On Tue, 2023-08-01 at 11:59 +0800, Jason Wang wrote:
On Mon, Jul 31, 2023 at 5:08 PM Michael S. Tsirkin mst@redhat.com wrote:
On Mon, Jul 31, 2023 at 07:15:31AM +0000, Dragos Tatulea wrote:
On Thu, 2023-07-27 at 12:28 -0400, Michael S. Tsirkin wrote:
On Thu, Jul 27, 2023 at 04:02:16PM +0000, Dragos Tatulea wrote:
On Wed, 2023-07-26 at 15:26 -0400, Michael S. Tsirkin wrote:
On Wed, Jul 26, 2023 at 10:07:38PM +0300, Dragos Tatulea wrote: > The ndev was accessed on shutdown without a check if it actually > exists. > This triggered the crash pasted below. This patch simply adds a > check > before using ndev. > > BUG: kernel NULL pointer dereference, address: 0000000000000300 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: 0000 [#1] SMP > CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted 6.5.0- > rc2_for_upstream_min_debug_2023_07_17_15_05 #1 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel- > 1.13.0-0- > gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 > RIP: 0010:mlx5v_shutdown+0xe/0x50 [mlx5_vdpa] > RSP: 0018:ffff8881003bfdc0 EFLAGS: 00010286 > RAX: ffff888103befba0 RBX: ffff888109d28008 RCX: 0000000000000017 > RDX: 0000000000000001 RSI: 0000000000000212 RDI: ffff888109d28000 > RBP: 0000000000000000 R08: 0000000d3a3a3882 R09: 0000000000000001 > R10: 0000000000000000 R11: 0000000000000000 R12: ffff888109d28000 > R13: ffff888109d28080 R14: 00000000fee1dead R15: 0000000000000000 > FS: 00007f4969e0be40(0000) GS:ffff88852c800000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000300 CR3: 00000001051cd006 CR4: 0000000000370eb0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <TASK> > ? __die+0x20/0x60 > ? page_fault_oops+0x14c/0x3c0 > ? exc_page_fault+0x75/0x140 > ? asm_exc_page_fault+0x22/0x30 > ? mlx5v_shutdown+0xe/0x50 [mlx5_vdpa] > device_shutdown+0x13e/0x1e0 > kernel_restart+0x36/0x90 > __do_sys_reboot+0x141/0x210 > ? vfs_writev+0xcd/0x140 > ? handle_mm_fault+0x161/0x260 > ? do_writev+0x6b/0x110 > do_syscall_64+0x3d/0x90 > entry_SYSCALL_64_after_hwframe+0x46/0xb0 > RIP: 0033:0x7f496990fb56 > RSP: 002b:00007fffc7bdde88 EFLAGS: 00000206 ORIG_RAX: > 00000000000000a9 > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f496990fb56 > RDX: 0000000001234567 RSI: 0000000028121969 RDI: fffffffffee1dead > RBP: 00007fffc7bde1d0 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 > R13: 00007fffc7bddf10 R14: 0000000000000000 R15: 00007fffc7bde2b8 > </TASK> > CR2: 0000000000000300 > ---[ end trace 0000000000000000 ]--- > > Fixes: bc9a2b3e686e ("vdpa/mlx5: Support interrupt bypassing") > Signed-off-by: Dragos Tatulea dtatulea@nvidia.com > --- > drivers/vdpa/mlx5/net/mlx5_vnet.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c > b/drivers/vdpa/mlx5/net/mlx5_vnet.c > index 9138ef2fb2c8..e2e7ebd71798 100644 > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c > @@ -3556,7 +3556,8 @@ static void mlx5v_shutdown(struct > auxiliary_device > *auxdev) > mgtdev = auxiliary_get_drvdata(auxdev); > ndev = mgtdev->ndev; > > - free_irqs(ndev); > + if (ndev) > + free_irqs(ndev); > } >
something I don't get: irqs are allocated in mlx5_vdpa_dev_add why are they not freed in mlx5_vdpa_dev_del?
That is a good point. I will try to find out. I also don't get why free_irq is called in the vdpa dev .free op instead of mlx5_vdpa_dev_del. Maybe I can change that in a different refactoring.
as it is I have no idea whether e.g. ndev can change between these two call sites. that would make the check pointless.
this is what's creating all this mess.
Not quite: mlx5_vdpa_dev_del (which is a .dev_del of for struct vdpa_mgmtdev_ops) doesn't get called on shutdown. At least that's what I see. Or am I missing something?
and why do we care whether irqs are freed on shutdown?
Had to ask around a bit to find out the answer: there can be issues with kexec IRQ allocation on some platforms. It is documented here [0] for mlx5_core.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/driv...
Thanks, Dragos
It's quite weird. * Some platforms requiring freeing the IRQ's in the shutdown * flow. If they aren't freed they can't be allocated after * kexec. There is no need to cleanup the mlx5_core software * contexts.
but most drivers don't have a shutdown callback how do they work then? do you know which platforms these are?
I don't. x86_64 is not one of them though. I will do some more digging ...
There used to be bzs that requires virtio drivers to add a shutdown to fix kexec:
I don't have access to this. What is it about?
Thanks, Dragos
Thanks
I don't really know much about why shutdown callback is even necessary. I guess this is to detect shutdown and do a faster cleanup than the slow, graceful removal, just cleaning hardware resources?
-- MST