Re: [PATCH] vfio/type1: unpin PageReserved page

From: Alex Williamson
Date: Mon Feb 26 2024 - 12:33:12 EST

On Tue, 27 Feb 2024 01:14:54 +0800
Yisheng Xie <ethan.xys@xxxxxxxxxxxxxxxxx> wrote:

> 在 2024/2/27 00:14, Alex Williamson 写道:
> > On Tue, 27 Feb 2024 00:01:06 +0800
> > Yisheng Xie<ethan.xys@xxxxxxxxxxxxxxxxx> wrote:
> >
> >> We meet a warning as following:
> >> WARNING: CPU: 99 PID: 1766859 at mm/gup.c:209 try_grab_page.part.0+0xe8/0x1b0
> >> CPU: 99 PID: 1766859 Comm: qemu-kvm Kdump: loaded Tainted: GOE 5.10134-008.2.x86_64 #1
> > ^^^^^^^^
> >
> > Does this issue reproduce on mainline? Thanks,
>
> I have check the code of mainline, the logical seems the same as my
> version.
>
> so I think it can reproduce if i understand correctly.

I obviously can't speak to what's in your 5.10.134-008.2 kernel, but I
do know there's a very similar issue resolved in v6.0 mainline and
included in v5.10.146 of the stable tree. Please test. Thanks,

Alex

> >> Hardware name: Foxconn AliServer-Thor-04-12U-v2/Thunder2, BIOS 1.0.PL.FC.P.031.00 05/18/2022
> >> RIP: 0010:try_grab_page.part.0+0xe8/0x1b0
> >> Code: b9 00 04 00 00 83 e6 01 74 ca 48 8b 32 b9 00 04 00 00 f7 c6 00 00 01 00 74 ba eb 91 8b 57 34 48 89 f8 85 d2 0f 8f 48 ff ff ff <0f> 0b 31 c0 c3 48 89 fa 48 8b 0a f7 c1 00 00 01 00 0f 85 5c ff ff
> >> RSP: 0018:ffffc900b1a63b98 EFLAGS: 00010282
> >> RAX: ffffea00000e4580 RBX: 0000000000052202 RCX: ffffea00000e4580
> >> RDX: 0000000080000001 RSI: 0000000000052202 RDI: ffffea00000e4580
> >> RBP: ffff88efa5d3d860 R08: 0000000000000000 R09: 0000000000000002
> >> R10: 0000000000000008 R11: ffff89403fff7000 R12: ffff88f589165818
> >> R13: 00007f1320600000 R14: ffffea0181296ca8 R15: ffffea00000e4580
> >> FS: 00007f1324f93e00(0000) GS:ffff893ebfb80000(0000) knlGS:0000000000000000
> >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> CR2: 00007f1321694070 CR3: 0000006046014004 CR4: 00000000007726e0
> >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >> PKRU: 55555554
> >> Call Trace:
> >> follow_page_pte+0x64b/0x800
> >> __get_user_pages+0x228/0x560
> >> __gup_longterm_locked+0xa0/0x2f0
> >> vaddr_get_pfns+0x67/0x100 [vfio_iommu_type1]
> >> vfio_pin_pages_remote+0x30b/0x460 [vfio_iommu_type1]
> >> vfio_pin_map_dma+0xd4/0x2e0 [vfio_iommu_type1]
> >> vfio_dma_do_map+0x21e/0x340 [vfio_iommu_type1]
> >> vfio_iommu_type1_ioctl+0xdd/0x170 [vfio_iommu_type1]
> >> ? __fget_files+0x79/0xb0
> >> ksys_ioctl+0x7b/0xb0
> >> ? ksys_write+0xc4/0xe0
> >> __x64_sys_ioctl+0x16/0x20
> >> do_syscall_64+0x2d/0x40
> >> entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >>
> >> After add dumppage, it shows that it is a PageReserved page(e.g. zero page),
> >> whoes refcount is just overflow:
> >> page:00000000b0504535 refcount:-2147483647 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3916
> >> flags: 0xffffc000001002(referenced|reserved)
> >> raw: 00ffffc000001002 ffffea00000e4588 ffffea00000e4588 0000000000000000
> >> raw: 0000000000000000 0000000000000000 80000001ffffffff 0000000000000000
> >>
> >> gup will _pin_ a page which is PageReserved, however, put_pfn in vfio will
> >> skip unpin page which is PageReserved. So use pfn_valid in put_pfn
> >> instead of !is_invalid_reserved_pfn to unpin PageReserved page.
> >>
> >> Signed-off-by: Yisheng Xie<ethan.xys@xxxxxxxxxxxxxxxxx>
> >> ---
> >> drivers/vfio/vfio_iommu_type1.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> >> index b2854d7939ce..12775bab27ee 100644
> >> --- a/drivers/vfio/vfio_iommu_type1.c
> >> +++ b/drivers/vfio/vfio_iommu_type1.c
> >> @@ -461,7 +461,7 @@ static bool is_invalid_reserved_pfn(unsigned long pfn)
> >>
> >> static int put_pfn(unsigned long pfn, int prot)
> >> {
> >> - if (!is_invalid_reserved_pfn(pfn)) {
> >> + if (pfn_valid(pfn)) {
> >> struct page *page = pfn_to_page(pfn);
> >>
> >> unpin_user_pages_dirty_lock(&page, 1, prot & IOMMU_WRITE);