linux-kernel - Re: [regression 6.1.y] Regression from 476c1dfefab8 ("mm: Don't pin ZERO_PAGE in pin_user_pages()") with pci-passthrough for both KVM VMs and booting in xen DomU

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Message-ID: <b872cb3a-f91d-4169-a244-fbefbca5680a@gmail.com>
Date: Tue, 15 Apr 2025 21:11:30 +0200
From: Milan Broz <gmazyland@...il.com>
To: Salvatore Bonaccorso <carnil@...ian.org>,
 David Howells <dhowells@...hat.com>, Christoph Hellwig <hch@...radead.org>,
 David Hildenbrand <david@...hat.com>, Lorenzo Stoakes <lstoakes@...il.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Jens Axboe <axboe@...nel.dk>,
 Al Viro <viro@...iv.linux.org.uk>, Matthew Wilcox <willy@...radead.org>,
 Jan Kara <jack@...e.cz>, Jeff Layton <jlayton@...nel.org>,
 Jason Gunthorpe <jgg@...dia.com>, Logan Gunthorpe <logang@...tatee.com>,
 Hillf Danton <hdanton@...a.com>, Christian Brauner <brauner@...nel.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Sasha Levin <sashal@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 regressions@...ts.linux.dev, table@...r.kernel.org, Bernd Rinn <bb@...n.ch>,
 Karri Hämäläinen <kh.bugreport@...look.com>,
 Cameron Davidson <bugs@...idsoncj.id.au>, Markus <markus@...tz.box>
Subject: Re: [regression 6.1.y] Regression from 476c1dfefab8 ("mm: Don't pin
 ZERO_PAGE in pin_user_pages()") with pci-passthrough for both KVM VMs and
 booting in xen DomU

On 4/15/25 8:59 PM, Salvatore Bonaccorso wrote:
> Milan verified that the issue persists in 6.1.134 so far and the patch
> itself cannot be just reverted.

Just an update:

With 6.1.134 stable as a base, I reverted that commit (upstream c8070b78751955e59b42457b974bea4a4fe00187)
+ applied upstream commit 873aefb376bbc0ed1dd2381ea1d6ec88106fdbd4 (vfio/type1: Unpin zero pages)
+ reverted upstream bddf10d26e6e5114e7415a0e442ec6f51a559468 (uprobes: Reject the shared zeropage in uprobe_write_opcode())
to be able compile code without errors.

With these changes, kernel works with my NVMe passthrough test again. This confirms the issue.

Milan

> 
> 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