Re: [PATCH] iommu/vt-d: Fix panic after kexec -p for kdump

[Lu Baolu]

By the way, Joerg Roedel <joro@xxxxxxxxxx> is the IOMMU subsystem
maintainer. If you have a v2, please add his email in the "To" list.

You can always use scripts/get_maintainer.pl to check who should the
patch be sent to. :-)

Best regards,
Baolu

On 10/21/19 3:27 PM, Lu Baolu wrote:
> Hi John,
>
> On 10/18/19 10:17 PM, John Donnelly wrote:
> > This cures a panic on restart after a kexec -p operation on 5.3 and 
> > 5.4 kernels.
> >
> > The underlying state of the iommu registers (iommu->flags &
> > VTD_FLAG_TRANS_PRE_ENABLED) on a restart results in a domain being 
> > marked as
> > "DEFER_DEVICE_DOMAIN_INFO" that produces an Oops in identity_mapping().
> >
> > [ÂÂ 43.654737] BUG: kernel NULL pointer dereference, address:
> > 0000000000000056
> > [ÂÂ 43.655720] #PF: supervisor read access in kernel mode
> > [ÂÂ 43.655720] #PF: error_code(0x0000) - not-present page
> > [ÂÂ 43.655720] PGD 0 P4D 0
> > [ÂÂ 43.655720] Oops: 0000 [#1] SMP PTI
> > [ÂÂ 43.655720] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
> > 5.3.2-1940.el8uek.x86_64 #1
> > [ÂÂ 43.655720] Hardware name: Oracle Corporation ORACLE SERVER
> > X5-2/ASM,MOTHERBOARD,1U, BIOS 30140300 09/20/2018
> > [ÂÂ 43.655720] RIP: 0010:iommu_need_mapping+0x29/0xd0
> > [ÂÂ 43.655720] Code: 00 0f 1f 44 00 00 48 8b 97 70 02 00 00 48 83 fa ff
> > 74 53 48 8d 4a ff b8 01 00 00 00 48 83 f9 fd 76 01 c3 48 8b 35 7f 58 e0
> > 01 <48> 39 72 58 75 f2 55 48 89 e5 41 54 53 48 8b 87 28 02 00 00 4c 8b
> > [ÂÂ 43.655720] RSP: 0018:ffffc9000001b9b0 EFLAGS: 00010246
> > [ÂÂ 43.655720] RAX: 0000000000000001 RBX: 0000000000001000 RCX:
> > fffffffffffffffd
> > [ÂÂ 43.655720] RDX: fffffffffffffffe RSI: ffff8880719b8000 RDI:
> > ffff8880477460b0
> > [ÂÂ 43.655720] RBP: ffffc9000001b9e8 R08: 0000000000000000 R09:
> > ffff888047c01700
> > [ÂÂ 43.655720] R10: 00002194036fc692 R11: 0000000000000000 R12:
> > 0000000000000000
> > [ÂÂ 43.655720] R13: ffff8880477460b0 R14: 0000000000000cc0 R15:
> > ffff888072d2b558
> > [ÂÂ 43.655720] FS:Â 0000000000000000(0000) GS:ffff888071c00000(0000)
> > knlGS:0000000000000000
> > [ÂÂ 43.655720] CS:Â 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ÂÂ 43.655720] CR2: 0000000000000056 CR3: 000000007440a002 CR4:
> > 00000000001606b0
> > [ÂÂ 43.655720] Call Trace:
> > [ÂÂ 43.655720]Â ? intel_alloc_coherent+0x2a/0x180
> > [ÂÂ 43.655720]Â ? __schedule+0x2c2/0x650
> > [ÂÂ 43.655720]Â dma_alloc_attrs+0x8c/0xd0
> > [ÂÂ 43.655720]Â dma_pool_alloc+0xdf/0x200
> > [ÂÂ 43.655720]Â ehci_qh_alloc+0x58/0x130
> > [ÂÂ 43.655720]Â ehci_setup+0x287/0x7ba
> > [ÂÂ 43.655720]Â ? _dev_info+0x6c/0x83
> > [ÂÂ 43.655720]Â ehci_pci_setup+0x91/0x436
> > [ÂÂ 43.655720]Â usb_add_hcd.cold.48+0x1d4/0x754
> > [ÂÂ 43.655720]Â usb_hcd_pci_probe+0x2bc/0x3f0
> > [ÂÂ 43.655720]Â ehci_pci_probe+0x39/0x40
> > [ÂÂ 43.655720]Â local_pci_probe+0x47/0x80
> > [ÂÂ 43.655720]Â pci_device_probe+0xff/0x1b0
> > [ÂÂ 43.655720]Â really_probe+0xf5/0x3a0
> > [ÂÂ 43.655720]Â driver_probe_device+0xbb/0x100
> > [ÂÂ 43.655720]Â device_driver_attach+0x58/0x60
> > [ÂÂ 43.655720]Â __driver_attach+0x8f/0x150
> > [ÂÂ 43.655720]Â ? device_driver_attach+0x60/0x60
> > [ÂÂ 43.655720]Â bus_for_each_dev+0x74/0xb0
> > [ÂÂ 43.655720]Â driver_attach+0x1e/0x20
> > [ÂÂ 43.655720]Â bus_add_driver+0x151/0x1f0
> > [ÂÂ 43.655720]Â ? ehci_hcd_init+0xb2/0xb2
> > [ÂÂ 43.655720]Â ? do_early_param+0x95/0x95
> > [ÂÂ 43.655720]Â driver_register+0x70/0xc0
> > [ÂÂ 43.655720]Â ? ehci_hcd_init+0xb2/0xb2
> > [ÂÂ 43.655720]Â __pci_register_driver+0x57/0x60
> > [ÂÂ 43.655720]Â ehci_pci_init+0x6a/0x6c
> > [ÂÂ 43.655720]Â do_one_initcall+0x4a/0x1fa
> > [ÂÂ 43.655720]Â ? do_early_param+0x95/0x95
> > [ÂÂ 43.655720]Â kernel_init_freeable+0x1bd/0x262
> > [ÂÂ 43.655720]Â ? rest_init+0xb0/0xb0
> > [ÂÂ 43.655720]Â kernel_init+0xe/0x110
> > [ÂÂ 43.655720]Â ret_from_fork+0x24/0x50
>
> Good catch. Can you please add:
>
> Fixes: 8af46c784ecfe ("iommu/vt-d: Implement is_attach_deferred iommu 
> ops entry")
> Cc: stable@xxxxxxxxxxxxxxx # v5.3+
>
> With above:
>
> Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
>
> Best regards,
> Baolu
>
> > Signed-off-by: John Donnelly <john.p.donnelly@xxxxxxxxxx>
> > ---
> > drivers/iommu/intel-iommu.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> > index c4e0e4a9ee9e..f83a9a302f8e 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -2783,7 +2783,7 @@ static int identity_mapping(struct device *dev)
> > ÂÂÂÂstruct device_domain_info *info;
> >
> > ÂÂÂÂinfo = dev->archdata.iommu;
> > -ÂÂÂ if (info && info != DUMMY_DEVICE_DOMAIN_INFO)
> > +ÂÂÂ if (info && info != DUMMY_DEVICE_DOMAIN_INFO && info != 
> > DEFER_DEVICE_DOMAIN_INFO)
> > ÂÂÂÂÂÂÂ return (info->domain == si_domain);
> >
> > ÂÂÂÂreturn 0;