[resent with correct stable@xxxxxxxxxxxxxxx list] On Tue, Apr 15, 2025 at 08:59:19PM +0200, Salvatore Bonaccorso wrote: > Hi > > [Apologies if this has been reported already but I have not found an > already filled corresponding report] > > After updating from the 6.1.129 based version to 6.1.133, various > users have reported that their VMs do not boot anymore up (both KVM > and under Xen) if pci-passthrough is involved. The reports are at: > > https://bugs.debian.org/1102889 > https://bugs.debian.org/1102914 > https://bugs.debian.org/1103153 > > Milan Broz bisected the issues and found that the commit introducing > the problems can be tracked down to backport of c8070b787519 ("mm: > Don't pin ZERO_PAGE in pin_user_pages()") from 6.5-rc1 which got > backported as 476c1dfefab8 ("mm: Don't pin ZERO_PAGE in > pin_user_pages()") in 6.1.130. See https://bugs.debian.org/1102914#60 > > #regzbot introduced: 476c1dfefab8b98ae9c3e3ad283c2ac10d30c774 > > 476c1dfefab8b98ae9c3e3ad283c2ac10d30c774 is the first bad commit > commit 476c1dfefab8b98ae9c3e3ad283c2ac10d30c774 > Author: David Howells <dhowells@xxxxxxxxxx> > Date: Fri May 26 22:41:40 2023 +0100 > > mm: Don't pin ZERO_PAGE in pin_user_pages() > > [ Upstream commit c8070b78751955e59b42457b974bea4a4fe00187 ] > > Make pin_user_pages*() leave a ZERO_PAGE unpinned if it extracts a pointer > to it from the page tables and make unpin_user_page*() correspondingly > ignore a ZERO_PAGE when unpinning. We don't want to risk overrunning a > zero page's refcount as we're only allowed ~2 million pins on it - > something that userspace can conceivably trigger. > > Add a pair of functions to test whether a page or a folio is a ZERO_PAGE. > > Signed-off-by: David Howells <dhowells@xxxxxxxxxx> > cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> > cc: David Hildenbrand <david@xxxxxxxxxx> > cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx> > cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > cc: Jens Axboe <axboe@xxxxxxxxx> > cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > cc: Jan Kara <jack@xxxxxxx> > cc: Jeff Layton <jlayton@xxxxxxxxxx> > cc: Jason Gunthorpe <jgg@xxxxxxxxxx> > cc: Logan Gunthorpe <logang@xxxxxxxxxxxx> > cc: Hillf Danton <hdanton@xxxxxxxx> > cc: Christian Brauner <brauner@xxxxxxxxxx> > cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > cc: linux-fsdevel@xxxxxxxxxxxxxxx > cc: linux-block@xxxxxxxxxxxxxxx > cc: linux-kernel@xxxxxxxxxxxxxxx > cc: linux-mm@xxxxxxxxx > Reviewed-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx> > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > Acked-by: David Hildenbrand <david@xxxxxxxxxx> > Link: https://lore.kernel.org/r/20230526214142.958751-2-dhowells@xxxxxxxxxx > Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> > Stable-dep-of: bddf10d26e6e ("uprobes: Reject the shared zeropage in uprobe_write_opcode()") > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > > Documentation/core-api/pin_user_pages.rst | 6 ++++++ > include/linux/mm.h | 26 ++++++++++++++++++++++++-- > mm/gup.c | 31 ++++++++++++++++++++++++++++++- > 3 files changed, 60 insertions(+), 3 deletions(-) > > Milan verified that the issue persists in 6.1.134 so far and the patch > itself cannot be just reverted. > > The failures all have a similar pattern, when pci-passthrough is used > for a pci devide, for instance under qemu the bootup will fail with: > > qemu-system-x86_64: -device {"driver":"vfio-pci","host":"0000:03:00.0","id":"hostdev0","bus":"pci.3","addr":"0x0"}: VFIO_MAP_DMA failed: Cannot allocate memory > qemu-system-x86_64: -device {"driver":"vfio-pci","host":"0000:03:00.0","id":"hostdev0","bus":"pci.3","addr":"0x0"}: vfio 0000:03:00.0: failed to setup container > > (in the case as reported by Milan). > > Any ideas here? > > Regards, > Salvatore
