Jason Wang
2023-Aug-02 02:51 UTC
[PATCH] vdpa/mlx5: Fix crash on shutdown for when no ndev exists
On Tue, Aug 1, 2023 at 4:17?PM Dragos Tatulea <dtatulea at 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 at 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 at 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/drivers/net/ethernet/mellanox/mlx5/core/main.c#n2129 > > > > > > > > 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: > > > > https://bugzilla.redhat.com/show_bug.cgi?id=2108406 > > > 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? > > > > > > > > > -- > > > MST > > > > > >
Dragos Tatulea
2023-Aug-02 07:56 UTC
[PATCH] vdpa/mlx5: Fix crash on shutdown for when no ndev exists
On Wed, 2023-08-02 at 10:51 +0800, Jason Wang wrote:> On Tue, Aug 1, 2023 at 4:17?PM Dragos Tatulea <dtatulea at 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 at 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 at 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/drivers/net/ethernet/mellanox/mlx5/core/main.c#n2129 > > > > > > > > > > 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.> > > There used to be bzs that requires virtio drivers to add a shutdown to > > > fix kexec: > > > > > > https://bugzilla.redhat.com/show_bug.cgi?id=2108406 > > > > > 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