad memory block, the BIOS will isolates this badblock.
> > > And set this badblock memory to EfiUnusableMemory in EFI memory map
> > > base on UEFI 2.7 spec.For example in my system, the memory range on
> > > node2 is [mem 0x0000080000000000-0x00000807ffffffff].but the BIOS
> > > detected the [8004e000000-8004e0fffff] is a badblock memory.
> > > So the memory on node2 seem like this:
> > >    		80000000000-8004dffffff : System RAM
> > > 		8004e000000-8004e0fffff : Unusable memory
> > > 		8004e100000-807ffffffff : System RAM
> > >
> > > Now, when offline the cpu node2,the kernel will try to release
> > > ioresource [mem 0x0000080000000000-0x00000807ffffffff]. at this
> > > time, the kernel will release failed,and output error message:
> > > "Unable to release resource <0x0000080000000000-0x00000807ffffffff>
> > > (-22)".
> 
> Hmm... this BIO implementation does not sound right to me.  When EFI
> memory map has a hole, ACPI memory object should have the same hole in its
> resource info.  If so, this node2 memory hot-delete would have requested a
> deletion of 2 separate System RAM ranges, not a single range including this
> hole.  This is also important for memory hot-add.  ACPI memory object needs
> to describe this hole in order for the OS to avoid adding this badblock memory.
> 
> Thanks,
> -Toshi