* + mm-fix-huge-page-table-not-free-after-memory-unplug.patch added to mm-hotfixes-unstable branch
@ 2025-12-23 1:15 Andrew Morton
2025-12-23 8:27 ` David Hildenbrand (Red Hat)
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2025-12-23 1:15 UTC (permalink / raw)
To: mm-commits, rppt, jgg, david, baolu.lu, yuan1.liu, akpm
The patch titled
Subject: mm: fix huge page table not free after memory unplug
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-fix-huge-page-table-not-free-after-memory-unplug.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fix-huge-page-table-not-free-after-memory-unplug.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days
------------------------------------------------------
From: Yuan Liu <yuan1.liu@intel.com>
Subject: mm: fix huge page table not free after memory unplug
Date: Sun, 21 Dec 2025 23:11:17 -0500
Newly plugged memory is marked as prot_sethuge via phys_pmd_init without
setting PG_head. During memory unplug, free_hugepage_table frees the page
table as 2M, but pagetable_free handles it as 4K.
The following test case of memory unplug for a VM [1], tested in the
environment [2], show that results.
+-----------------------+------+------+
|Check System Memory |Plug |Unplug|
|via free -h |256GB |256GB |
+-----------------------+------+------+
| Free 4K page table |257GB |5.6GB |
+-----------------------+------+------+
| Free 2M page table |257GB |1.7GB |
+-----------------------+------+------+
[1] Qemu commands to unhotplug 256G memory for a VM:
object_add memory-backend-ram,id=hotmem0,size=256G,share=on
device_add virtio-mem-pci,id=vmem1,memdev=hotmem0,bus=port1
qom-set vmem1 requested-size 256G (Plug Memory)
qom-set vmem1 requested-size 0G (Unplug Memory)
[2] Hardware : Intel Icelake server
Guest Kernel : v6.19-rc1
Qemu : v9.0.0
Launch VM:
qemu-system-x86_64 -accel kvm -cpu host \
-drive file=./Centos10_cloud.qcow2,format=qcow2,if=virtio \
-drive file=./seed.img,format=raw,if=virtio \
-smp 3,cores=3,threads=1,sockets=1,maxcpus=3 \
-m 2G,slots=10,maxmem=2052472M \
-device pcie-root-port,id=port1,bus=pcie.0,slot=1,multifunction=on \
-device pcie-root-port,id=port2,bus=pcie.0,slot=2 \
-nographic -machine q35 \
-nic user,hostfwd=tcp::3000-:22
Guest kernel auto-onlines newly added memory blocks:
echo online > /sys/devices/system/memory/auto_online_blocks
Link: https://lkml.kernel.org/r/20251222041117.44865-1-yuan1.liu@intel.com
Fixes: bf9e4e30f353 ("x86/mm: use pagetable_free()")
Signed-off-by: Yuan Liu <yuan1.liu@intel.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Baolu Lu <baolu.lu@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
arch/x86/mm/init_64.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/mm/init_64.c~mm-fix-huge-page-table-not-free-after-memory-unplug
+++ a/arch/x86/mm/init_64.c
@@ -1028,7 +1028,7 @@ static void __meminit free_pagetable(str
free_reserved_pages(page, nr_pages);
#endif
} else {
- pagetable_free(page_ptdesc(page));
+ __free_pages(page, order);
}
}
_
Patches currently in -mm which might be from yuan1.liu@intel.com are
mm-fix-huge-page-table-not-free-after-memory-unplug.patch
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: + mm-fix-huge-page-table-not-free-after-memory-unplug.patch added to mm-hotfixes-unstable branch
2025-12-23 1:15 + mm-fix-huge-page-table-not-free-after-memory-unplug.patch added to mm-hotfixes-unstable branch Andrew Morton
@ 2025-12-23 8:27 ` David Hildenbrand (Red Hat)
2025-12-23 20:05 ` Mike Rapoport
0 siblings, 1 reply; 3+ messages in thread
From: David Hildenbrand (Red Hat) @ 2025-12-23 8:27 UTC (permalink / raw)
To: Andrew Morton, mm-commits, rppt, jgg, baolu.lu, yuan1.liu,
Dave Hansen
On 12/23/25 02:15, Andrew Morton wrote:
> The patch titled
> Subject: mm: fix huge page table not free after memory unplug
> has been added to the -mm mm-hotfixes-unstable branch. Its filename is
> mm-fix-huge-page-table-not-free-after-memory-unplug.patch
>
> This patch will shortly appear at
> https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fix-huge-page-table-not-free-after-memory-unplug.patch
>
> This patch will later appear in the mm-hotfixes-unstable branch at
> git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
>
> Before you just go and hit "reply", please:
> a) Consider who else should be cc'ed
> b) Prefer to cc a suitable mailing list as well
> c) Ideally: find the original patch on the mailing list and do a
> reply-to-all to that, adding suitable additional cc's
>
> *** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
>
> The -mm tree is included into linux-next via various
> branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> and is updated there most days
>
> ------------------------------------------------------
> From: Yuan Liu <yuan1.liu@intel.com>
> Subject: mm: fix huge page table not free after memory unplug
> Date: Sun, 21 Dec 2025 23:11:17 -0500
>
> Newly plugged memory is marked as prot_sethuge via phys_pmd_init without
> setting PG_head. During memory unplug, free_hugepage_table frees the page
> table as 2M, but pagetable_free handles it as 4K.
>
> The following test case of memory unplug for a VM [1], tested in the
> environment [2], show that results.
>
> +-----------------------+------+------+
> |Check System Memory |Plug |Unplug|
> |via free -h |256GB |256GB |
> +-----------------------+------+------+
> | Free 4K page table |257GB |5.6GB |
> +-----------------------+------+------+
> | Free 2M page table |257GB |1.7GB |
> +-----------------------+------+------+
>
> [1] Qemu commands to unhotplug 256G memory for a VM:
> object_add memory-backend-ram,id=hotmem0,size=256G,share=on
> device_add virtio-mem-pci,id=vmem1,memdev=hotmem0,bus=port1
> qom-set vmem1 requested-size 256G (Plug Memory)
> qom-set vmem1 requested-size 0G (Unplug Memory)
>
> [2] Hardware : Intel Icelake server
> Guest Kernel : v6.19-rc1
> Qemu : v9.0.0
>
> Launch VM:
> qemu-system-x86_64 -accel kvm -cpu host \
> -drive file=./Centos10_cloud.qcow2,format=qcow2,if=virtio \
> -drive file=./seed.img,format=raw,if=virtio \
> -smp 3,cores=3,threads=1,sockets=1,maxcpus=3 \
> -m 2G,slots=10,maxmem=2052472M \
> -device pcie-root-port,id=port1,bus=pcie.0,slot=1,multifunction=on \
> -device pcie-root-port,id=port2,bus=pcie.0,slot=2 \
> -nographic -machine q35 \
> -nic user,hostfwd=tcp::3000-:22
>
> Guest kernel auto-onlines newly added memory blocks:
> echo online > /sys/devices/system/memory/auto_online_blocks
>
> Link: https://lkml.kernel.org/r/20251222041117.44865-1-yuan1.liu@intel.com
> Fixes: bf9e4e30f353 ("x86/mm: use pagetable_free()")
> Signed-off-by: Yuan Liu <yuan1.liu@intel.com>
> Cc: Jason Gunthorpe <jgg@nvidia.com>
> Cc: Baolu Lu <baolu.lu@linux.intel.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Mike Rapoport <rppt@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> arch/x86/mm/init_64.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/arch/x86/mm/init_64.c~mm-fix-huge-page-table-not-free-after-memory-unplug
> +++ a/arch/x86/mm/init_64.c
> @@ -1028,7 +1028,7 @@ static void __meminit free_pagetable(str
> free_reserved_pages(page, nr_pages);
> #endif
> } else {
> - pagetable_free(page_ptdesc(page));
> + __free_pages(page, order);
Hm, but this way we are skipping deconstructors, no?
In particular, clearing the kernel flag (ptdesc_clear_kernel()) and not
handling ASYNC_KERNEL_PGTABLE_FREE correctly.
--
Cheers
David
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: + mm-fix-huge-page-table-not-free-after-memory-unplug.patch added to mm-hotfixes-unstable branch
2025-12-23 8:27 ` David Hildenbrand (Red Hat)
@ 2025-12-23 20:05 ` Mike Rapoport
0 siblings, 0 replies; 3+ messages in thread
From: Mike Rapoport @ 2025-12-23 20:05 UTC (permalink / raw)
To: David Hildenbrand (Red Hat)
Cc: Andrew Morton, mm-commits, jgg, baolu.lu, yuan1.liu, Dave Hansen
On Tue, Dec 23, 2025 at 09:27:52AM +0100, David Hildenbrand (Red Hat) wrote:
> On 12/23/25 02:15, Andrew Morton wrote:
>
> > From: Yuan Liu <yuan1.liu@intel.com>
> > Subject: mm: fix huge page table not free after memory unplug
> > Date: Sun, 21 Dec 2025 23:11:17 -0500
> >
> > Newly plugged memory is marked as prot_sethuge via phys_pmd_init without
> > setting PG_head. During memory unplug, free_hugepage_table frees the page
> > table as 2M, but pagetable_free handles it as 4K.
> >
> > Link: https://lkml.kernel.org/r/20251222041117.44865-1-yuan1.liu@intel.com
> > Fixes: bf9e4e30f353 ("x86/mm: use pagetable_free()")
> > Signed-off-by: Yuan Liu <yuan1.liu@intel.com>
> > Cc: Jason Gunthorpe <jgg@nvidia.com>
> > Cc: Baolu Lu <baolu.lu@linux.intel.com>
> > Cc: David Hildenbrand <david@redhat.com>
> > Cc: Mike Rapoport <rppt@kernel.org>
> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > ---
> >
> > arch/x86/mm/init_64.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > --- a/arch/x86/mm/init_64.c~mm-fix-huge-page-table-not-free-after-memory-unplug
> > +++ a/arch/x86/mm/init_64.c
> > @@ -1028,7 +1028,7 @@ static void __meminit free_pagetable(str
> > free_reserved_pages(page, nr_pages);
> > #endif
> > } else {
> > - pagetable_free(page_ptdesc(page));
> > + __free_pages(page, order);
>
> Hm, but this way we are skipping deconstructors, no?
>
> In particular, clearing the kernel flag (ptdesc_clear_kernel()) and not
> handling ASYNC_KERNEL_PGTABLE_FREE correctly.
And it seems to be x86 material at any rate.
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2025-12-23 20:05 UTC | newest]
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2025-12-23 1:15 + mm-fix-huge-page-table-not-free-after-memory-unplug.patch added to mm-hotfixes-unstable branch Andrew Morton
2025-12-23 8:27 ` David Hildenbrand (Red Hat)
2025-12-23 20:05 ` Mike Rapoport
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