On Thu, Aug 03, 2023 at 03:02:59PM +0000, Dragos Tatulea wrote:
On Wed, 2023-08-02 at 09:56 +0200, Dragos Tatulea wrote:
On Wed, 2023-08-02 at 10:51 +0800, Jason Wang wrote:
On Tue, Aug 1, 2023 at 4:17 PM Dragos Tatulea dtatulea@nvidia.com wrote:
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 ...
Turns out that this fix (releasing the irqs on .shutdown on mlx5_core) was required for PPC arch but only for certain mainframe systems. That's all the info I could find.
I will send a v2 for this patch that removes the shutdown op. The irqs will be released by the mlx5_core shutdown handler which is responsible for the VF.
Thanks, Dragos
Certainly seems cleaner. Thanks!
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?
This bug might be more accurate:
https://bugzilla.redhat.com/show_bug.cgi?id=1820521
It's about the kexec guys (cced relevant people) wanting to add a shutdown method for virito to fix potential kexec issues.
Thanks
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?
.shutdown could be removed in mlx5_vdpa. But I notice that mlx5_core's .shutdown kicks in from pci_device_shutdown to clean the irqs. So the irqs will still be freed but as a side effect. Which is not good.
Thanks, Dragos